diff --git a/.Rbuildignore b/.Rbuildignore
index 29bec85..cc5b1fe 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -3,7 +3,6 @@ CHANGES
 ChangeLog
 TODO
 oChangeLog
-build-prep.sh
 build-release.sh
 src/sp.h.in
 .travis.yml
diff --git a/DESCRIPTION b/DESCRIPTION
index 99b4653..cc7b23c 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,5 +1,5 @@
 Package: sp
-Version: 2.1-4
+Version: 2.2-0
 Title: Classes and Methods for Spatial Data
 Authors@R: c(person("Edzer", "Pebesma", role = c("aut", "cre"),
 				email = "edzer.pebesma@uni-muenster.de"),
diff --git a/README.md b/README.md
index 46ace29..29adcd4 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,8 @@
 
 R Classes and Methods for Spatial Data. Note that this is package will (slowly) be deprecated, in favor of package `sf`. It is in maintenance mode, and currently requires `sf` for coordinate reference system validation and coordinate transformation, conversion and (re)projection.
 
+From version 2.2-0, `sp` has dropped the export of a compiled C API formerly used by `rgdal` and `rgeos`
+
 From version 2.1-0, `sp` has dropped `maptools`, `rgdal` and `rgeos` as suggested packages.
 
 From version 2.0-0, `sp` evolution status is changed to `2L` to use **sf** internally in place of `rgdal`, from default `0L` until now. See [this report](https://r-spatial.org/r/2023/05/15/evolution4.html) for adaptation details, and [this report](https://r-spatial.org/r/2023/04/10/evolution3.html) for progress on retiring `maptools`, `rgdal` and `rgeos`.
diff --git a/build-prep.sh b/build-prep.sh
deleted file mode 100755
index fe452a7..0000000
--- a/build-prep.sh
+++ /dev/null
@@ -1,6 +0,0 @@
-# run before R CMD build sp
-VERSION=`awk '/Version:/{print $2}' DESCRIPTION`
-sed -e 's/@VERSION@/'$VERSION'/' src/sp.h.in > src/sp.h
-cp -p src/sp.h inst/include
-cp -p src/sp_xports.c inst/include
-grep SP_VERSION inst/include/sp.h
diff --git a/build-release.sh b/build-release.sh
index 51f70a6..bbbce06 100755
--- a/build-release.sh
+++ b/build-release.sh
@@ -1,4 +1,3 @@
-sh ./build-prep.sh
 git2cl > xx
 cat xx ChangeLog > inst/ChangeLog
 rm xx
diff --git a/inst/include/sp.h b/inst/include/sp.h
deleted file mode 100644
index 9cf0ede..0000000
--- a/inst/include/sp.h
+++ /dev/null
@@ -1,98 +0,0 @@
-#ifndef R_SP_H
-#define R_SP_H
-
-#ifdef SP_XPORT
-# define SP_PREFIX(name) SP_XPORT(name)
-#else
-# define SP_PREFIX(name) name
-#endif
-/* remember to touch local_stubs.c */
-
-#define SP_VERSION "2.1-4"
-
-#include <R.h>
-/* RSB 091203 */
-#include <Rdefines.h>
-#define R_OFFSET 1
-#include <Rinternals.h>
-#include <Rmath.h>
-
-/* from insiders.c 
-
-int pipbb(double pt1, double pt2, double *bbs);
-int between(double x, double low, double up); 
-SEXP insiders(SEXP n1, SEXP bbs); */
-
-/* from pip.c */
-
-#ifndef MIN
-# define MIN(a,b) ((a)>(b)?(b):(a))
-#endif
-#ifndef MAX
-# define MAX(a,b) ((a)>(b)?(a):(b))
-#endif
-
-#define BUFSIZE 8192
-
-/* polygon structs: */
-typedef struct {
-	double		x, y;
-} PLOT_POINT;
-
-typedef struct {
-	PLOT_POINT	min, max;
-} MBR;
-
-typedef struct polygon {
-	MBR mbr;
-	int lines;
-	PLOT_POINT	*p;
-    int close; /* 1 - is closed polygon */
-} POLYGON;
-
-void setup_poly_minmax(POLYGON *pl);
-char InPoly(PLOT_POINT q, POLYGON *Poly);
-SEXP R_point_in_polygon_sp(SEXP px, SEXP py, SEXP polx, SEXP poly);
-void sarea(double *heights, int *nx, int *ny, double *w, double *h, 
-	double *sa, int *bycell);
-void spRFindCG( int *n, double *x, double *y, double *xc, double *yc, 
-		double *area );
-void sp_gcdist(double *lon1, double *lon2, double *lat1, double *lat2, 
-		double *dist);
-void sp_dists(double *u, double *v, double *uout, double *vout, 
-		int *n, double *dists, int *lonlat);
-void sp_dists_NN(double *u1, double *v1, double *u2, double *v2,
-        int *n, double *dists, int *lonlat);
-void sp_lengths(double *u, double *v, int *n, double *lengths, int *lonlat);
-SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP sp_duplicates(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP pointsInBox(SEXP lb, SEXP px, SEXP py);
-SEXP tList(SEXP nl, SEXP m);
-
-/* RSB 091203 */
-
-#define DIM     2               /* Dimension of points */
-typedef double  tPointd[DIM];   /* type double point */
-
-double  SP_PREFIX(Area2)(const tPointd a, const tPointd b, const tPointd c);
-void    SP_PREFIX(FindCG)(int n, tPointd *P, tPointd CG, double *Areasum2);
-void    SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, 
-	const tPointd p3, tPointd c);
-void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords, 
-	double *xc, double *yc, double *area );
-void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps);
-
-SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP hole);
-SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID);
-SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO, const SEXP p4s);
-SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls);
-SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_getIDs_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls);
-SEXP SP_PREFIX(comment2comm)(const SEXP obj);
-SEXP SP_PREFIX(sp_linkingTo_version)(void);
-#endif
-/* remember to touch local_stubs.c */
-
diff --git a/inst/include/sp_xports.c b/inst/include/sp_xports.c
deleted file mode 100644
index 0155287..0000000
--- a/inst/include/sp_xports.c
+++ /dev/null
@@ -1,677 +0,0 @@
-#define USING_R 1
-
-#include "sp.h"
-/* remember to touch local_stubs.c */
-
-SEXP SP_PREFIX(sp_linkingTo_version)(void) {
-    SEXP ans;
-    PROTECT(ans = NEW_CHARACTER(1));
-    SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING(SP_VERSION));
-    UNPROTECT(1);
-    return(ans);
-}
-
-SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
-
-    SEXP SPans, labpt, Area, ringDir, hole, cls;
-    double area, xc, yc;
-    double *x, *y;
-    int pc=0, rev=FALSE;
-    int i, ii, nn=INTEGER_POINTER(n)[0];
-    SEXP valid;
-    SEXP ccopy,  /* copy of coords to go into returned structure */
-        dim1;
-
-    for (i=0; i<nn; i++) {
-       if(!R_FINITE(NUMERIC_POINTER(coords)[i]))
-           error("non-finite x coordinate");
-       if(!R_FINITE(NUMERIC_POINTER(coords)[i+nn]))
-           error("non-finite y coordinate");
-    }
-
-// 140406 ring closure
-    if (NUMERIC_POINTER(coords)[0] != NUMERIC_POINTER(coords)[nn-1]
-        || NUMERIC_POINTER(coords)[nn] != NUMERIC_POINTER(coords)[(2*nn)-1]) {
-        PROTECT(ccopy = NEW_NUMERIC((nn+1)*2)); pc++;
-        PROTECT(dim1 = NEW_INTEGER(2)); pc++;
-        for (i=0; i<nn; i++) {
-            NUMERIC_POINTER(ccopy)[i] = NUMERIC_POINTER(coords)[i];
-            NUMERIC_POINTER(ccopy)[i+(nn+1)] = NUMERIC_POINTER(coords)[i+nn];
-        }
-        NUMERIC_POINTER(ccopy)[nn] = NUMERIC_POINTER(coords)[0];
-        NUMERIC_POINTER(ccopy)[(2*(nn+1))-1] = NUMERIC_POINTER(coords)[nn];
-        nn++;
-        INTEGER_POINTER(dim1)[0] = nn;
-        INTEGER_POINTER(dim1)[1] = 2;
-        setAttrib(ccopy, R_DimSymbol, dim1);
-    } else {
-		if (MAYBE_REFERENCED(coords)) {
-			PROTECT(ccopy = duplicate(coords)); 
-			pc++;
-		} else 
-			ccopy = coords; 
-	}
-
-	/* from here one, ccopy is closed, and can be modified */
-
-    /* SP_PREFIX(spRFindCG_c)(n, ccopy, &xc, &yc, &area); */
-    SP_PREFIX(spRFindCG_c)(getAttrib(ccopy, R_DimSymbol), ccopy, &xc, &yc, &area);
-    if (fabs(area) < DBL_EPSILON) {
-        if (!R_FINITE(xc) || !R_FINITE(yc)) {
-            if (nn == 1) {
-                xc = NUMERIC_POINTER(ccopy)[0];
-                yc = NUMERIC_POINTER(ccopy)[1];
-            } else if (nn == 2) {
-              xc = (NUMERIC_POINTER(ccopy)[0]+NUMERIC_POINTER(ccopy)[1])/2.0;
-              yc = (NUMERIC_POINTER(ccopy)[2]+NUMERIC_POINTER(ccopy)[3])/2.0;
-            } else if (nn > 2) {
-              xc = (NUMERIC_POINTER(ccopy)[0] +
-                NUMERIC_POINTER(ccopy)[(nn-1)])/2.0;
-              yc = (NUMERIC_POINTER(ccopy)[nn] +
-                NUMERIC_POINTER(ccopy)[nn+(nn-1)])/2.0;
-            }
-        }
-    }
-
-// rchk MAKE_CLASS allocates RSB 180602
-    PROTECT(cls = MAKE_CLASS("Polygon")); pc++;
-    PROTECT(SPans = NEW_OBJECT(cls)); pc++; 
-    PROTECT(ringDir = NEW_INTEGER(1)); pc++;
-    INTEGER_POINTER(ringDir)[0] = (area > 0.0) ? -1 : 1;
-// -1 cw hole, 1 ccw not-hole
-
-/* RSB 100126 fixing hole assumption
- thanks to Javier Munoz for report */
-
-    if (INTEGER_POINTER(ihole)[0] == NA_INTEGER) { // trust ring direction
-        if (INTEGER_POINTER(ringDir)[0] == 1)
-            INTEGER_POINTER(ihole)[0] = 0;
-        else if (INTEGER_POINTER(ringDir)[0] == -1)
-            INTEGER_POINTER(ihole)[0] = 1;
-    } else { // trust hole
-        if (INTEGER_POINTER(ihole)[0] == 1 && 
-            INTEGER_POINTER(ringDir)[0] == 1) {
-            rev = TRUE;
-            INTEGER_POINTER(ringDir)[0] = -1;
-        }
