Fix struct sigaltstack namespace (bug 21517).

glibc defines the stack_t type with the tag struct sigaltstack.  This
is not permitted by POSIX; sigaltstack is only reserved with file
scope in the namespace of ordinary identifiers, not the tag namespace,
and in the case where stack_t is obtained from ucontext.h rather than
signal.h, it's not reserved with file scope at all.

This patch removes the tag accordingly and updates uses in glibc of
struct sigaltstack.  This is similar to the removal of the "struct
siginfo" tag a few years ago: C++ name mangling changes are an
unavoidable consequence.  A NEWS item is added to note the changed
mangling.  There is inevitably some risk of breaking builds of
anything that relies on the struct sigaltstack name (though the first
few hits I looked at from codesearch.debian.net generally seemed to
involve code that could use the stack_t name conditionally, so
depending on how they determine the conditionals they may work with
glibc not defining the struct tag anyway).

Tested for x86_64 and x86, and with build-many-glibcs.py.

	[BZ #21517]
	* bits/types/stack_t.h (stack_t): Remove struct tag.
	* sysdeps/unix/sysv/linux/bits/types/stack_t.h (stack_t):
	Likewise.
	* sysdeps/unix/sysv/linux/mips/bits/types/stack_t.h (stack_t):
	Likewise.
	* debug/segfault.c (install_handler): Use stack_t instead of
	struct sigaltstack.
	* hurd/hurd/signal.h (struct hurd_sigstate): Likewise.
	* hurd/trampoline.c (_hurd_setup_sighandler): Likewise.
	* include/signal.h (__sigaltstack): Likwise.
	* signal/sigaltstack.c (__sigaltstack): Likewise.
	* signal/signal.h (sigaltstack): Likewise.
	* sysdeps/mach/hurd/i386/signal-defines.sym
	(SIGALTSTACK__SS_SP__OFFSET): Likewise.
	(SIGALTSTACK__SS_SIZE__OFFSET): Likewise.
	(SIGALTSTACK__SS_FLAGS__OFFSET): Likewise.
	* sysdeps/mach/hurd/sigaltstack.c (__sigaltstack): Likewise.
	* sysdeps/mach/hurd/sigstack.c (sigstack): Likewise.
	* sysdeps/unix/sysv/linux/alpha/sys/procfs.h (struct
	elf_prstatus): Likewise.
	* sysdeps/unix/sysv/linux/hppa/____longjmp_chk.c (CHECK_SP):
	Likewise.
	* sysdeps/unix/sysv/linux/ia64/sys/procfs.h (struct elf_prstatus):
	Likewise.
	* sysdeps/unix/sysv/linux/m68k/____longjmp_chk.c (CHECK_SP):
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/sys/procfs.h (struct
	elf_prstatus): Likewise.
	* sysdeps/unix/sysv/linux/sh/sys/procfs.h (struct elf_prstatus):
	Likewise.
	* sysdeps/unix/sysv/linux/sys/procfs.h (struct elf_prstatus):
	Likewise.

3 files changed, 7 insertions, 7 deletions

diff --git a/sysdeps/mach/hurd/i386/signal-defines.sym b/sysdeps/mach/hurd/i386/signal-defines.sym
index 9521bd723c..e42bbbe061 100644
--- a/sysdeps/mach/hurd/i386/signal-defines.sym
+++ b/sysdeps/mach/hurd/i386/signal-defines.sym
@@ -5,6 +5,6 @@
 
 HURD_SIGSTATE__SIGALTSTACK__OFFSET	offsetof(struct hurd_sigstate, sigaltstack)
 
-SIGALTSTACK__SS_SP__OFFSET		offsetof(struct sigaltstack, ss_sp)
-SIGALTSTACK__SS_SIZE__OFFSET		offsetof(struct sigaltstack, ss_size)
-SIGALTSTACK__SS_FLAGS__OFFSET		offsetof(struct sigaltstack, ss_flags)
+SIGALTSTACK__SS_SP__OFFSET		offsetof(stack_t, ss_sp)
+SIGALTSTACK__SS_SIZE__OFFSET		offsetof(stack_t, ss_size)
+SIGALTSTACK__SS_FLAGS__OFFSET		offsetof(stack_t, ss_flags)
diff --git a/sysdeps/mach/hurd/sigaltstack.c b/sysdeps/mach/hurd/sigaltstack.c
index 06a6a5c112..4fba69e766 100644
--- a/sysdeps/mach/hurd/sigaltstack.c
+++ b/sysdeps/mach/hurd/sigaltstack.c
@@ -22,16 +22,16 @@
 /* Run signals handlers on the stack specified by SS (if not NULL).
    If OSS is not NULL, it is filled in with the old signal stack status.  */
 int
-__sigaltstack (const struct sigaltstack *argss, struct sigaltstack *oss)
+__sigaltstack (const stack_t *argss, stack_t *oss)
 {
   struct hurd_sigstate *s;
-  struct sigaltstack ss, old;
+  stack_t ss, old;
 
   /* Fault before taking any locks.  */
   if (argss != NULL)
     ss = *argss;
   if (oss != NULL)
-    *(volatile struct sigaltstack *) oss = *oss;
+    *(volatile stack_t *) oss = *oss;
 
   s = _hurd_self_sigstate ();
   __spin_lock (&s->lock);
diff --git a/sysdeps/mach/hurd/sigstack.c b/sysdeps/mach/hurd/sigstack.c
index a3a11f9772..484efb627a 100644
--- a/sysdeps/mach/hurd/sigstack.c
+++ b/sysdeps/mach/hurd/sigstack.c
@@ -24,7 +24,7 @@
 int
 sigstack (struct sigstack *ss, struct sigstack *oss)
 {
-  struct sigaltstack as, oas;
+  stack_t as, oas;
 
   as.ss_sp = ss->ss_sp;
   as.ss_size = 0;