Evil: Add evil_stdlib_mkstemp_create_many test case

[joaoantoniocardoso]

While investigating temporary file creation from evil I noticed that there are no tests to check if the implementation of mkstemp can create several files in sequence.

At the time I need to check that, than I wrote this simple test.

Maybe it worth to add in our current branch, what do you think?

[Coquinho]

Why 1000?

[joaoantoniocardoso]

First I thought to create as many files as possible, trying to reach the posix limit, but that is completely nonsense: it will take forever to finish, possibly reaching timeout.
Than I put some arbitrary quantity to be described as 'many'. 🙅

[Coquinho]

welp...probably there are few cases where people create as many as 1k temporary files, sooooo, fair enough

[joaoantoniocardoso]

Maybe it should be dynamically allocated?

[JPTIZ]

Also, any specific reason for unsigned long long in such a short value (1000)? If it is to conform with array length type, just use a straight forward size_t.

[JPTIZ]

Careful: this (declare without value to use inside one or multiple for-loops) is intensely error-prone (from accidental usage of unitialized value to accidental usage of an unexpected value that was given in a previous loop). I really would appreciate if it was used and declared in-loop:

Suggested change

	unsigned long long files_created;
	char templates[files_to_create][template_len];
	int fds[files_to_create] = { NULL };
	// Create temporary files
	for (files_created = 0; files_created < files_to_create; files_created++)
	{
	strncpy_s(templates[files_created], template_len, template, template_len);
	fds[files_created] = mkstemp(templates[files_created]);
	fail_if(fds[files_created] < 0);
	}
	// Close temporary files
	for (files_created = 0; files_created < files_to_create; files_created++)
	fail_if(close(fds[files_created]) == -1);
	// Remove temporary files
	for (files_created = 0; files_created < files_to_create; files_created++)
	fail_if(unlink(templates[files_created]) == -1);
	char templates[files_to_create][template_len];
	int fds[files_to_create] = { NULL };
	// Create temporary files
	for (size_t files_created = 0; files_created < files_to_create; files_created++)
	{
	strncpy_s(templates[files_created], template_len, template, template_len);
	fds[files_created] = mkstemp(templates[files_created]);
	fail_if(fds[files_created] < 0);
	}
	// Close temporary files
	for (size_t files_created = 0; files_created < files_to_create; files_created++)
	fail_if(close(fds[files_created]) == -1);
	// Remove temporary files
	for (size_t files_created = 0; files_created < files_to_create; files_created++)
	fail_if(unlink(templates[files_created]) == -1);

You don't have to worry about allocating multiple variables, since what will happen is that the compiler will reuse the same register for them, plus having additional guarantees over the expected variable initialization/value.