-        if (INTEGER_POINTER(ihole)[0] == 0 && 
-            INTEGER_POINTER(ringDir)[0] == -1) {
-            rev = TRUE;
-            INTEGER_POINTER(ringDir)[0] = 1;
-        }
-    }
-    PROTECT(hole = NEW_LOGICAL(1)); pc++;
-    if (INTEGER_POINTER(ihole)[0] == 1) LOGICAL_POINTER(hole)[0] = TRUE;
-    else LOGICAL_POINTER(hole)[0] = FALSE;
-
-    if (rev) {
-        x = (double *) R_alloc((size_t) nn, sizeof(double));
-        y = (double *) R_alloc((size_t) nn, sizeof(double));
-       for (i=0; i<nn; i++) {
-           x[i] = NUMERIC_POINTER(ccopy)[i];
-           y[i] = NUMERIC_POINTER(ccopy)[i+nn];
-       }
-       for (i=0; i<nn; i++) {
-           ii = (nn-1)-i;
-           NUMERIC_POINTER(ccopy)[ii] = x[i];
-           NUMERIC_POINTER(ccopy)[ii+nn] = y[i];
-       }
-    }
-
-    SET_SLOT(SPans, install("coords"), ccopy);
-
-    PROTECT(labpt = NEW_NUMERIC(2)); pc++;
-    NUMERIC_POINTER(labpt)[0] = xc;
-    NUMERIC_POINTER(labpt)[1] = yc;
-    SET_SLOT(SPans, install("labpt"), labpt);
-
-    PROTECT(Area = NEW_NUMERIC(1)); pc++;
-    NUMERIC_POINTER(Area)[0] = fabs(area);
-    SET_SLOT(SPans, install("area"), Area);
-
-    SET_SLOT(SPans, install("hole"), hole);
-    SET_SLOT(SPans, install("ringDir"), ringDir);
-
-    PROTECT(valid = SP_PREFIX(Polygon_validate_c)(SPans)); pc++;
-
-    if (! isLogical(valid)) {
-        UNPROTECT(pc);
-		/*
-        if (isString(valid)) 
-			error(CHAR(STRING_ELT(valid, 0)));
-        else 
-		*/
-			error("invalid Polygon object");
-    }
-
-    UNPROTECT(pc);
-    return(SPans);
-}
-
-SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj) {
-
-    int pc=0;
-    int n;
-    SEXP coords, labpt, ans;
-
-    coords = GET_SLOT(obj, install("coords"));
-    n = INTEGER_POINTER(getAttrib(coords, R_DimSymbol))[0];
-    if (NUMERIC_POINTER(coords)[0] != NUMERIC_POINTER(coords)[n-1]
-        || NUMERIC_POINTER(coords)[n] != NUMERIC_POINTER(coords)[(2*n)-1]) {
-       PROTECT(ans = NEW_CHARACTER(1)); pc++;
-       SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("ring not closed"));
-       UNPROTECT(pc);
-       return(ans);
-    }
-    labpt = GET_SLOT(obj, install("labpt"));
-    if (!R_FINITE(NUMERIC_POINTER(labpt)[0]) ||
-        !R_FINITE(NUMERIC_POINTER(labpt)[1])) {
-        PROTECT(ans = NEW_CHARACTER(1)); pc++;
-        SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("infinite label point"));
-       UNPROTECT(pc);
-       return(ans);
-    }
-    PROTECT(ans = NEW_LOGICAL(1)); pc++;
-    LOGICAL_POINTER(ans)[0] = TRUE;
-    UNPROTECT(pc);
-    return(ans);
-}
-
-SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
-
-    SEXP ans, labpt, Area, plotOrder, crds, pl, n, hole, pls1, ID1, cls;
-    int nps, i, pc=0, sumholes;
-    double *areas, *areaseps, fuzz;
-    int *po, *holes;
-    SEXP valid;
-
-	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls)); 
-		pc++;
-	} else 
-		pls1 = pls; 
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
-	if (MAYBE_REFERENCED(ID)) {
-		PROTECT(ID1 = duplicate(ID)); 
-		pc++;
-	} else 
-		ID1 = ID; 
-    // PROTECT(ID1 = MAYBE_REFERENCED(ID) ? duplicate(ID) : ID); pc++;
-
-    nps = length(pls1);
-    fuzz = R_pow(DBL_EPSILON, (2.0/3.0));
-    areas = (double *) R_alloc((size_t) nps, sizeof(double));
-    areaseps = (double *) R_alloc((size_t) nps, sizeof(double));
-    holes = (int *) R_alloc((size_t) nps, sizeof(int));
-
-    for (i=0, sumholes=0; i<nps; i++) {
-        areas[i] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("area")))[0]; 
-        holes[i] = LOGICAL_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("hole")))[0];
-         areaseps[i] = holes[i] ? areas[i] + fuzz : areas[i];
-         sumholes += holes[i];
-    }
-    po = (int *) R_alloc((size_t) nps, sizeof(int));
-    if (nps > 1) {
-        for (i=0; i<nps; i++)
-			po[i] = i + R_OFFSET;
-        revsort(areaseps, po, nps);
-    } else
-        po[0] = 1;
-
-    if (sumholes == nps) {
-        crds = GET_SLOT(VECTOR_ELT(pls1, (po[0] - R_OFFSET)),
-            install("coords"));
-        PROTECT(n = NEW_INTEGER(1)); pc++;
-        INTEGER_POINTER(n)[0] = INTEGER_POINTER(getAttrib(crds,
-            R_DimSymbol))[0];
-        PROTECT(hole = NEW_LOGICAL(1)); pc++;
-        LOGICAL_POINTER(hole)[0] = FALSE;
-        pl = SP_PREFIX(Polygon_c)(crds, n, hole);
-/* bug 100417 Patrick Giraudoux */
-        holes[po[0] - R_OFFSET] = LOGICAL_POINTER(hole)[0];
-        SET_VECTOR_ELT(pls1, (po[0] - R_OFFSET), pl);
-    }
-
-// rchk MAKE_CLASS allocates RSB 180602
-    PROTECT(cls = MAKE_CLASS("Polygons")); pc++;
-    PROTECT(ans = NEW_OBJECT(cls)); pc++;
-    SET_SLOT(ans, install("Polygons"), pls1);
-    SET_SLOT(ans, install("ID"), ID1);
-
-    PROTECT(Area = NEW_NUMERIC(1)); pc++;
-    NUMERIC_POINTER(Area)[0] = 0.0;
-    for (i=0; i<nps; i++)
-        NUMERIC_POINTER(Area)[0] += holes[i] ? 0.0 : fabs(areas[i]);
-
-    SET_SLOT(ans, install("area"), Area);
-
-    PROTECT(plotOrder = NEW_INTEGER(nps)); pc++;
-    for (i=0; i<nps; i++)
-		INTEGER_POINTER(plotOrder)[i] = po[i];
-
-    SET_SLOT(ans, install("plotOrder"), plotOrder);
-
-    PROTECT(labpt = NEW_NUMERIC(2)); pc++;
-    NUMERIC_POINTER(labpt)[0] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1,
-        (po[0]-1)), install("labpt")))[0];
-    NUMERIC_POINTER(labpt)[1] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1,
-        (po[0]-1)), install("labpt")))[1];
-    SET_SLOT(ans, install("labpt"), labpt);
-
-    PROTECT(valid = SP_PREFIX(Polygons_validate_c)(ans)); pc++;
-    if (!isLogical(valid)) {
-        UNPROTECT(pc);
-		/*
-        if (isString(valid)) 
-			error(CHAR(STRING_ELT(valid, 0)));
-        else
-		*/
-			error("invalid Polygons object");
-    }
-
-    UNPROTECT(pc);
-    return(ans);
-}
-
-SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj) {
-
-    int pc=0;
-    int i, n;
-    SEXP Pls, labpt, ans;
-    char *cls="Polygon";
-
-    PROTECT(Pls = GET_SLOT(obj, install("Polygons"))); pc++;
-    n = length(Pls);
-    for (i=0; i<n; i++) {
-        if (strcmp(CHAR(STRING_ELT(getAttrib(VECTOR_ELT(Pls, i),
-           R_ClassSymbol), 0)), cls) != 0) {
-              PROTECT(ans = NEW_CHARACTER(1)); pc++;
-              SET_STRING_ELT(ans, 0,
-              COPY_TO_USER_STRING("Polygons slot contains non-Polygon object"));
-              UNPROTECT(pc);
-              return(ans);
-        }
-    }
-
-    if (n != length(GET_SLOT(obj, install("plotOrder")))) {
-        PROTECT(ans = NEW_CHARACTER(1)); pc++;
-        SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("plotOrder and Polygons differ in length"));
-        UNPROTECT(pc);
-        return(ans);
-    }
-
-    labpt = GET_SLOT(obj, install("labpt"));
-    if (!R_FINITE(NUMERIC_POINTER(labpt)[0]) ||
-      !R_FINITE(NUMERIC_POINTER(labpt)[1])) {
-      PROTECT(ans = NEW_CHARACTER(1)); pc++;
-      SET_STRING_ELT(ans, 0,
-         COPY_TO_USER_STRING("infinite label point"));
-      UNPROTECT(pc);
-      return(ans);
-    }
-    PROTECT(ans = NEW_LOGICAL(1)); pc++;
-    LOGICAL_POINTER(ans)[0] = TRUE;
-    UNPROTECT(pc);
-    return(ans);
-
-}
-
-SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO, 
-		const SEXP p4s) {
-
-    SEXP ans, bbox, ppO, cls;
-    int pc=0;
-
-// rchk MAKE_CLASS allocates RSB 180602
-    PROTECT(cls = MAKE_CLASS("SpatialPolygons")); pc++;
-    PROTECT(ans = NEW_OBJECT(cls)); pc++;
-    // SET_SLOT(ans, install("polygons"), MAYBE_REFERENCED(pls) ? duplicate(pls) : pls);
-    SET_SLOT(ans, install("polygons"), pls);
-    // SET_SLOT(ans, install("proj4string"), MAYBE_REFERENCED(p4s) ? duplicate(p4s) : p4s);
-    SET_SLOT(ans, install("proj4string"), p4s);
-
-    if (pO == R_NilValue) {
-		PROTECT(ppO = SP_PREFIX(SpatialPolygons_plotOrder_c)(pls));
-		pc++;
-    } else
-		ppO = pO;
-    // SET_SLOT(ans, install("plotOrder"), MAYBE_REFERENCED(pO) ? duplicate(pO) : pO);
-    SET_SLOT(ans, install("plotOrder"), ppO);
-
-    PROTECT(bbox = SP_PREFIX(bboxCalcR_c(pls))); pc++;
-    SET_SLOT(ans, install("bbox"), bbox);
-
-    UNPROTECT(pc);
-    return(ans);
-
-}
-
-SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls) {
-
-    SEXP plotOrder, pls1;
-    int pc=0, ng, i;
-    int *po;
-    double *areas;
-
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
-	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls));
-		pc++;
-	} else
-		pls1 = pls;
-
-    ng = length(pls1);
-    areas = (double *) R_alloc((size_t) ng, sizeof(double));
-    po = (int *) R_alloc((size_t) ng, sizeof(int));
-    for (i=0; i<ng; i++) {
-        areas[i] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("area")))[0]; 
-        po[i] = i + R_OFFSET;
-    }
-    revsort(areas, po, ng);
-    PROTECT(plotOrder = NEW_INTEGER(ng)); pc++;
-    for (i=0; i<ng; i++)
-		INTEGER_POINTER(plotOrder)[i] = po[i];
-
