[gcc r13-1512] libstdc++: testsuite: why cast getpid result

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:bd2d0aab4d259fe579db294467c366b7737f3488

commit r13-1512-gbd2d0aab4d259fe579db294467c366b7737f3488
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Tue Jul 5 19:07:32 2022 -0300

    libstdc++: testsuite: why cast getpid result
    
    Add a comment next to the getpid call to explain why the typecast is
    needed.
    
    
    for  libstdc++-v3/ChangeLog
    
            * testsuite/util/testsuite_fs.h (nonexistent_path): Explain
            why we need the typecast.

Diff:
---
 libstdc++-v3/testsuite/util/testsuite_fs.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/util/testsuite_fs.h b/libstdc++-v3/testsuite/util/testsuite_fs.h
index 25f8f734dc7..0e28385e99a 100644
--- a/libstdc++-v3/testsuite/util/testsuite_fs.h
+++ b/libstdc++-v3/testsuite/util/testsuite_fs.h
@@ -162,7 +162,8 @@ namespace __gnu_test
     if (file.length() > 64)
       file.resize(64);
     // The combination of random counter and PID should be unique for a given
-    // run of the testsuite.
+    // run of the testsuite.  N.B. getpid() returns a pointer type on vxworks
+    // in kernel mode.
     file += std::to_string((unsigned long) ::getpid());
     p = std::move(file);
     if (test_fs::exists(p))