htl: Add __errno_location and __h_errno_location

As explained on
https://sourceware.org/ml/libc-alpha/2020-01/msg00049.html
the presence of __errno_location in libpthread.so on GNU/Linux makes
libpthread getting linked in for libstdc++. This aligns on that behavior, to
avoid issues that only GNU/Hurd would get.

3 files changed, 36 insertions, 0 deletions

diff --git a/htl/Makefile b/htl/Makefile
index e091077..b9d3831 100644
--- a/htl/Makefile
+++ b/htl/Makefile
@@ -134,6 +134,7 @@ libpthread-routines := pt-attr pt-attr-destroy pt-attr-getdetachstate	    \
 	shm-directory							    \
 									    \
 	cthreads-compat							    \
+	herrno								    \
 	$(SYSDEPS)
 
 headers :=				\
diff --git a/htl/Versions b/htl/Versions
index c5a616d..1c306ac 100644
--- a/htl/Versions
+++ b/htl/Versions
@@ -29,6 +29,7 @@ libc {
 libpthread {
   GLIBC_2.2.6 {
     _IO_flockfile; _IO_ftrylockfile; _IO_funlockfile;
+    __errno_location; __h_errno_location;
   }
   GLIBC_2.12 {
     __pthread_errorcheck_mutexattr; __pthread_recursive_mutexattr;
diff --git a/htl/herrno.c b/htl/herrno.c
new file mode 100644
index 0000000..66174a0
--- /dev/null
+++ b/htl/herrno.c
@@ -0,0 +1,34 @@
+/* Copyright (C) 1996-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <features.h>
+#include <netdb.h>
+#undef h_errno
+
+#include <tls.h>
+
+/* We need to have the error status variable of the resolver
+   accessible in the libc.  */
+extern __thread int __h_errno;
+
+
+/* When threaded, h_errno may be a per-thread variable.  */
+int *
+__h_errno_location (void)
+{
+  return &__h_errno;
+}