-    UNPROTECT(pc);
-    return(plotOrder);
-
-}
-
-SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj) {
-
-    int pc=0;
-    int i, n;
-    SEXP pls, ans;
-    char *cls="Polygons";
-
-    PROTECT(pls = GET_SLOT(obj, install("polygons"))); pc++;
-    n = length(pls);
-    for (i=0; i<n; i++) {
-        if (strcmp(CHAR(STRING_ELT(getAttrib(VECTOR_ELT(pls, i),
-           R_ClassSymbol), 0)), cls) != 0) {
-             PROTECT(ans = NEW_CHARACTER(1)); pc++;
-             SET_STRING_ELT(ans, 0,
-             COPY_TO_USER_STRING("polygons slot contains non-Polygons object"));
-             UNPROTECT(pc);
-             return(ans);
-        }
-    }
-
-    if (n != length(GET_SLOT(obj, install("plotOrder")))) {
-        PROTECT(ans = NEW_CHARACTER(1)); pc++;
-        SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("plotOrder and polygons differ in length"));
-        UNPROTECT(pc);
-        return(ans);
-    }
-
-    PROTECT(ans = NEW_LOGICAL(1)); pc++;
-    LOGICAL_POINTER(ans)[0] = TRUE;
-    UNPROTECT(pc);
-    return(ans);
-
-}
-
-SEXP SP_PREFIX(SpatialPolygons_getIDs_c)(const SEXP obj) {
-
-    int pc=0;
-    int i, n;
-    SEXP pls, IDs, obj1;
-
-    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? duplicate(obj) : obj); pc++;
-	if (MAYBE_REFERENCED(obj)) {
-		PROTECT(obj1 = duplicate(obj));
-		pc++;
-	} else
-		obj1 = obj;
-
-    PROTECT(pls = GET_SLOT(obj, install("polygons"))); pc++;
-    n = length(pls);
-    PROTECT(IDs = NEW_CHARACTER(n)); pc++;
-    for (i=0; i<n; i++)
-        SET_STRING_ELT(IDs, i, STRING_ELT(GET_SLOT(VECTOR_ELT(pls, i),
-            install("ID")), 0));
-      
-    UNPROTECT(pc);
-    return(IDs);
-
-}
-
-SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls) {
-
-    SEXP ans, dim, dimnames, Pl, crds, pls1;
-    double UX=-DBL_MAX, LX=DBL_MAX, UY=-DBL_MAX, LY=DBL_MAX;
-    int i, j, k, n, npls, npl, pc=0;
-    double x, y;
-
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
-	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls));
-		pc++;
-	} else
-		pls1 = pls;
-
-    npls = length(pls1);
-	if (npls == 0) { /* EJP: this makes a zero-length object at least pass further sanity checks */
-		UX = UY = DBL_MAX;
-		LX = LY = -DBL_MAX;
-	} else for (i=0; i<npls; i++) {
-        Pl = GET_SLOT(VECTOR_ELT(pls1, i), install("Polygons"));
-        npl = length(Pl);
-        for (j=0; j<npl; j++) {
-            crds = GET_SLOT(VECTOR_ELT(Pl, j), install("coords"));
-            n = INTEGER_POINTER(getAttrib(crds, R_DimSymbol))[0];
-            for (k=0; k<n; k++) {
-               x = NUMERIC_POINTER(crds)[k];
-               y = NUMERIC_POINTER(crds)[k+n];
-               if (x > UX) UX = x;
-               if (y > UY) UY = y;
-               if (x < LX) LX = x;
-               if (y < LY) LY = y;
-            }
-        }
-    }
-
-    PROTECT(ans = NEW_NUMERIC(4)); pc++;
-    NUMERIC_POINTER(ans)[0] = LX;
-    NUMERIC_POINTER(ans)[1] = LY;
-    NUMERIC_POINTER(ans)[2] = UX;
-    NUMERIC_POINTER(ans)[3] = UY;
-    PROTECT(dim = NEW_INTEGER(2)); pc++;
-    INTEGER_POINTER(dim)[0] = 2;
-    INTEGER_POINTER(dim)[1] = 2;
-    setAttrib(ans, R_DimSymbol, dim);
-    PROTECT(dimnames = NEW_LIST(2)); pc++;
-    SET_VECTOR_ELT(dimnames, 0, NEW_CHARACTER(2));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 0, COPY_TO_USER_STRING("x"));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 1, COPY_TO_USER_STRING("y"));
-    SET_VECTOR_ELT(dimnames, 1, NEW_CHARACTER(2));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 0, COPY_TO_USER_STRING("min"));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 1, COPY_TO_USER_STRING("max"));
-    setAttrib(ans, R_DimNamesSymbol, dimnames);
-    UNPROTECT(pc);
-    return(ans);
-
-}
-
-void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords, 
-		double *xc, double *yc, double *area ) {
-
-	int i, nn;
-	tPointd *P;
-	tPointd CG;
-	double Areasum2;
-
-	nn = INTEGER_POINTER(n)[0];
-	P = (tPointd *) R_alloc((size_t) nn, sizeof(tPointd));
-	for (i=0; i<nn; i++) {
-		P[i][0] = NUMERIC_POINTER(coords)[i];
-		P[i][1] = NUMERIC_POINTER(coords)[i+nn];
-	}
-	SP_PREFIX(FindCG)(nn, P, CG, &Areasum2);
-	xc[0] = CG[0];
-	yc[0] = CG[1];
-	area[0] = Areasum2/2;
-	return;
-}
-
-void SP_PREFIX(FindCG)( int n, tPointd *P, tPointd CG, double *Areasum2) {
-	int     i;
-	double  A2;        /* Partial area sum */    
-	tPointd Cent3;
-
-	CG[0] = 0;
-	CG[1] = 0;
-	Areasum2[0] = 0;
-	for (i = 1; i < n-1; i++) {
-		SP_PREFIX(Centroid3)( P[0], P[i], P[i+1], Cent3 );
-		A2 =  SP_PREFIX(Area2)( P[0], P[i], P[i+1]);
-		CG[0] += A2 * Cent3[0];
-		CG[1] += A2 * Cent3[1];
-		Areasum2[0] += A2;
-	}
-	CG[0] /= 3 * Areasum2[0];
-	CG[1] /= 3 * Areasum2[0];
-	return;
-}
-/*
-	Returns three times the centroid.  The factor of 3 is
-	left in to permit division to be avoided until later.
-*/
-void SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, const tPointd p3, 
-	tPointd c) {
-        c[0] = p1[0] + p2[0] + p3[0];
-        c[1] = p1[1] + p2[1] + p3[1];
-	return;
-}
-/* 
-        Returns twice the signed area of the triangle determined by a,b,c,
-        positive if a,b,c are oriented ccw, and negative if cw.
-*/
-double SP_PREFIX(Area2)(const tPointd a, const tPointd b, const tPointd c) {
-	double area;
-	area = (b[0] - a[0]) * (c[1] - a[1]) - (c[0] - a[0]) * (b[1] - a[1]);
-	return(area);
-}
-
-
-SEXP SP_PREFIX(comment2comm)(const SEXP obj) {
-    SEXP ans, comment, obj1;
-    int pc=0, ns, i, j, jj, k, nc;
-    char s[15], *buf;
-    int *c, *nss, *co, *coo;
-
-    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? duplicate(obj) : obj); pc++;
-	if (MAYBE_REFERENCED(obj)) {
-		PROTECT(obj1 = duplicate(obj));
-		pc++;
-	} else
-		obj1 = obj;
-
-    PROTECT(comment = getAttrib(obj1, install("comment"))); pc++;
-    if (comment == R_NilValue) {
-        UNPROTECT(pc);
-        return(R_NilValue);
-    }
-
-    nc = length(STRING_ELT(comment, 0));
-    if (nc < 1) error("comment2comm: empty string comment");
-
-    buf = (char *) R_alloc((size_t) (nc+1), sizeof(char));
-
-    strcpy(buf, CHAR(STRING_ELT(comment, 0)));
-
-    i = 0;
-    ns = 0;
-    while (buf[i] != '\0') {
-        if (buf[i] == ' ') ns++;
-        i++;
-    }
-    k = (int) strlen(buf);
-
-   
-    nss = (int *) R_alloc((size_t) (ns+1), sizeof(int));
-    c = (int *) R_alloc((size_t) (ns+1), sizeof(int));
-    i = 0;
-    j = 0;
-    while (buf[i] != '\0') {
-        if (buf[i] == ' ') {
-            nss[j] = i; j++;
-        }
-        i++;
-    }
-    nss[(ns)] = k;
-
-    s[0] = '\0';
-    if (nss[0] > 15) error("comment2comm: buffer overflow");
-    strncpy(s, &buf[0], (size_t) nss[0]);
-    s[nss[0]] = '\0';
-
-    c[0] = atoi(s);
-    for (i=0; i<ns; i++) {
-        k = nss[(i+1)]-(nss[i]+1);
-        if (k > 15) error("comment2comm: buffer overflow");
-        strncpy(s, &buf[(nss[i]+1)], (size_t) k);
-        s[k] = '\0';
-        c[i+1] = atoi(s);
-    }
-
-    for (i=0, k=0; i<(ns+1); i++) if (c[i] == 0) k++;
-    
-    PROTECT(ans = NEW_LIST((k))); pc++;
-    co = (int *) R_alloc((size_t) k, sizeof(int));
-    coo = (int *) R_alloc((size_t) k, sizeof(int));
-    for (i=0; i<k; i++) co[i] = 1;
-
-    for (i=0, j=0; i<(ns+1); i++)
-        if (c[i] == 0) coo[j++] = i + R_OFFSET;
-
-    for (i=0; i<k; i++)
-        for (j=0; j<(ns+1); j++)
-            if ((c[j]) == coo[i]) co[i]++;
-
-    for (i=0; i<k; i++) SET_VECTOR_ELT(ans, i, NEW_INTEGER(co[i]));
-
-    for (i=0; i<k; i++) {
-        jj = 0;
-        INTEGER_POINTER(VECTOR_ELT(ans, i))[jj++] = coo[i];
-        if (co[i] > 1) {
-            for (j=0; j<(ns+1); j++)
-                if (c[j] == coo[i])
-                    INTEGER_POINTER(VECTOR_ELT(ans, i))[jj++] = j + R_OFFSET;
-        }
-    }
-
-    UNPROTECT(pc);
-    return(ans);
-}
-
-void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps) {
-    char cbuf[15];
-    int i, nc, nc1, pr;
-
-    nc = (int) (ceil(log10(nps)+1.0)+1.0);
-    nc1 = (nc*nps)+1;
-    if (bufsiz < nc1) error("comm2comment: buffer overflow");
-
-    pr = snprintf(buf, bufsiz, "%d", comm[0]);
-    bufsiz -= pr;
-    for (i = 1; i < nps; i++) {
-        snprintf(cbuf, 15, " %d", comm[i]);
-        if (strlen(cbuf) >= bufsiz)
-            error("comm2comment: buffer overflow");
-        strncat(buf, cbuf, bufsiz);
-        bufsiz -= strlen(cbuf);
-    }
-    strcat(buf, "\0");
-    return;
-}
-
-/* remember to touch local_stubs.c */
diff --git a/src/gcdist.c b/src/gcdist.c
index 33d4cc0..ba25d96 100644
--- a/src/gcdist.c
+++ b/src/gcdist.c
@@ -46,7 +46,7 @@ void sp_dists_NN(double *u1, double *v1, double *u2, double *v2,
 void sp_lengths(double *u, double *v, int *n, double *lengths, int *lonlat) {
 	int N = *n, j;
 	double gc[1];
-        if (N < 2) error("N less than 2");
+        if (N < 2) Rf_error("N less than 2");
 		
