[Bug libstdc++/88881] std::filesystem::status gives bad results on mingw32

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88881

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
But that fix looks wrong, it means "file/" will resolve to "file" and that's
wrong a for a non-directory, because "file/" should fail.

Testcase demonstrating the mingw bugs:

#include <sys/stat.h>
#include <stdio.h>

void print(const char* s, int i, int expected)
{
  printf("%-26s %2d %s\n", s, i, i == expected ? "" : " FAIL");
}

void f1()
{
  struct stat st;
  int i;
  i = stat(".\\", &st);
  print("stat(\".\\\")", i, 0);
  i = stat(".\\nonesuch\\..", &st);
  print("stat(\".\\nonesuch\\..\")", i, -1);

  // Trailing slash after a non-directory should fail:
  i = stat("a.exe\\", &st);
  print("stat(\"a.exe\\\")", i, -1);
  // "/." after a non-directory is also wrong:
  i = stat("a.exe\\.", &st);
  print("stat(\"a.exe\\.\")", i, -1);
  // And resolving "/dir/.." after a non-directory is also wrong:
  i = stat("a.exe\\nonesuch\\..", &st);
  print("stat(\"a.exe\\nonesuch\\..\")", i, -1);
}

void f2()
{
  struct _stat st;
  int i;
  i = _stat(".\\", &st);
  print("_stat(\".\\\")", i, 0);
  i = _stat(".\\nonesuch\\..", &st);
  print("_stat(\".\\nonesuch\\..\")", i, -1);
}

void f3()
{
  struct _stat st;
  int i;
  i = _wstat(L".\\", &st);
  print("_wstat(L\".\\\")", i, 0);
  i = _wstat(L".\\nonesuch\\..", &st);
  print("_wstat(L\".\\nonesuch\\..\")", i, -1);
}

int main()
{
  f1();
  f2();
  f3();
}


Output for mingw-w64 5.0

stat(".\")                  0 
stat(".\nonesuch\..")       0  FAIL
stat("a.exe\")              0  FAIL
stat("a.exe\.")             0  FAIL
stat("a.exe\nonesuch\..")   0  FAIL
_stat(".\")                -1  FAIL
_stat(".\nonesuch\..")      0  FAIL
_wstat(L".\")              -1  FAIL
_wstat(L".\nonesuch\..")    0  FAIL