Miscellaneous sys/ucontext.h namespace fixes (bug 21457).

This patch fixes various miscellaneous namespace issues in
sys/ucontext.h headers.

Some struct tags are removed where the structs also have *_t typedef
names, while other struct tags without such names are renamed to start
__; the changes are noted in NEWS as they can affect C++ name mangling
(although there seems to be little if any external use of these types,
at least based on checking codesearch.debian.net).  For powerpc,
pointers to struct pt_regs (not defined in this header) are changed to
point to struct __ctx(pt_regs), so in the __USE_MISC case those struct
fields continue to point to the existing struct pt_regs type for
maximum compatibility, while when that's a namespace issue they point
to a struct __pt_regs type which is always an incomplete struct.

Tested for affected architectures with build-many-glibcs.py.

	[BZ #21457]
	* sysdeps/unix/sysv/linux/m68k/sys/ucontext.h (fpregset_t): Remove
	struct tag.
	* sysdeps/unix/sysv/linux/mips/sys/ucontext.h (fpregset_t):
	Likewise.
	* sysdeps/unix/sysv/linux/nios2/sys/ucontext.h (mcontext_t):
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h (pt_regs):
	Declare struct type with __ctx.
	[__WORDSIZE != 32] (mcontext_t): Use __ctx with pt_regs struct
	tag.
	(ucontext_t) [__WORDSIZE == 32]: Use __ctx with pt_regs struct tag
	and regs field name.

1 files changed, 6 insertions, 4 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h b/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
index 217748784c..54fe9df601 100644
--- a/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
+++ b/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
@@ -31,6 +31,8 @@
 # define __ctx(fld) __ ## fld
 #endif
 
+struct __ctx(pt_regs);
+
 #if __WORDSIZE == 32
 
 /* Number of general registers.  */
@@ -117,7 +119,7 @@ typedef struct {
 	int		__pad0;
 	unsigned long	__ctx(handler);
 	unsigned long	__ctx(oldmask);
-	struct pt_regs	*__ctx(regs);
+	struct __ctx(pt_regs)	*__ctx(regs);
 	gregset_t	__ctx(gp_regs);
 	fpregset_t	__ctx(fp_regs);
 /*
@@ -145,8 +147,6 @@ typedef struct {
 
 #endif
 
-#undef __ctx
-
 /* Userlevel context.  */
 typedef struct ucontext_t
   {
@@ -179,7 +179,7 @@ typedef struct ucontext_t
      */
     int uc_pad[7];
     union uc_regs_ptr {
-      struct pt_regs *regs;
+      struct __ctx(pt_regs) *__ctx(regs);
       mcontext_t *uc_regs;
     } uc_mcontext;
     sigset_t    uc_sigmask;
@@ -190,4 +190,6 @@ typedef struct ucontext_t
 #endif
   } ucontext_t;
 
+#undef __ctx
+
 #endif /* sys/ucontext.h */