 	if (lonlat[0] == 0)
 		for (j=0; j < N-1; j++) 
diff --git a/src/init.c b/src/init.c
index a9ffa79..fa567f1 100644
--- a/src/init.c
+++ b/src/init.c
@@ -39,7 +39,7 @@ static R_CallMethodDef CallEntries[] = {
     {"SpatialPolygons_getIDs_c", (DL_FUNC) &SpatialPolygons_getIDs_c, 1},
     {"SpatialPolygons_plotOrder_c", (DL_FUNC) &SpatialPolygons_plotOrder_c, 1},
     {"comment2comm", (DL_FUNC) &comment2comm, 1},
-    {"sp_linkingTo_version", (DL_FUNC) &sp_linkingTo_version, 0},
+/*    {"sp_linkingTo_version", (DL_FUNC) &sp_linkingTo_version, 0}, */
     {NULL, NULL, 0}
 };
 
diff --git a/src/pip2.c b/src/pip2.c
index ee2af1c..5c7a999 100644
--- a/src/pip2.c
+++ b/src/pip2.c
@@ -14,17 +14,17 @@ SEXP tList(const SEXP nl, const SEXP m);
 
 
 SEXP tList(const SEXP nl, const SEXP m0) {
-    int n=length(nl), m=INTEGER_POINTER(m0)[0], i, ii, j, jj, *k, pc=0;
+    int n=Rf_length(nl), m=INTEGER_POINTER(m0)[0], i, ii, j, jj, *k, pc=0;
     SEXP res;
     PROTECT(res = NEW_LIST(m)); pc++;
     k = (int *) R_alloc((size_t) m, sizeof(int));
     for (j=0; j<m; j++) k[j] = 0;
     for (i=0; i<n; i++) {
-        ii = length(VECTOR_ELT(nl, i));
+        ii = Rf_length(VECTOR_ELT(nl, i));
         if (ii > 0) {
             for (j=0; j<ii; j++) {
                 jj = INTEGER_POINTER(VECTOR_ELT(nl, i))[j] - ROFFSET;
-                if (jj < 0 || jj >= m) error("invalid indices");
+                if (jj < 0 || jj >= m) Rf_error("invalid indices");
                 k[jj]++;
             }
         }
@@ -32,7 +32,7 @@ SEXP tList(const SEXP nl, const SEXP m0) {
     for (j=0; j<m; j++) SET_VECTOR_ELT(res, j, NEW_INTEGER(k[j]));
     for (j=0; j<m; j++) k[j] = 0;
     for (i=0; i<n; i++) {
-        ii = length(VECTOR_ELT(nl, i));
+        ii = Rf_length(VECTOR_ELT(nl, i));
         if (ii > 0) {
             for (j=0; j<ii; j++) {
                 jj = INTEGER_POINTER(VECTOR_ELT(nl, i))[j] - ROFFSET;
@@ -46,27 +46,27 @@ SEXP tList(const SEXP nl, const SEXP m0) {
 }
 
 SEXP pointsInBox(const SEXP lb, const SEXP px, const SEXP py) {
-    int n=length(px), m=length(lb), i, j, jj, *k, sk, pc=0;
+    int n=Rf_length(px), m=Rf_length(lb), i, j, jj, *k, sk, pc=0;
     double *x, ppx, ppy;
     SEXP res, px1, py1, lb1;
 
 	/*
-    PROTECT(px1 = MAYBE_REFERENCED(px) ? duplicate(px) : px); pc++;
-    PROTECT(py1 = MAYBE_REFERENCED(py) ? duplicate(py) : py); pc++;
-    PROTECT(lb1 = MAYBE_REFERENCED(lb) ? duplicate(lb) : lb); pc++;
+    PROTECT(px1 = MAYBE_REFERENCED(px) ? Rf_duplicate(px) : px); pc++;
+    PROTECT(py1 = MAYBE_REFERENCED(py) ? Rf_duplicate(py) : py); pc++;
+    PROTECT(lb1 = MAYBE_REFERENCED(lb) ? Rf_duplicate(lb) : lb); pc++;
 	*/
 	if (MAYBE_REFERENCED(px)) {
-		PROTECT(px1 = duplicate(px));
+		PROTECT(px1 = Rf_duplicate(px));
 		pc++;
 	} else
 		px1 = px;
 	if (MAYBE_REFERENCED(py)) {
-		PROTECT(py1 = duplicate(py));
+		PROTECT(py1 = Rf_duplicate(py));
 		pc++;
 	} else
 		py1 = py;
 	if (MAYBE_REFERENCED(lb)) {
-		PROTECT(lb1 = duplicate(lb));
+		PROTECT(lb1 = Rf_duplicate(lb));
 		pc++;
 	} else
 		lb1 = lb;
diff --git a/src/sp.h b/src/sp.h
index 9cf0ede..0739877 100644
--- a/src/sp.h
+++ b/src/sp.h
@@ -1,14 +1,9 @@
 #ifndef R_SP_H
 #define R_SP_H
 
-#ifdef SP_XPORT
-# define SP_PREFIX(name) SP_XPORT(name)
-#else
-# define SP_PREFIX(name) name
+#ifndef R_NO_REMAP
+# define R_NO_REMAP
 #endif
-/* remember to touch local_stubs.c */
-
-#define SP_VERSION "2.1-4"
 
