Post-cleanup 2: minimize _G_config.h.

Nearly everything in _G_config.h is either junk or more appropriately
defined elsewhere:

 * _G_fpos_t, _G_fpos64_t, and _G_BUFSIZ are already completely unused.
 * All remaining uses of _G_va_list have been changed to __gnuc_va_list.
 * The definition of _G_HAVE_ST_BLKSIZE/_IO_HAVE_ST_BLKSIZE has
   been inlined into its sole use.
 * The complete definition of _G_iconv_t has been moved to libio.h and
   renamed _IO_iconv_t (all actual users used that name).
 * _G_IO_IO_FILE_VERSION is vestigial; some code cares whether
   _IO_stdin_used exists, but nothing looks at its value.  I've
   preserved the value as a hardwired constant in csu/init.c.
   This means csu/init.c no longer needs to include anything.
 * Many of the headers included by _G_config.h were already being
   included directly by either either libio.h or stdio.h; the
   remaining ones were moved to libio.h.
 * _G_HAVE_MREMAP is still relevant, because mremap genuinely is a
   Linux extension; it's not in POSIX and as far as I can tell it's
   not available on the Hurd either.  I also preserved _G_HAVE_MMAP,
   since it's conceivable someone would want to port glibc to a
   MMU-less, mmap-less environment in the future.  Both are now always
   defined to 1/0 as is the current convention, instead of the older
   1/undef convention.  These are the only symbols still defined in
   _G_config.h.
 * The actual inclusion of _G_config.h moves from libio.h to libioP.h,
   as this is where a potential override of _G_HAVE_MMAP happens.
 * The #ifdef logic in libioP.h controlling _IO_JUMPS_OFFSET has been
   simplified.

After this patch, the only surviving _G_ symbols are the struct tag
names _G_fpos_t and _G_fpos64_t, which are preserved for the sake of
C++ mangled names in applications, and _G_HAVE_MMAP and _G_HAVE_MREMAP,
which do not seem worth renaming.

Installed stripped libraries are unchanged by this patch.

	* bits/_G_config.h: Move back to sysdeps/generic/_G_config.h.
	Delete all contents except for definitions of _G_HAVE_MMAP and
	_G_HAVE_MREMAP.  Add commentary explaining those two symbols.
	* sysdeps/unix/sysv/linux/bits/_G_config.h: Move back to
	sysdeps/unix/sysv/linux/_G_config.h.  Make same content
	change as above.

	* libio/libio.h: Don't include bits/_G_config.h here.
	Include stddef.h with __need_wchar_t defined.  Include
	bits/types/__mbstate_t.h, bits/types/wint_t.h, and gconv.h.
	Define _IO_iconv_t here, directly.
	Don't define _IO_HAVE_ST_BLKSIZE.
	* libio/libioP.h: Include _G_config.h here.  Move include of
	shlib-compat.h up with rest of includes.  Simplify conditionals
	controlling definition of _IO_JUMPS_OFFSET.

	* csu/init.c: Remove always-true #if around entire file.
	Don't include stdio.h.  Set _IO_stdin_used to hardwired
	constant 0x20001, and update commentary.
	* include/stdio.h, sysdeps/ieee754/ldbl-opt/nldbl-compat.h:
	Replace all uses of _G_va_list with __gnuc_va_list.
	* libio/filedoalloc.c: Use #if defined _STATBUF_ST_BLKSIZE
	instead of #if _IO_HAVE_ST_BLKSIZE.
	* libio/fileops.c: Test _G_HAVE_MREMAP with #if, not #ifdef.
	* libio/iofdopen.c, libio/iofopen.c: Test _G_HAVE_MMAP with #if,
	not #ifdef.

