[libcxx] [test] Make filesystem tests not rely on libc++ internals

[mstorsjo]

Summary

As part of https://reviews.llvm.org/D119036
(506cf6dc048835c598b654e43ed8f723a42e39ba), -DNOMINMAX was
dropped from the Windows CI configurations, replaced with a
block with _LIBCPP_PUSH_MACROS, #include <__undef_macros>
and _LIBCPP_POP_MACROS (and
ADDITIONAL_COMPILE_FLAGS: -DNOMINMAX left in two tests).

However, this workaround breaks the running the libc++ tests
against a different C++ standard library than libc++, as those
macros and that header are libc++ internals.

This works around it by simply doing #undef min and #undef max
(when on Windows), making the tests work on other C++ standard
libraries again.

[ldionne]

libcxx/test/support/filesystem_test_helper.h

35

Instead, could we guard against those macros by doing something like (std::numeric_limits<large_file_offset_t>::max)()?

Otherwise, we could also add -DNOMINMAX in the testing config when we're on Windows. I'm not a huge fan of undef'ing those macros here in this file, it seems kind of ad-hoc.

[ldionne]

libcxx/test/support/filesystem_test_helper.h

35

Yeah, FWIW, I think this is where I made a mistake: https://reviews.llvm.org/D119036#3301636

I should have left -DNOMINMAX in place, at least on Windows.

[mstorsjo]

libcxx/test/support/filesystem_test_helper.h

35

Yeah I don't mind putting that define back.

[mstorsjo]

Reinstate -DNOMINMAX instead of using libc++ specifics in filesystem_test_helper.h.

[mstorsjo]

Add an extra -Wno-macro-redefined in a test that includes libcxx internal headers (which also define NOMINMAX). Will push later if CI is passing.

libcxx/test/support/filesystem_test_helper.h

 #include "format_string.h"
 
 // For creating socket files
 #if !defined(__FreeBSD__) && !defined(__APPLE__) && !defined(_WIN32)
 # include <sys/socket.h>
 # include <sys/un.h>
 #endif
 
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
+#ifdef _WIN32
+// If built without -DNOMINMAX, Windows system headers can pollute the
+// namespace with min/max defines that break standard C++.
+#undef min
+#undef max
+#endif
 
 namespace utils {
 #ifdef _WIN32
     inline int mkdir(const char* path, int mode) { (void)mode; return ::_mkdir(path); }
     inline int ftruncate(int fd, off_t length) { return ::_chsize(fd, length); }
     inline int symlink(const char* oldname, const char* newname, bool is_dir) {
         DWORD flags = is_dir ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0;
         if (CreateSymbolicLinkA(newname, oldname,
for (const auto &ent : fs::directory_iterator(root, ec)) {
     }
     return ent;
   }
   fprintf(stderr, "No inaccessible directory \"%s\" found, skipping tests "
                   "regarding it\n", dir.string().c_str());
   return fs::path();
 }
 
-_LIBCPP_POP_MACROS
-
 #endif /* FILESYSTEM_TEST_HELPER_H */