 #include <R.h>
 /* RSB 091203 */
@@ -52,47 +47,46 @@ typedef struct polygon {
 
 void setup_poly_minmax(POLYGON *pl);
 char InPoly(PLOT_POINT q, POLYGON *Poly);
-SEXP R_point_in_polygon_sp(SEXP px, SEXP py, SEXP polx, SEXP poly);
+SEXP R_point_in_polygon_sp(SEXP px, SEXP py, SEXP polx, SEXP poly); /* point.in.polygon.R */
 void sarea(double *heights, int *nx, int *ny, double *w, double *h, 
-	double *sa, int *bycell);
+	double *sa, int *bycell); /* surfaceArea.R */
 void spRFindCG( int *n, double *x, double *y, double *xc, double *yc, 
-		double *area );
+		double *area ); /* SpatialPolygons-internals.R */
 void sp_gcdist(double *lon1, double *lon2, double *lat1, double *lat2, 
 		double *dist);
 void sp_dists(double *u, double *v, double *uout, double *vout, 
-		int *n, double *dists, int *lonlat);
+		int *n, double *dists, int *lonlat); /* spdists.R */
 void sp_dists_NN(double *u1, double *v1, double *u2, double *v2,
-        int *n, double *dists, int *lonlat);
-void sp_lengths(double *u, double *v, int *n, double *lengths, int *lonlat);
-SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP sp_duplicates(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP pointsInBox(SEXP lb, SEXP px, SEXP py);
-SEXP tList(SEXP nl, SEXP m);
+        int *n, double *dists, int *lonlat); /* spdists.R */
+void sp_lengths(double *u, double *v, int *n, double *lengths, int *lonlat); /* SpatialLines-methods.R */
+SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp); /* zerodist.R */
+SEXP sp_duplicates(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp); /* zerodist.R */
+SEXP pointsInBox(SEXP lb, SEXP px, SEXP py); /* point.in.polygon.R */
+SEXP tList(SEXP nl, SEXP m); /* point.in.polygon.R */
 
 /* RSB 091203 */
 
 #define DIM     2               /* Dimension of points */
 typedef double  tPointd[DIM];   /* type double point */
 
-double  SP_PREFIX(Area2)(const tPointd a, const tPointd b, const tPointd c);
-void    SP_PREFIX(FindCG)(int n, tPointd *P, tPointd CG, double *Areasum2);
-void    SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, 
+double  Area2(const tPointd a, const tPointd b, const tPointd c);
+void    FindCG(int n, tPointd *P, tPointd CG, double *Areasum2);
+void    Centroid3(const tPointd p1, const tPointd p2, 
 	const tPointd p3, tPointd c);
-void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords, 
+void spRFindCG_c(const SEXP n, const SEXP coords, 
 	double *xc, double *yc, double *area );
-void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps);
-
-SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP hole);
-SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID);
-SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO, const SEXP p4s);
-SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls);
-SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_getIDs_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls);
-SEXP SP_PREFIX(comment2comm)(const SEXP obj);
-SEXP SP_PREFIX(sp_linkingTo_version)(void);
+void comm2comment(char *buf, int bufsiz, int *comm, int nps);
+
+SEXP Polygon_c(const SEXP coords, const SEXP n, const SEXP hole); /* SpatialPolygons-methods.R */
+SEXP Polygons_c(const SEXP pls, const SEXP ID); /* SpatialPolygons-methods.R */
+SEXP SpatialPolygons_c(const SEXP pls, const SEXP pO, const SEXP p4s); /* SpatialPolygons-methods.R */
+SEXP bboxCalcR_c(const SEXP pls); /* SpatialPolygonsDataFrame-methods.R */
+SEXP Polygon_validate_c(const SEXP obj); /* Class-SpatialPolygons.R */
+SEXP Polygons_validate_c(const SEXP obj); /* Class-SpatialPolygons.R */
+SEXP SpatialPolygons_validate_c(const SEXP obj); /* Class-SpatialPolygons.R */
+SEXP SpatialPolygons_getIDs_c(const SEXP obj); /* chfids.R Class-SpatialPolygons.R SpatialPolygonsDataFrame-methods.R */
+SEXP SpatialPolygons_plotOrder_c(const SEXP pls); /* SpatialPolygonsDataFrame-methods.R SpatialPolygons-methods.R */
+SEXP comment2comm(const SEXP obj);
+// SEXP sp_linkingTo_version(void);
 #endif
-/* remember to touch local_stubs.c */
 
diff --git a/src/sp.h.in b/src/sp.h.in
deleted file mode 100644
index dce352e..0000000
--- a/src/sp.h.in
+++ /dev/null
@@ -1,98 +0,0 @@
-#ifndef R_SP_H
-#define R_SP_H
-
-#ifdef SP_XPORT
-# define SP_PREFIX(name) SP_XPORT(name)
-#else
-# define SP_PREFIX(name) name
-#endif
-/* remember to touch local_stubs.c */
-
-#define SP_VERSION "@VERSION@"
-
-#include <R.h>
-/* RSB 091203 */
-#include <Rdefines.h>
-#define R_OFFSET 1
-#include <Rinternals.h>
-#include <Rmath.h>
-
-/* from insiders.c 
-
-int pipbb(double pt1, double pt2, double *bbs);
-int between(double x, double low, double up); 
-SEXP insiders(SEXP n1, SEXP bbs); */
-
-/* from pip.c */
-
-#ifndef MIN
-# define MIN(a,b) ((a)>(b)?(b):(a))
-#endif
-#ifndef MAX
-# define MAX(a,b) ((a)>(b)?(a):(b))
-#endif
-
-#define BUFSIZE 8192
-
-/* polygon structs: */
-typedef struct {
-	double		x, y;
-} PLOT_POINT;
-
-typedef struct {
-	PLOT_POINT	min, max;
-} MBR;
-
-typedef struct polygon {
-	MBR mbr;
-	int lines;
-	PLOT_POINT	*p;
-    int close; /* 1 - is closed polygon */
-} POLYGON;
-
-void setup_poly_minmax(POLYGON *pl);
-char InPoly(PLOT_POINT q, POLYGON *Poly);
-SEXP R_point_in_polygon_sp(SEXP px, SEXP py, SEXP polx, SEXP poly);
-void sarea(double *heights, int *nx, int *ny, double *w, double *h, 
-	double *sa, int *bycell);
-void spRFindCG( int *n, double *x, double *y, double *xc, double *yc, 
-		double *area );
-void sp_gcdist(double *lon1, double *lon2, double *lat1, double *lat2, 
-		double *dist);
-void sp_dists(double *u, double *v, double *uout, double *vout, 
-		int *n, double *dists, int *lonlat);
-void sp_dists_NN(double *u1, double *v1, double *u2, double *v2,
-        int *n, double *dists, int *lonlat);
-void sp_lengths(double *u, double *v, int *n, double *lengths, int *lonlat);
-SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP sp_duplicates(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp);
-SEXP pointsInBox(SEXP lb, SEXP px, SEXP py);
-SEXP tList(SEXP nl, SEXP m);
-
-/* RSB 091203 */
-
-#define DIM     2               /* Dimension of points */
-typedef double  tPointd[DIM];   /* type double point */
-
-double  SP_PREFIX(Area2)(const tPointd a, const tPointd b, const tPointd c);
-void    SP_PREFIX(FindCG)(int n, tPointd *P, tPointd CG, double *Areasum2);
-void    SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, 
-	const tPointd p3, tPointd c);
-void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords, 
-	double *xc, double *yc, double *area );
-void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps);
-
-SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP hole);
-SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID);
-SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO, const SEXP p4s);
-SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls);
-SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_getIDs_c)(const SEXP obj);
-SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls);
-SEXP SP_PREFIX(comment2comm)(const SEXP obj);
-SEXP SP_PREFIX(sp_linkingTo_version)(void);
-#endif
-/* remember to touch local_stubs.c */
-
diff --git a/src/sp_xports.c b/src/sp_xports.c
index 0155287..ad228e7 100644
--- a/src/sp_xports.c
+++ b/src/sp_xports.c
@@ -3,16 +3,16 @@
 #include "sp.h"
 /* remember to touch local_stubs.c */
 
-SEXP SP_PREFIX(sp_linkingTo_version)(void) {
+/* SEXP sp_linkingTo_version(void) {
     SEXP ans;
     PROTECT(ans = NEW_CHARACTER(1));
     SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING(SP_VERSION));
+           Rf_mkChar(SP_VERSION));
     UNPROTECT(1);
     return(ans);
-}
+} */
 
-SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
+SEXP Polygon_c(const SEXP coords, const SEXP n, const SEXP ihole) {
 
     SEXP SPans, labpt, Area, ringDir, hole, cls;
     double area, xc, yc;
@@ -25,9 +25,9 @@ SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
 
     for (i=0; i<nn; i++) {
        if(!R_FINITE(NUMERIC_POINTER(coords)[i]))
-           error("non-finite x coordinate");
+           Rf_error("non-finite x coordinate");
        if(!R_FINITE(NUMERIC_POINTER(coords)[i+nn]))
-           error("non-finite y coordinate");
+           Rf_error("non-finite y coordinate");
     }
 
 // 140406 ring closure
@@ -44,10 +44,10 @@ SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
         nn++;
         INTEGER_POINTER(dim1)[0] = nn;
         INTEGER_POINTER(dim1)[1] = 2;
-        setAttrib(ccopy, R_DimSymbol, dim1);
+        Rf_setAttrib(ccopy, R_DimSymbol, dim1);
     } else {
 		if (MAYBE_REFERENCED(coords)) {
-			PROTECT(ccopy = duplicate(coords)); 
+			PROTECT(ccopy = Rf_duplicate(coords)); 
 			pc++;
 		} else 
 			ccopy = coords; 
@@ -55,8 +55,8 @@ SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
 
 	/* from here one, ccopy is closed, and can be modified */
 
-    /* SP_PREFIX(spRFindCG_c)(n, ccopy, &xc, &yc, &area); */
-    SP_PREFIX(spRFindCG_c)(getAttrib(ccopy, R_DimSymbol), ccopy, &xc, &yc, &area);
+    /* spRFindCG_c(n, ccopy, &xc, &yc, &area); */
+    spRFindCG_c(Rf_getAttrib(ccopy, R_DimSymbol), ccopy, &xc, &yc, &area);
     if (fabs(area) < DBL_EPSILON) {
         if (!R_FINITE(xc) || !R_FINITE(yc)) {
             if (nn == 1) {
@@ -119,58 +119,58 @@ SEXP SP_PREFIX(Polygon_c)(const SEXP coords, const SEXP n, const SEXP ihole) {
        }
     }
 
-    SET_SLOT(SPans, install("coords"), ccopy);
+    SET_SLOT(SPans, Rf_install("coords"), ccopy);
 
