[libcxx] [test] Fix path.modifiers/make_preferred for windows

[mstorsjo]

Summary

Use p.string() instead of p.native() for comparing with the expected value.

Explicitly list the expected values for both posix and windos, even if the operation is an identity operation on posix.

[ldionne]

libcxx/test/std/input.output/filesystems/class.path/path.member/path.modifiers/make_preferred.pass.cpp

35–41

I would rather this be changed to:

struct MakePreferredTestcase {
  const char* value;
  const char* expected_posix;
  const char* expected_windows;
};

and then

const MakePreferredTestcase TestCases[] = {
      {"", "", ""}
    , {"hello_world", "", ""}
    , {"/", "/", "\\"}
    , {"/foo/bar/baz/", "/foo/bar/baz/", "\\foo\\bar\\baz\\"}
    , {"\\", "\\", "\\"}
    , ...
};

I find it easier to follow.

[mstorsjo]

Updated according to suggestions.

[mstorsjo]

@ldionne Any more comments on this?

libcxx/test/std/input.output/filesystems/class.path/path.member/path.modifiers/make_preferred.pass.cpp

 #include "test_macros.h"
 #include "test_iterators.h"
 #include "count_new.h"
 #include "filesystem_test_helper.h"
 
 
 struct MakePreferredTestcase {
   const char* value;
+  const char* expected_posix;
+  const char* expected_windows;
 };
 
 const MakePreferredTestcase TestCases[] =
   {
-      {""}
-    , {"hello_world"}
-    , {"/"}
-    , {"/foo/bar/baz/"}
-    , {"\\"}
-    , {"\\foo\\bar\\baz\\"}
-    , {"\\foo\\/bar\\/baz\\"}
+      {"", "", ""}
+    , {"hello_world", "hello_world", "hello_world"}
+    , {"/", "/", "\\"}
+    , {"/foo/bar/baz/", "/foo/bar/baz/", "\\foo\\bar\\baz\\"}
+    , {"\\", "\\", "\\"}
+    , {"\\foo\\bar\\baz\\", "\\foo\\bar\\baz\\", "\\foo\\bar\\baz\\"}
+    , {"\\foo\\/bar\\/baz\\", "\\foo\\/bar\\/baz\\", "\\foo\\\\bar\\\\baz\\"}
   };
 
 int main(int, char**)
 {
   // This operation is an identity operation on linux.
+  // On windows, compare with preferred_win, if set.
   using namespace fs;
   for (auto const & TC : TestCases) {
     path p(TC.value);
     assert(p == TC.value);
     path& Ref = (p.make_preferred());
-    assert(p.native() == TC.value);
+#ifdef _WIN32
+    std::string s(TC.expected_windows);
+#else
+    std::string s(TC.expected_posix);
+#endif
+    assert(p.string() == s);
     assert(&Ref == &p);
   }
 
   return 0;
 }