Remove __need macros from errno.h (__need_Emath, __need_error_t).

This is fairly complicated, not because the users of __need_Emath and
__need_error_t have complicated requirements, but because the core
changes had a lot of fallout.

__need_error_t exists for gnulib compatibility in argz.h and argp.h.
error_t itself is a Hurdism, an enum containing all the E-constants,
so you can do 'p (error_t) errno' in gdb and get a symbolic value.
argz.h and argp.h use it for function return values, and they want to
fall back to 'int' when that's not available.  There is no reason why
these nonstandard headers cannot just go ahead and include all of
errno.h; so we do that.

__need_Emath is defined only by .S files; what they _really_ need is
for errno.h to avoid declaring anything other than the E-constants
(e.g. 'extern int __errno_location(void);' is a syntax error in
assembly language). This is replaced with a check for __ASSEMBLER__ in
errno.h, plus a carefully documented requirement for bits/errno.h not
to define anything other than macros.  That in turn has the
consequence that bits/errno.h must not define errno - fortunately, all
live ports use the same definition of errno, so I've moved it to
errno.h.  The Hurd bits/errno.h must also take care not to define
error_t when __ASSEMBLER__ is defined, which involves repeating all of
the definitions twice, but it's a generated file so that's okay.

	* stdlib/errno.h: Remove __need_Emath and __need_error_t logic.
	Reorganize file.  Declare errno here.  When __ASSEMBLER__ is
	defined, don't declare anything other than the E-constants.

	* include/errno.h: Change conditional for exposing internal
	declarations to (not _ISOMAC and not __ASSEMBLER__).
	* bits/errno.h: Remove logic for __need_Emath.  Document
	requirements for a port-specific bits/errno.h.

	* sysdeps/unix/sysv/linux/bits/errno.h
	* sysdeps/unix/sysv/linux/alpha/bits/errno.h
	* sysdeps/unix/sysv/linux/hppa/bits/errno.h
	* sysdeps/unix/sysv/linux/mips/bits/errno.h
	* sysdeps/unix/sysv/linux/sparc/bits/errno.h:
	Add multiple-include guard and check against improper inclusion.
	Remove __need_Emath logic.  Don't declare errno here.  Ensure all
	constants are defined as simple integer literals.  Consistent
	formatting.
	* sysdeps/mach/hurd/errnos.awk: Likewise.  Only define error_t and
	enum __error_t_codes if __ASSEMBLER__ is not defined.
	* sysdeps/mach/hurd/bits/errno.h: Regenerate.

	* argp/argp.h, string/argz.h: Don't define __need_error_t before
	including errno.h.
	* sysdeps/i386/i686/fpu/multiarch/s_cosf-sse2.S
	* sysdeps/i386/i686/fpu/multiarch/s_sincosf-sse2.S
	* sysdeps/i386/i686/fpu/multiarch/s_sinf-sse2.S
	* sysdeps/x86_64/fpu/s_cosf.S
	* sysdeps/x86_64/fpu/s_sincosf.S
	* sysdeps/x86_64/fpu/s_sinf.S:
	Just include errno.h; don't define __need_Emath or include
	bits/errno.h directly.

1 files changed, 4 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 991ee63f7c..8d35bd6c95 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,10 @@ Version 2.26
   transliteration tables are all updated to Unicode 9.0.0, using
   generator scripts contributed by Mike FABIAN (Red Hat).
 
+* errno.h is now safe to use from C-preprocessed assembly language on all
+  supported operating systems.  In this context, it will only define the
+  Exxxx constants, as preprocessor macros expanding to integer literals.
+
 * The rpcgen, librpcsvc and related headers will only be built and
   installed when glibc is configured with --enable-obsolete-rpc.
   This allows alternative RPC implementations, like TIRPC, to be used