     PROTECT(labpt = NEW_NUMERIC(2)); pc++;
     NUMERIC_POINTER(labpt)[0] = xc;
     NUMERIC_POINTER(labpt)[1] = yc;
-    SET_SLOT(SPans, install("labpt"), labpt);
+    SET_SLOT(SPans, Rf_install("labpt"), labpt);
 
     PROTECT(Area = NEW_NUMERIC(1)); pc++;
     NUMERIC_POINTER(Area)[0] = fabs(area);
-    SET_SLOT(SPans, install("area"), Area);
+    SET_SLOT(SPans, Rf_install("area"), Area);
 
-    SET_SLOT(SPans, install("hole"), hole);
-    SET_SLOT(SPans, install("ringDir"), ringDir);
+    SET_SLOT(SPans, Rf_install("hole"), hole);
+    SET_SLOT(SPans, Rf_install("ringDir"), ringDir);
 
-    PROTECT(valid = SP_PREFIX(Polygon_validate_c)(SPans)); pc++;
+    PROTECT(valid = Polygon_validate_c(SPans)); pc++;
 
-    if (! isLogical(valid)) {
+    if (! Rf_isLogical(valid)) {
         UNPROTECT(pc);
 		/*
         if (isString(valid)) 
-			error(CHAR(STRING_ELT(valid, 0)));
+			Rf_error(CHAR(STRING_ELT(valid, 0)));
         else 
 		*/
-			error("invalid Polygon object");
+			Rf_error("invalid Polygon object");
     }
 
     UNPROTECT(pc);
     return(SPans);
 }
 
-SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj) {
+SEXP Polygon_validate_c(const SEXP obj) {
 
     int pc=0;
     int n;
     SEXP coords, labpt, ans;
 
-    coords = GET_SLOT(obj, install("coords"));
-    n = INTEGER_POINTER(getAttrib(coords, R_DimSymbol))[0];
+    coords = GET_SLOT(obj, Rf_install("coords"));
+    n = INTEGER_POINTER(Rf_getAttrib(coords, R_DimSymbol))[0];
     if (NUMERIC_POINTER(coords)[0] != NUMERIC_POINTER(coords)[n-1]
         || NUMERIC_POINTER(coords)[n] != NUMERIC_POINTER(coords)[(2*n)-1]) {
        PROTECT(ans = NEW_CHARACTER(1)); pc++;
        SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("ring not closed"));
+           Rf_mkChar("ring not closed"));
        UNPROTECT(pc);
        return(ans);
     }
-    labpt = GET_SLOT(obj, install("labpt"));
+    labpt = GET_SLOT(obj, Rf_install("labpt"));
     if (!R_FINITE(NUMERIC_POINTER(labpt)[0]) ||
         !R_FINITE(NUMERIC_POINTER(labpt)[1])) {
         PROTECT(ans = NEW_CHARACTER(1)); pc++;
         SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("infinite label point"));
+           Rf_mkChar("infinite label point"));
        UNPROTECT(pc);
        return(ans);
     }
@@ -180,7 +180,7 @@ SEXP SP_PREFIX(Polygon_validate_c)(const SEXP obj) {
     return(ans);
 }
 
-SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
+SEXP Polygons_c(const SEXP pls, const SEXP ID) {
 
     SEXP ans, labpt, Area, plotOrder, crds, pl, n, hole, pls1, ID1, cls;
     int nps, i, pc=0, sumholes;
@@ -189,19 +189,19 @@ SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
     SEXP valid;
 
 	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls)); 
+		PROTECT(pls1 = Rf_duplicate(pls)); 
 		pc++;
 	} else 
 		pls1 = pls; 
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
+    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? Rf_duplicate(pls) : pls); pc++;
 	if (MAYBE_REFERENCED(ID)) {
-		PROTECT(ID1 = duplicate(ID)); 
+		PROTECT(ID1 = Rf_duplicate(ID)); 
 		pc++;
 	} else 
 		ID1 = ID; 
-    // PROTECT(ID1 = MAYBE_REFERENCED(ID) ? duplicate(ID) : ID); pc++;
+    // PROTECT(ID1 = MAYBE_REFERENCED(ID) ? Rf_duplicate(ID) : ID); pc++;
 
-    nps = length(pls1);
+    nps = Rf_length(pls1);
     fuzz = R_pow(DBL_EPSILON, (2.0/3.0));
     areas = (double *) R_alloc((size_t) nps, sizeof(double));
     areaseps = (double *) R_alloc((size_t) nps, sizeof(double));
@@ -209,9 +209,9 @@ SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
 
     for (i=0, sumholes=0; i<nps; i++) {
         areas[i] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("area")))[0]; 
+            Rf_install("area")))[0]; 
         holes[i] = LOGICAL_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("hole")))[0];
+            Rf_install("hole")))[0];
          areaseps[i] = holes[i] ? areas[i] + fuzz : areas[i];
          sumholes += holes[i];
     }
@@ -225,13 +225,13 @@ SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
 
     if (sumholes == nps) {
         crds = GET_SLOT(VECTOR_ELT(pls1, (po[0] - R_OFFSET)),
-            install("coords"));
+            Rf_install("coords"));
         PROTECT(n = NEW_INTEGER(1)); pc++;
-        INTEGER_POINTER(n)[0] = INTEGER_POINTER(getAttrib(crds,
+        INTEGER_POINTER(n)[0] = INTEGER_POINTER(Rf_getAttrib(crds,
             R_DimSymbol))[0];
         PROTECT(hole = NEW_LOGICAL(1)); pc++;
         LOGICAL_POINTER(hole)[0] = FALSE;
-        pl = SP_PREFIX(Polygon_c)(crds, n, hole);
+        pl = Polygon_c(crds, n, hole);
 /* bug 100417 Patrick Giraudoux */
         holes[po[0] - R_OFFSET] = LOGICAL_POINTER(hole)[0];
         SET_VECTOR_ELT(pls1, (po[0] - R_OFFSET), pl);
@@ -240,78 +240,78 @@ SEXP SP_PREFIX(Polygons_c)(const SEXP pls, const SEXP ID) {
 // rchk MAKE_CLASS allocates RSB 180602
     PROTECT(cls = MAKE_CLASS("Polygons")); pc++;
     PROTECT(ans = NEW_OBJECT(cls)); pc++;
-    SET_SLOT(ans, install("Polygons"), pls1);
-    SET_SLOT(ans, install("ID"), ID1);
+    SET_SLOT(ans, Rf_install("Polygons"), pls1);
+    SET_SLOT(ans, Rf_install("ID"), ID1);
 
     PROTECT(Area = NEW_NUMERIC(1)); pc++;
     NUMERIC_POINTER(Area)[0] = 0.0;
     for (i=0; i<nps; i++)
         NUMERIC_POINTER(Area)[0] += holes[i] ? 0.0 : fabs(areas[i]);
 
-    SET_SLOT(ans, install("area"), Area);
+    SET_SLOT(ans, Rf_install("area"), Area);
 
     PROTECT(plotOrder = NEW_INTEGER(nps)); pc++;
     for (i=0; i<nps; i++)
 		INTEGER_POINTER(plotOrder)[i] = po[i];
 
-    SET_SLOT(ans, install("plotOrder"), plotOrder);
+    SET_SLOT(ans, Rf_install("plotOrder"), plotOrder);
 
     PROTECT(labpt = NEW_NUMERIC(2)); pc++;
     NUMERIC_POINTER(labpt)[0] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1,
-        (po[0]-1)), install("labpt")))[0];
+        (po[0]-1)), Rf_install("labpt")))[0];
     NUMERIC_POINTER(labpt)[1] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1,
-        (po[0]-1)), install("labpt")))[1];
-    SET_SLOT(ans, install("labpt"), labpt);
+        (po[0]-1)), Rf_install("labpt")))[1];
+    SET_SLOT(ans, Rf_install("labpt"), labpt);
 
-    PROTECT(valid = SP_PREFIX(Polygons_validate_c)(ans)); pc++;
-    if (!isLogical(valid)) {
+    PROTECT(valid = Polygons_validate_c(ans)); pc++;
+    if (!Rf_isLogical(valid)) {
         UNPROTECT(pc);
 		/*
         if (isString(valid)) 
-			error(CHAR(STRING_ELT(valid, 0)));
+			Rf_error(CHAR(STRING_ELT(valid, 0)));
         else
 		*/
-			error("invalid Polygons object");
+			Rf_error("invalid Polygons object");
     }
 
     UNPROTECT(pc);
     return(ans);
 }
 
-SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj) {
+SEXP Polygons_validate_c(const SEXP obj) {
 
     int pc=0;
     int i, n;
     SEXP Pls, labpt, ans;
     char *cls="Polygon";
 
-    PROTECT(Pls = GET_SLOT(obj, install("Polygons"))); pc++;
-    n = length(Pls);
+    PROTECT(Pls = GET_SLOT(obj, Rf_install("Polygons"))); pc++;
+    n = Rf_length(Pls);
     for (i=0; i<n; i++) {
-        if (strcmp(CHAR(STRING_ELT(getAttrib(VECTOR_ELT(Pls, i),
+        if (strcmp(CHAR(STRING_ELT(Rf_getAttrib(VECTOR_ELT(Pls, i),
            R_ClassSymbol), 0)), cls) != 0) {
               PROTECT(ans = NEW_CHARACTER(1)); pc++;
               SET_STRING_ELT(ans, 0,
-              COPY_TO_USER_STRING("Polygons slot contains non-Polygon object"));
+              Rf_mkChar("Polygons slot contains non-Polygon object"));
               UNPROTECT(pc);
               return(ans);
         }
     }
 
-    if (n != length(GET_SLOT(obj, install("plotOrder")))) {
+    if (n != Rf_length(GET_SLOT(obj, Rf_install("plotOrder")))) {
         PROTECT(ans = NEW_CHARACTER(1)); pc++;
         SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("plotOrder and Polygons differ in length"));
+           Rf_mkChar("plotOrder and Polygons differ in length"));
         UNPROTECT(pc);
         return(ans);
     }
 
