[gcc r12-6867] libstdc++: Define _GNU_SOURCE for secure_getenv on Cygwin [PR104217]

[Jonathan Wakely]

https://gcc.gnu.org/g:e20486d508afdf22790a271e90ca76d8df5fa7a5

commit r12-6867-ge20486d508afdf22790a271e90ca76d8df5fa7a5
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jan 25 10:11:36 2022 +0000

    libstdc++: Define _GNU_SOURCE for secure_getenv on Cygwin [PR104217]
    
    For GNU/Linux G++ defines _GNU_SOURCE automatically, but not for Cygwin.
    This means secure_getenv is not declared by Cygwin's <stdlib.h>, even
    though autoconf detected it is present in the library. Define it in the
    source files that want to use secure_getenv.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/104217
            * src/c++17/fs_ops.cc (_GNU_SOURCE): Define.
            * src/filesystem/dir.cc (_GNU_SOURCE): Define.
            * src/filesystem/ops.cc (_GNU_SOURCE): Define.

Diff:
---
 libstdc++-v3/src/c++17/fs_ops.cc   | 4 ++++
 libstdc++-v3/src/filesystem/dir.cc | 4 ++++
 libstdc++-v3/src/filesystem/ops.cc | 4 ++++
 3 files changed, 12 insertions(+)

diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index 1d3693af06c..321944d73f7 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -27,6 +27,10 @@
 # define NEED_DO_COPY_FILE
 # define NEED_DO_SPACE
 #endif
+#ifndef _GNU_SOURCE
+// Cygwin needs this for secure_getenv
+# define _GNU_SOURCE 1
+#endif
 
 #include <bits/largefile-config.h>
 #include <filesystem>
diff --git a/libstdc++-v3/src/filesystem/dir.cc b/libstdc++-v3/src/filesystem/dir.cc
index f1bf96aab50..d5b11f25297 100644
--- a/libstdc++-v3/src/filesystem/dir.cc
+++ b/libstdc++-v3/src/filesystem/dir.cc
@@ -25,6 +25,10 @@
 #ifndef _GLIBCXX_USE_CXX11_ABI
 # define _GLIBCXX_USE_CXX11_ABI 1
 #endif
+#ifndef _GNU_SOURCE
+// Cygwin needs this for secure_getenv
+# define _GNU_SOURCE 1
+#endif
 
 #include <bits/largefile-config.h>
 #include <experimental/filesystem>
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 324c6afc7a9..cd98caf73f2 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -27,6 +27,10 @@
 # define NEED_DO_COPY_FILE
 # define NEED_DO_SPACE
 #endif
+#ifndef _GNU_SOURCE
+// Cygwin needs this for secure_getenv
+# define _GNU_SOURCE 1
+#endif
 
 #include <bits/largefile-config.h>
 #include <experimental/filesystem>