Give libcxx tests temporary filenames that are actually unique.

[jroelofs]

Summary

With newlib as the libc, the following program would print out the same filename twice:

#include "support/platform_support.h"
#include <iostream>
int main() {
std::string temp1 = get_temp_file_name();
std::string temp2 = get_temp_file_name();
std::cout << temp1 << " " << temp2 << std::endl;
}

This breaks a few of the tests similar to input.output/file.streams/fstreams/filebuf.assign/member_swap.pass.cpp which expect the returned filenames to be different.

This patch fixes that bug by creating a TempFileName class which, on construction, is guaranteed to have a unique name.

Please double check the Windows side of the TempFileName class with extra scrutiny. I have neither tested, nor built this on Windows (and I don't have a machine to try it out on either).

[danalbert]

test/support/platform_support.h

55

It's actually a TempFile, not a TempFileName, since you leave the fd open. I think what you actually wanted was to mkstemp(), stash the name and then close the fd (before leaving the constructor).

76

I must be missing something here... std::remove() takes three arguments.

[jroelofs]

test/support/platform_support.h

44

s/algorithm/cstdio/

yikes. I guess it builds with out this include...

55

Oh good point. For some reason, I thought I needed to keep the fd open in order to keep the file name unique between concurrent processes running these tests.... but after reading the doc again, I guess not.

76

There's another std::remove... bad naming, as it does something completely different than the version you're thinking of.

http://en.cppreference.com/w/cpp/io/c/remove

[jroelofs]

Update the patch to reflect @danalbert's comments.

[jroelofs]

r215977

test/support/platform_support.h

 std::string
 get_temp_file_name()
 {
-   std::string s("temp.XXXXXX");
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
-   _mktemp(&s[0]);
+    char Path[MAX_PATH+1];
+    char FN[MAX_PATH+1];
+    do { } while (0 == GetTempPath(MAX_PATH+1, Path));
+    do { } while (0 == GetTempFile(Path, "libcxx", 0, FN));
+    return FN;
 #else
-   mktemp(&s[0]);
+    std::string Name;
+    int FD = -1;
+    do {
+      Name = "libcxx.XXXXXX";
+      FD = mkstemp(&Name[0]);
+      assert(errno != EINVAL && "Something is wrong with the mkstemp's argument");
+    } while (FD == -1 || errno == EEXIST);
+    close(FD);
+    return Name;
 #endif
-   return s;
 }
 
 #endif // PLATFORM_SUPPORT_H