libstdc++: Use secure_getenv for filesystem::temp_directory_path() [PR65018]

This adds a configure check for the GNU extension secure_getenv and then
uses it for looking up TMPDIR and similar variables.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/65018
	* configure.ac: Check for secure_getenv.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* src/filesystem/ops-common.h (get_temp_directory_from_env): New
	helper function to obtain path from the environment.
	* src/c++17/fs_ops.cc (fs::temp_directory_path): Use new helper.
	* src/filesystem/ops.cc (fs::temp_directory_path): Likewise.
	* testsuite/27_io/filesystem/operations/temp_directory_path.cc:
	Print messages if test cannot be run.
	* testsuite/experimental/filesystem/operations/temp_directory_path.cc:
	Likewise. Fix incorrect condition. Use "TMP" to work with
	Windows as well as POSIX.

2 files changed, 45 insertions, 27 deletions

diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index 43311e6..b8bbf44 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -568,6 +568,46 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
 
 #endif // _GLIBCXX_HAVE_SYS_STAT_H
 
+  // Find OS-specific name of temporary directory from the environment,
+  // Caller must check that the path is an accessible directory.
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+  inline wstring
+  get_temp_directory_from_env()
+  {
+    unsigned len = 1024;
+    std::wstring buf;
+    do
+      {
+	buf.resize(len);
+	len = GetTempPathW(buf.size(), buf.data());
+      } while (len > buf.size());
+
+    if (len == 0)
+      {
+	ec.assign((int)GetLastError(), std::system_category());
+	return p;
+      }
+    buf.resize(len);
+    return buf;
+  }
+#else
+  inline const char*
+  get_temp_directory_from_env() noexcept
+  {
+    for (auto env : { "TMPDIR", "TMP", "TEMP", "TEMPDIR" })
+      {
+#if _GLIBCXX_HAVE_SECURE_GETENV
+	auto tmpdir = ::secure_getenv(env);
+#else
+	auto tmpdir = ::getenv(env);
+#endif
+	if (tmpdir)
+	  return tmpdir;
+      }
+    return "/tmp";
+  }
+#endif
+
 _GLIBCXX_END_NAMESPACE_FILESYSTEM
 
 _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 7c5b164..3494cbd 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -1289,7 +1289,8 @@ fs::system_complete(const path& p, error_code& ec)
 #endif
 }
 
-fs::path fs::temp_directory_path()
+fs::path
+fs::temp_directory_path()
 {
   error_code ec;
   path tmp = temp_directory_path(ec);
@@ -1298,31 +1299,10 @@ fs::path fs::temp_directory_path()
   return tmp;
 }
 
-fs::path fs::temp_directory_path(error_code& ec)
+fs::path
+fs::temp_directory_path(error_code& ec)
 {
-  path p;
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
-  unsigned len = 1024;
-  std::wstring buf;
-  do
-    {
-      buf.resize(len);
-      len = GetTempPathW(buf.size(), buf.data());
-    } while (len > buf.size());
-
-  if (len == 0)
-    {
-      ec.assign((int)GetLastError(), std::system_category());
-      return p;
-    }
-  buf.resize(len);
-  p = std::move(buf);
-#else
-  const char* tmpdir = nullptr;
-  const char* env[] = { "TMPDIR", "TMP", "TEMP", "TEMPDIR", nullptr };
-  for (auto e = env; tmpdir == nullptr && *e != nullptr; ++e)
-    tmpdir = ::getenv(*e);
-  p = tmpdir ? tmpdir : "/tmp";
+  path p = fs::get_temp_directory_from_env();
   auto st = status(p, ec);
   if (ec)
     p.clear();
@@ -1331,7 +1311,5 @@ fs::path fs::temp_directory_path(error_code& ec)
       p.clear();
       ec = std::make_error_code(std::errc::not_a_directory);
     }
-#endif
   return p;
 }
-