[gcc r10-9589] libstdc++: Make "nonexistent" paths less predictable in filesystem tests

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:86116175a37f9861a233fb0a53b6d904dcfa1833

commit r10-9589-g86116175a37f9861a233fb0a53b6d904dcfa1833
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Feb 12 15:13:02 2021 +0000

    libstdc++: Make "nonexistent" paths less predictable in filesystem tests
    
    The helper function for creating new paths doesn't work well on Windows,
    because the PID of a process started by Wine is very consistent and so
    the same path gets created each time.
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/util/testsuite_fs.h (nonexistent_path): Add
            random number to the path.
    
    (cherry picked from commit 4179ec107943bea360b8aa75e29e2c5ad9f13e9e)

Diff:
---
 libstdc++-v3/testsuite/util/testsuite_fs.h | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/testsuite/util/testsuite_fs.h b/libstdc++-v3/testsuite/util/testsuite_fs.h
index 76d5e218924..69e5edc3cd4 100644
--- a/libstdc++-v3/testsuite/util/testsuite_fs.h
+++ b/libstdc++-v3/testsuite/util/testsuite_fs.h
@@ -34,8 +34,13 @@ namespace test_fs = std::experimental::filesystem;
 #include <fstream>
 #include <string>
 #include <cstdio>
-#include <stdlib.h>
-#include <unistd.h>
+
+#if defined(_GNU_SOURCE) || _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L
+#include <stdlib.h> // mkstemp
+#include <unistd.h> // unlink, close
+#else
+#include <random>   // std::random_device
+#endif
 
 namespace __gnu_test
 {
@@ -121,13 +126,13 @@ namespace __gnu_test
     if (file.length() > 64)
       file.resize(64);
     char buf[128];
-    static int counter;
+    static unsigned counter = std::random_device{}();
 #if _GLIBCXX_USE_C99_STDIO
     std::snprintf(buf, 128,
 #else
     std::sprintf(buf,
 #endif
-      "filesystem-test.%d.%lu-%s", counter++, (unsigned long) ::getpid(),
+      "filesystem-test.%u.%lu-%s", counter++, (unsigned long) ::getpid(),
       file.c_str());
     p = buf;
 #endif