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, 30 insertions, 14 deletions

diff --git a/bits/errno.h b/bits/errno.h
index cd4fcfa428..11180711d7 100644
--- a/bits/errno.h
+++ b/bits/errno.h
@@ -1,4 +1,5 @@
-/* Copyright (C) 1991-2017 Free Software Foundation, Inc.
+/* Error constants.  Generic version.
+   Copyright (C) 1991-2017 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
@@ -15,20 +16,35 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-/* This file defines the `errno' constants.  */
+/* This file defines the errno constants.  */
 
-#if !defined __Emath_defined && (defined _ERRNO_H || defined __need_Emath)
-#undef	__need_Emath
-#define	__Emath_defined	1
+#ifndef _BITS_ERRNO_H
+#define _BITS_ERRNO_H 1
 
-# define EDOM	XXX	<--- fill in what is actually needed
-# define EILSEQ	XXX	<--- fill in what is actually needed
-# define ERANGE	XXX	<--- fill in what is actually needed
+#if !defined _ERRNO_H
+# error "Never include <bits/errno.h> directly; use <errno.h> instead."
 #endif
 
-#ifdef	_ERRNO_H
-# error "Define here all the missing error messages for the port.  These"
-# error "must match the numbers of the kernel."
-# define Exxxx	XXX
-...
-#endif
+#error "Generic bits/errno.h included -- port is incomplete."
+
+/* Authors of new ports of the GNU C Library must override this file
+   with their own bits/errno.h in an appropriate subdirectory of
+   sysdeps/.  Its function is to define all of the error constants
+   from C2011 and POSIX.1-2008, with values appropriate to the
+   operating system, and any additional OS-specific error constants.
+
+   C2011 requires all error constants to be object-like macros that
+   expand to "integer constant expressions with type int, positive
+   values, and suitable for use in #if directives".  Moreover, all of
+   their names must begin with a capital E, followed immediately by
+   either another capital letter, or a digit.  It is OK to define
+   macros that are not error constants, but only in the implementation
+   namespace.
+
+   errno.h is sometimes included from assembly language.  Therefore,
+   when __ASSEMBLER__ is defined, bits/errno.h may only define macros;
+   it may not make any other kind of C declaration or definition.
+   Also, the error constants should, if at all possible, expand to
+   simple decimal or hexadecimal numbers.  */
+
+#endif /* bits/errno.h.  */