-    labpt = GET_SLOT(obj, install("labpt"));
+    labpt = GET_SLOT(obj, Rf_install("labpt"));
     if (!R_FINITE(NUMERIC_POINTER(labpt)[0]) ||
       !R_FINITE(NUMERIC_POINTER(labpt)[1])) {
       PROTECT(ans = NEW_CHARACTER(1)); pc++;
       SET_STRING_ELT(ans, 0,
-         COPY_TO_USER_STRING("infinite label point"));
+         Rf_mkChar("infinite label point"));
       UNPROTECT(pc);
       return(ans);
     }
@@ -322,7 +322,7 @@ SEXP SP_PREFIX(Polygons_validate_c)(const SEXP obj) {
 
 }
 
-SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO, 
+SEXP SpatialPolygons_c(const SEXP pls, const SEXP pO, 
 		const SEXP p4s) {
 
     SEXP ans, bbox, ppO, cls;
@@ -331,47 +331,47 @@ SEXP SP_PREFIX(SpatialPolygons_c)(const SEXP pls, const SEXP pO,
 // rchk MAKE_CLASS allocates RSB 180602
     PROTECT(cls = MAKE_CLASS("SpatialPolygons")); pc++;
     PROTECT(ans = NEW_OBJECT(cls)); pc++;
-    // SET_SLOT(ans, install("polygons"), MAYBE_REFERENCED(pls) ? duplicate(pls) : pls);
-    SET_SLOT(ans, install("polygons"), pls);
-    // SET_SLOT(ans, install("proj4string"), MAYBE_REFERENCED(p4s) ? duplicate(p4s) : p4s);
-    SET_SLOT(ans, install("proj4string"), p4s);
+    // SET_SLOT(ans, Rf_install("polygons"), MAYBE_REFERENCED(pls) ? Rf_duplicate(pls) : pls);
+    SET_SLOT(ans, Rf_install("polygons"), pls);
+    // SET_SLOT(ans, Rf_install("proj4string"), MAYBE_REFERENCED(p4s) ? Rf_duplicate(p4s) : p4s);
+    SET_SLOT(ans, Rf_install("proj4string"), p4s);
 
     if (pO == R_NilValue) {
-		PROTECT(ppO = SP_PREFIX(SpatialPolygons_plotOrder_c)(pls));
+		PROTECT(ppO = SpatialPolygons_plotOrder_c(pls));
 		pc++;
     } else
 		ppO = pO;
-    // SET_SLOT(ans, install("plotOrder"), MAYBE_REFERENCED(pO) ? duplicate(pO) : pO);
-    SET_SLOT(ans, install("plotOrder"), ppO);
+    // SET_SLOT(ans, Rf_install("plotOrder"), MAYBE_REFERENCED(pO) ? Rf_duplicate(pO) : pO);
+    SET_SLOT(ans, Rf_install("plotOrder"), ppO);
 
-    PROTECT(bbox = SP_PREFIX(bboxCalcR_c(pls))); pc++;
-    SET_SLOT(ans, install("bbox"), bbox);
+    PROTECT(bbox = bboxCalcR_c(pls)); pc++;
+    SET_SLOT(ans, Rf_install("bbox"), bbox);
 
     UNPROTECT(pc);
     return(ans);
 
 }
 
-SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls) {
+SEXP SpatialPolygons_plotOrder_c(const SEXP pls) {
 
     SEXP plotOrder, pls1;
     int pc=0, ng, i;
     int *po;
     double *areas;
 
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
+    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? Rf_duplicate(pls) : pls); pc++;
 	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls));
+		PROTECT(pls1 = Rf_duplicate(pls));
 		pc++;
 	} else
 		pls1 = pls;
 
-    ng = length(pls1);
+    ng = Rf_length(pls1);
     areas = (double *) R_alloc((size_t) ng, sizeof(double));
     po = (int *) R_alloc((size_t) ng, sizeof(int));
     for (i=0; i<ng; i++) {
         areas[i] = NUMERIC_POINTER(GET_SLOT(VECTOR_ELT(pls1, i),
-            install("area")))[0]; 
+            Rf_install("area")))[0]; 
         po[i] = i + R_OFFSET;
     }
     revsort(areas, po, ng);
@@ -384,30 +384,30 @@ SEXP SP_PREFIX(SpatialPolygons_plotOrder_c)(const SEXP pls) {
 
 }
 
-SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj) {
+SEXP SpatialPolygons_validate_c(const SEXP obj) {
 
     int pc=0;
     int i, n;
     SEXP pls, ans;
     char *cls="Polygons";
 
-    PROTECT(pls = GET_SLOT(obj, install("polygons"))); pc++;
-    n = length(pls);
+    PROTECT(pls = GET_SLOT(obj, Rf_install("polygons"))); pc++;
+    n = Rf_length(pls);
     for (i=0; i<n; i++) {
-        if (strcmp(CHAR(STRING_ELT(getAttrib(VECTOR_ELT(pls, i),
+        if (strcmp(CHAR(STRING_ELT(Rf_getAttrib(VECTOR_ELT(pls, i),
            R_ClassSymbol), 0)), cls) != 0) {
              PROTECT(ans = NEW_CHARACTER(1)); pc++;
              SET_STRING_ELT(ans, 0,
-             COPY_TO_USER_STRING("polygons slot contains non-Polygons object"));
+             Rf_mkChar("polygons slot contains non-Polygons object"));
              UNPROTECT(pc);
              return(ans);
         }
     }
 
-    if (n != length(GET_SLOT(obj, install("plotOrder")))) {
+    if (n != Rf_length(GET_SLOT(obj, Rf_install("plotOrder")))) {
         PROTECT(ans = NEW_CHARACTER(1)); pc++;
         SET_STRING_ELT(ans, 0,
-           COPY_TO_USER_STRING("plotOrder and polygons differ in length"));
+           Rf_mkChar("plotOrder and polygons differ in length"));
         UNPROTECT(pc);
         return(ans);
     }
@@ -419,55 +419,55 @@ SEXP SP_PREFIX(SpatialPolygons_validate_c)(const SEXP obj) {
 
 }
 
-SEXP SP_PREFIX(SpatialPolygons_getIDs_c)(const SEXP obj) {
+SEXP SpatialPolygons_getIDs_c(const SEXP obj) {
 
     int pc=0;
     int i, n;
     SEXP pls, IDs, obj1;
 
-    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? duplicate(obj) : obj); pc++;
+    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? Rf_duplicate(obj) : obj); pc++;
 	if (MAYBE_REFERENCED(obj)) {
-		PROTECT(obj1 = duplicate(obj));
+		PROTECT(obj1 = Rf_duplicate(obj));
 		pc++;
 	} else
 		obj1 = obj;
 
-    PROTECT(pls = GET_SLOT(obj, install("polygons"))); pc++;
-    n = length(pls);
+    PROTECT(pls = GET_SLOT(obj, Rf_install("polygons"))); pc++;
+    n = Rf_length(pls);
     PROTECT(IDs = NEW_CHARACTER(n)); pc++;
     for (i=0; i<n; i++)
         SET_STRING_ELT(IDs, i, STRING_ELT(GET_SLOT(VECTOR_ELT(pls, i),
-            install("ID")), 0));
+            Rf_install("ID")), 0));
       
     UNPROTECT(pc);
     return(IDs);
 
 }
 
-SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls) {
+SEXP bboxCalcR_c(const SEXP pls) {
 
     SEXP ans, dim, dimnames, Pl, crds, pls1;
     double UX=-DBL_MAX, LX=DBL_MAX, UY=-DBL_MAX, LY=DBL_MAX;
     int i, j, k, n, npls, npl, pc=0;
     double x, y;
 
-    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? duplicate(pls) : pls); pc++;
+    // PROTECT(pls1 = MAYBE_REFERENCED(pls) ? Rf_duplicate(pls) : pls); pc++;
 	if (MAYBE_REFERENCED(pls)) {
-		PROTECT(pls1 = duplicate(pls));
+		PROTECT(pls1 = Rf_duplicate(pls));
 		pc++;
 	} else
 		pls1 = pls;
 
-    npls = length(pls1);
+    npls = Rf_length(pls1);
 	if (npls == 0) { /* EJP: this makes a zero-length object at least pass further sanity checks */
 		UX = UY = DBL_MAX;
 		LX = LY = -DBL_MAX;
 	} else for (i=0; i<npls; i++) {
-        Pl = GET_SLOT(VECTOR_ELT(pls1, i), install("Polygons"));
-        npl = length(Pl);
+        Pl = GET_SLOT(VECTOR_ELT(pls1, i), Rf_install("Polygons"));
+        npl = Rf_length(Pl);
         for (j=0; j<npl; j++) {
-            crds = GET_SLOT(VECTOR_ELT(Pl, j), install("coords"));
-            n = INTEGER_POINTER(getAttrib(crds, R_DimSymbol))[0];
+            crds = GET_SLOT(VECTOR_ELT(Pl, j), Rf_install("coords"));
+            n = INTEGER_POINTER(Rf_getAttrib(crds, R_DimSymbol))[0];
             for (k=0; k<n; k++) {
                x = NUMERIC_POINTER(crds)[k];
                y = NUMERIC_POINTER(crds)[k+n];
@@ -487,21 +487,21 @@ SEXP SP_PREFIX(bboxCalcR_c)(const SEXP pls) {
     PROTECT(dim = NEW_INTEGER(2)); pc++;
     INTEGER_POINTER(dim)[0] = 2;
     INTEGER_POINTER(dim)[1] = 2;
-    setAttrib(ans, R_DimSymbol, dim);
+    Rf_setAttrib(ans, R_DimSymbol, dim);
     PROTECT(dimnames = NEW_LIST(2)); pc++;
     SET_VECTOR_ELT(dimnames, 0, NEW_CHARACTER(2));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 0, COPY_TO_USER_STRING("x"));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 1, COPY_TO_USER_STRING("y"));
+    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 0, Rf_mkChar("x"));
+    SET_STRING_ELT(VECTOR_ELT(dimnames, 0), 1, Rf_mkChar("y"));
     SET_VECTOR_ELT(dimnames, 1, NEW_CHARACTER(2));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 0, COPY_TO_USER_STRING("min"));
-    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 1, COPY_TO_USER_STRING("max"));
-    setAttrib(ans, R_DimNamesSymbol, dimnames);
+    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 0, Rf_mkChar("min"));
+    SET_STRING_ELT(VECTOR_ELT(dimnames, 1), 1, Rf_mkChar("max"));
+    Rf_setAttrib(ans, R_DimNamesSymbol, dimnames);
     UNPROTECT(pc);
     return(ans);
 
