cwk_path_is_absolute returns an incorrect result

[kampeador]

Hello.
Thanks for your library and putting a lot of effort into it.

I've made this simple unit test and 5 asserts have failed.

#ifdef _WIN32
  const bool is_unix = false;
  cwk_path_set_style(CWK_STYLE_WINDOWS);
#else
  const bool is_posix = true;
  cwk_path_set_style(CWK_STYLE_UNIX);
#endif

  assert( cwk_path_is_absolute("/") == is_unix  ); // fails
  assert( cwk_path_is_absolute("/dir") == is_unix  ); // fails
  assert( cwk_path_is_absolute("/dir/") == is_unix  ); // fails
  assert( cwk_path_is_absolute("/dir/tmp") == is_unix  ); // fails
  assert( cwk_path_is_absolute("/dir/tmp/") == is_unix  ); // fails
  assert( ! cwk_path_is_absolute("dir") );
  assert( ! cwk_path_is_absolute("dir/") );
  assert( ! cwk_path_is_absolute("dir/tmp") );
  assert( ! cwk_path_is_absolute("dir/tmp/") );
  assert( ! cwk_path_is_absolute("c:") );
  assert( ! cwk_path_is_absolute("c:dir") );
  assert( ! cwk_path_is_absolute("c:dir/") );
  assert( ! cwk_path_is_absolute("c:dir/tmp") );
  assert( ! cwk_path_is_absolute("c:dir/tmp/") );
  assert( cwk_path_is_absolute("c:/") == !is_unix  );
  assert( cwk_path_is_absolute("c:/dir") == !is_unix  );
  assert( cwk_path_is_absolute("c:/dir/") == !is_unix  );
  assert( cwk_path_is_absolute("c:/dir/tmp") == !is_unix  );
  assert( cwk_path_is_absolute("c:/dir/tmp/") == !is_unix  );

Windows also has a PathIsRelativeA/W function, which can be used as reference. However it has some limitations e.g MAX_PATH limit.

[likle]

Hi @kampeador, thank you very much for your tests! I really appreciate it.

I believe the first five tests fail because cwalk consideres these to be absolute on windows too (please correct me if I am wrong).
PathIsRelative (shlwapi.h) does not seem to consider these to be absolute, and I am not sure why this is the case. The paths start with a slash, and usually that's considered to be equal with a backslash on most APIs. For instance, if you type cd / in a console it will bring you to the root of your current drive. Microsoft even has a few examples here, and the second one clearly shows that paths starting with a (back)slash should be absolute. I ran the following simple test based on those examples provided by Microsoft:

#include <Windows.h>
#include <shlwapi.h>
#include <stdio.h>

int main() {
  const char *paths[] = {
	"C:\\Documents\\Newsletters\\Summer2018.pdf",
	"\\Program Files\\Custom Utilities\\StringFinder.exe",
	"2018\\January.xlsx",
	"..\\Publications\\TravelBrochure.pdf",
	"C:Projects\\apilibrary\\apilibrary.sln",
	"C:\\Projects\\apilibrary\\apilibrary.sln"
  };

  for(int i = 0; i < sizeof(paths) / sizeof(*paths); ++i) {
	const char *result = PathIsRelativeA(paths[i]) ? "relative" : "absolute";
	printf("%s: %s\n", paths[i], result);
  }
}

which shows that C:Projects\apilibrary\apilibrary.sln is considered to be absolute by PathIsRelativeA which is probably not correct as Microsoft puts it:

A relative path from the current directory of the C: drive.

I'd be happy to change things but I am not sure what the reasoning behind this is, on my current knowledge it seems to me as if PathIsRelative is not always working as it should.

[kampeador]

I guess I've misunderstood terminology related to this library.
Absolute and relative paths have nothing to do in terms of comparison with shlwapi, C++17 filesystem, Qt etc.
They are related to the context of cwalk.
e.g. every cwk_path_get_absolute call must be validated with specific functions like GetFullPathNameW used to translate paths to specific context.

[likle]

I am not entirely sure whether I undestand you correctly. Could you elaborate on your example? Do you think we need to improve something in the documentation?

[kampeador]

For example: On Windows "absolute path" = "full path". "/", "/dir", "/dir/tmp" are considered relative in shlwapi, C++17 filesystem, Qt etc because there is an "Apply the current directory" translation stage.

From the link you've posted earlier:

If the path starts with a single component separator, the drive from the current directory is applied. For example, if the file path is \utilities and the current directory is C:\temp, normalization produces C:\utilities.

Drive can be changed dynamically using SetCurrentDirectoryW or _chdir functions.
cwalk is not aware of this global state and treats these relative paths as absolute. A potential solution could be using GetCurrentDirectoryW or _getcwd to supply this information for cwalk, but it will not work.

char buffer[FILENAME_MAX];
cwk_path_get_absolute("C:\temp\data", "\utilities", buffer, sizeof(buffer));
printf("buffer: %s\n", buffer);

will print \utilities instead of C:\utilities. Information is lost because it can be C,D,E or whatewer, which needs to be validated by other functions like GetFullPathNameW or by setting global state etc.

[likle]

Thanks @kampeador , I understand your issue. I will have to think about that and whether I can do something about it.