Fix GCC 11 -Warray-parameter warning for __sigsetjmp (bug 26647)

This patch fixes part of bug 26647 (-Werror=array-parameter error
building with GCC 11 because of __sigsetjmp being declared using an
array parameter in one header and a pointer parameter in another).

The fix is to split the struct __jmp_buf_tag definition out to a
separate bits/types/ header so it can be included in pthread.h, so
that pthread.h can declare __sigsetjmp with the type contents visible,
so can use an array (as in setjmp.h) rather than a pointer in the
declaration.

Note that several other build failures with GCC 11 remain.  This does
not fix the jmp_buf-related -Wstringop-overflow errors (also discussed
in bug 26647), or -Warray-parameter errors for other functions (bug
26686), or -Warray-bounds errors (bug 26687).

Tested, with older compilers, natively for x86_64 and with
build-many-glibc.py for aarch64-linux-gnu.  Tested with
build-many-glibcs.py with GCC mainline for aarch64-linux-gnu that this
gets past the -Warray-parameter issue for __sigsetjmp (with the next
build failure being the other one discussed in bug 26647).

1 files changed, 37 insertions, 0 deletions

diff --git a/setjmp/bits/types/struct___jmp_buf_tag.h b/setjmp/bits/types/struct___jmp_buf_tag.h
new file mode 100644
index 0000000000..9d8634f1e4
--- /dev/null
+++ b/setjmp/bits/types/struct___jmp_buf_tag.h
@@ -0,0 +1,37 @@
+/* Define struct __jmp_buf_tag.
+   Copyright (C) 1991-2020 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/>.  */
+
+#ifndef	__jmp_buf_tag_defined
+#define	__jmp_buf_tag_defined 1
+
+#include <bits/setjmp.h>		/* Get `__jmp_buf'.  */
+#include <bits/types/__sigset_t.h>
+
+/* Calling environment, plus possibly a saved signal mask.  */
+struct __jmp_buf_tag
+  {
+    /* NOTE: The machine-dependent definitions of `__sigsetjmp'
+       assume that a `jmp_buf' begins with a `__jmp_buf' and that
+       `__mask_was_saved' follows it.  Do not move these members
+       or add others before it.  */
+    __jmp_buf __jmpbuf;		/* Calling environment.  */
+    int __mask_was_saved;	/* Saved the signal mask?  */
+    __sigset_t __saved_mask;	/* Saved signal mask.  */
+  };
+
+#endif