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 --git a/libstdc++-v3/testsuite/util/testsuite_fs.h b/libstdc++-v3/testsuite/util/testsuite_fs.h
index 25f8f73..0e28385 100644
--- a/libstdc++-v3/testsuite/util/testsuite_fs.h
+++ b/libstdc++-v3/testsuite/util/testsuite_fs.h
@@ -162,7 +162,8 @@
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))