 }
 
-void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords, 
+void spRFindCG_c(const SEXP n, const SEXP coords, 
 		double *xc, double *yc, double *area ) {
 
 	int i, nn;
@@ -515,14 +515,14 @@ void SP_PREFIX(spRFindCG_c)(const SEXP n, const SEXP coords,
 		P[i][0] = NUMERIC_POINTER(coords)[i];
 		P[i][1] = NUMERIC_POINTER(coords)[i+nn];
 	}
-	SP_PREFIX(FindCG)(nn, P, CG, &Areasum2);
+	FindCG(nn, P, CG, &Areasum2);
 	xc[0] = CG[0];
 	yc[0] = CG[1];
 	area[0] = Areasum2/2;
 	return;
 }
 
-void SP_PREFIX(FindCG)( int n, tPointd *P, tPointd CG, double *Areasum2) {
+void FindCG( int n, tPointd *P, tPointd CG, double *Areasum2) {
 	int     i;
 	double  A2;        /* Partial area sum */    
 	tPointd Cent3;
@@ -531,8 +531,8 @@ void SP_PREFIX(FindCG)( int n, tPointd *P, tPointd CG, double *Areasum2) {
 	CG[1] = 0;
 	Areasum2[0] = 0;
 	for (i = 1; i < n-1; i++) {
-		SP_PREFIX(Centroid3)( P[0], P[i], P[i+1], Cent3 );
-		A2 =  SP_PREFIX(Area2)( P[0], P[i], P[i+1]);
+		Centroid3( P[0], P[i], P[i+1], Cent3 );
+		A2 =  Area2( P[0], P[i], P[i+1]);
 		CG[0] += A2 * Cent3[0];
 		CG[1] += A2 * Cent3[1];
 		Areasum2[0] += A2;
@@ -545,7 +545,7 @@ void SP_PREFIX(FindCG)( int n, tPointd *P, tPointd CG, double *Areasum2) {
 	Returns three times the centroid.  The factor of 3 is
 	left in to permit division to be avoided until later.
 */
-void SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, const tPointd p3, 
+void Centroid3(const tPointd p1, const tPointd p2, const tPointd p3, 
 	tPointd c) {
         c[0] = p1[0] + p2[0] + p3[0];
         c[1] = p1[1] + p2[1] + p3[1];
@@ -555,34 +555,34 @@ void SP_PREFIX(Centroid3)(const tPointd p1, const tPointd p2, const tPointd p3,
         Returns twice the signed area of the triangle determined by a,b,c,
         positive if a,b,c are oriented ccw, and negative if cw.
 */
-double SP_PREFIX(Area2)(const tPointd a, const tPointd b, const tPointd c) {
+double Area2(const tPointd a, const tPointd b, const tPointd c) {
 	double area;
 	area = (b[0] - a[0]) * (c[1] - a[1]) - (c[0] - a[0]) * (b[1] - a[1]);
 	return(area);
 }
 
 
-SEXP SP_PREFIX(comment2comm)(const SEXP obj) {
+SEXP comment2comm(const SEXP obj) {
     SEXP ans, comment, obj1;
     int pc=0, ns, i, j, jj, k, nc;
     char s[15], *buf;
     int *c, *nss, *co, *coo;
 
-    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? duplicate(obj) : obj); pc++;
+    // PROTECT(obj1 = MAYBE_REFERENCED(obj) ? Rf_duplicate(obj) : obj); pc++;
 	if (MAYBE_REFERENCED(obj)) {
-		PROTECT(obj1 = duplicate(obj));
+		PROTECT(obj1 = Rf_duplicate(obj));
 		pc++;
 	} else
 		obj1 = obj;
 
-    PROTECT(comment = getAttrib(obj1, install("comment"))); pc++;
+    PROTECT(comment = Rf_getAttrib(obj1, Rf_install("comment"))); pc++;
     if (comment == R_NilValue) {
         UNPROTECT(pc);
         return(R_NilValue);
     }
 
-    nc = length(STRING_ELT(comment, 0));
-    if (nc < 1) error("comment2comm: empty string comment");
+    nc = Rf_length(STRING_ELT(comment, 0));
+    if (nc < 1) Rf_error("comment2comm: empty string comment");
 
     buf = (char *) R_alloc((size_t) (nc+1), sizeof(char));
 
@@ -610,14 +610,14 @@ SEXP SP_PREFIX(comment2comm)(const SEXP obj) {
     nss[(ns)] = k;
 
     s[0] = '\0';
-    if (nss[0] > 15) error("comment2comm: buffer overflow");
+    if (nss[0] > 15) Rf_error("comment2comm: buffer overflow");
     strncpy(s, &buf[0], (size_t) nss[0]);
     s[nss[0]] = '\0';
 
     c[0] = atoi(s);
     for (i=0; i<ns; i++) {
         k = nss[(i+1)]-(nss[i]+1);
-        if (k > 15) error("comment2comm: buffer overflow");
+        if (k > 15) Rf_error("comment2comm: buffer overflow");
         strncpy(s, &buf[(nss[i]+1)], (size_t) k);
         s[k] = '\0';
         c[i+1] = atoi(s);
@@ -653,20 +653,20 @@ SEXP SP_PREFIX(comment2comm)(const SEXP obj) {
     return(ans);
 }
 
-void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps) {
+void comm2comment(char *buf, int bufsiz, int *comm, int nps) {
     char cbuf[15];
     int i, nc, nc1, pr;
 
     nc = (int) (ceil(log10(nps)+1.0)+1.0);
     nc1 = (nc*nps)+1;
-    if (bufsiz < nc1) error("comm2comment: buffer overflow");
+    if (bufsiz < nc1) Rf_error("comm2comment: buffer overflow");
 
     pr = snprintf(buf, bufsiz, "%d", comm[0]);
     bufsiz -= pr;
     for (i = 1; i < nps; i++) {
         snprintf(cbuf, 15, " %d", comm[i]);
         if (strlen(cbuf) >= bufsiz)
-            error("comm2comment: buffer overflow");
+            Rf_error("comm2comment: buffer overflow");
         strncat(buf, cbuf, bufsiz);
         bufsiz -= strlen(cbuf);
     }
@@ -674,4 +674,4 @@ void SP_PREFIX(comm2comment)(char *buf, int bufsiz, int *comm, int nps) {
     return;
 }
 
-/* remember to touch local_stubs.c */
+
diff --git a/src/zerodist.c b/src/zerodist.c
index a577c6e..0a4a317 100644
--- a/src/zerodist.c
+++ b/src/zerodist.c
@@ -34,12 +34,12 @@ SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp) {
 	ll = INTEGER_POINTER(lonlat)[0];
 	cmp = INTEGER_POINTER(mcmp)[0];
 	if (ll && ncol != 2)
-		error("for longlat data, coordinates should be two-dimensional");
+		Rf_error("for longlat data, coordinates should be two-dimensional");
 	nrow = LENGTH(pp)/ncol;
 	zerodist2 = NUMERIC_POINTER(zero)[0] * NUMERIC_POINTER(zero)[0];
 	x = (double **) malloc((size_t) nrow * sizeof(double *));
 	if (x == NULL)
-		error("could not allocate vector of %lu bytes in zerodist",
+		Rf_error("could not allocate vector of %lu bytes in zerodist",
 			(long unsigned int) (nrow * sizeof(double *)));
 	for (i = 0; i < nrow; i++)
 		x[i] = &(NUMERIC_POINTER(pp)[i*ncol]);
@@ -49,7 +49,7 @@ SEXP sp_zerodist(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp) {
 			if (is_zero(x[i], x[j], ncol, ll, zerodist2, cmp)) {
 				which = (unsigned int *) realloc(which, (size_t) (nzero+2) * sizeof(unsigned int));
 				if (which == NULL)
-					error("could not allocate vector of %u bytes in zerodist",
+					Rf_error("could not allocate vector of %u bytes in zerodist",
 						nzero + 2);
 				which[nzero] = j; /* lowest */
 				which[nzero + 1] = i;
@@ -77,12 +77,12 @@ SEXP sp_duplicates(SEXP pp, SEXP pncol, SEXP zero, SEXP lonlat, SEXP mcmp) {
 	ll = INTEGER_POINTER(lonlat)[0];
 	cmp = INTEGER_POINTER(mcmp)[0];
 	if (ll && ncol != 2)
-		error("for longlat data, coordinates should be two-dimensional");
+		Rf_error("for longlat data, coordinates should be two-dimensional");
 	nrow = LENGTH(pp)/ncol;
 	zerodist2 = NUMERIC_POINTER(zero)[0] * NUMERIC_POINTER(zero)[0];
 	x = (double **) malloc((size_t) nrow * sizeof(double *));
 	if (x == NULL)
-		error("could not allocate vector of %lu bytes in zerodist",
+		Rf_error("could not allocate vector of %lu bytes in zerodist",
 			(long unsigned int) (nrow * sizeof(double *)));
 	for (i = 0; i < nrow; i++)
 		x[i] = &(NUMERIC_POINTER(pp)[i*ncol]);
diff --git a/vignettes/sp_gallery.Rmd b/vignettes/sp_gallery.Rmd
index 723828b..a97c52a 100644
--- a/vignettes/sp_gallery.Rmd
+++ b/vignettes/sp_gallery.Rmd
@@ -220,7 +220,7 @@ plot(geometry(meuse.grid), add = TRUE, col = grey(.8))
 ```
 
 Read
-[this](http://r-spatial.org/r/2016/03/08/plotting-spatial-grids.html)
+[this](https://r-spatial.org/r/2016/03/08/plotting-spatial-grids.html)
 blog post to find out more about the options available (and
 limitations) for plotting gridded data with base plot methods in sp.