14 files changed, 116 insertions, 156 deletions

diff --git a/ChangeLog b/ChangeLog
index 1f661e1c56..41e870c1c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,32 @@
 2018-02-07  Zack Weinberg  <zackw@panix.com>
 
+	* bits/_G_config.h: Move back to sysdeps/generic/_G_config.h.
+	Delete all contents except for definitions of _G_HAVE_MMAP and
+	_G_HAVE_MREMAP.  Add commentary explaining those two symbols.
+	* sysdeps/unix/sysv/linux/bits/_G_config.h: Move back to
+	sysdeps/unix/sysv/linux/_G_config.h.  Make same content
+	change as above.
+
+	* libio/libio.h: Don't include bits/_G_config.h here.
+	Include stddef.h with __need_wchar_t defined.  Include
+	bits/types/__mbstate_t.h, bits/types/wint_t.h, and gconv.h.
+	Define _IO_iconv_t here, directly.
+	Don't define _IO_HAVE_ST_BLKSIZE.
+	* libio/libioP.h: Include _G_config.h here.  Move include of
+	shlib-compat.h up with rest of includes.  Simplify conditionals
+	controlling definition of _IO_JUMPS_OFFSET.
+
+	* csu/init.c: Remove always-true #if around entire file.
+	Don't include stdio.h.  Set _IO_stdin_used to hardwired
+	constant 0x20001, and update commentary.
+	* include/stdio.h, sysdeps/ieee754/ldbl-opt/nldbl-compat.h:
+	Replace all uses of _G_va_list with __gnuc_va_list.
+	* libio/filedoalloc.c: Use #if defined _STATBUF_ST_BLKSIZE
+	instead of #if _IO_HAVE_ST_BLKSIZE.
+	* libio/fileops.c: Test _G_HAVE_MREMAP with #if, not #ifdef.
+	* libio/iofdopen.c, libio/iofopen.c: Test _G_HAVE_MMAP with #if,
+	not #ifdef.
+
 	* libio/bits/libio.h: Move back to libio/libio.h and adjust
 	multiple-include guard to match.
 	Merge contents of libio/bits/libio-ldbl.h and include/libio.h
diff --git a/bits/_G_config.h b/bits/_G_config.h
deleted file mode 100644
index 8c81bc4278..0000000000
--- a/bits/_G_config.h
+++ /dev/null
@@ -1,54 +0,0 @@
-/* This file is needed by libio to define various configuration parameters.
-   These are always the same in the GNU C library.  */
-
-#ifndef _BITS_G_CONFIG_H
-#define _BITS_G_CONFIG_H 1
-
-/* Define types for libio in terms of the standard internal type names.  */
-
-#include <bits/types.h>
-#define __need_size_t
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# define __need_wchar_t
-#endif
-#define __need_NULL
-#include <stddef.h>
-
-#include <bits/types/__mbstate_t.h>
-#include <bits/types/__fpos_t.h>
-#include <bits/types/__fpos64_t.h>
-
-#define _G_fpos_t __fpos_t
-#define _G_fpos64_t __fpos64_t
-
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# include <bits/types/wint_t.h>
-#endif
-
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# include <gconv.h>
-typedef union
-{
-  struct __gconv_info __cd;
-  struct
-  {
-    struct __gconv_info __cd;
-    struct __gconv_step_data __data;
-  } __combined;
-} _G_iconv_t;
-#endif
-
-
-/* These library features are always available in the GNU C library.  */
-#define _G_va_list __gnuc_va_list
-
-#define _G_HAVE_MMAP 1
-
-#define _G_IO_IO_FILE_VERSION 0x20001
-
-/* This is defined by <bits/stat.h> if `st_blksize' exists.  */
-#define _G_HAVE_ST_BLKSIZE defined (_STATBUF_ST_BLKSIZE)
-
-#define _G_BUFSIZ 8192
-
-#endif	/* bits/_G_config.h */
diff --git a/csu/init.c b/csu/init.c
index 178063b44b..c2f978f3da 100644
--- a/csu/init.c
+++ b/csu/init.c
@@ -16,11 +16,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#if defined __GNUC__ && __GNUC__ >= 2
-
-#include <stdio.h>
-
-/* This records which stdio is linked against in the application. */
-const int _IO_stdin_used = _G_IO_IO_FILE_VERSION;
-
-#endif
+/* Vestigial libio version number.  Some code in libio checks whether
+   this symbol exists in the executable, but nothing looks at its
+   value anymore; the value it was historically set to has been
+   preserved out of an abundance of caution.  */
+const int _IO_stdin_used = 0x20001;
diff --git a/include/stdio.h b/include/stdio.h
index f12b281b4d..94bc2fdc7e 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -15,44 +15,44 @@ extern int __snprintf (char *__restrict __s, size_t __maxlen,
      __attribute__ ((__format__ (__printf__, 3, 4)));
 libc_hidden_proto (__snprintf)
 extern int __vsnprintf (char *__restrict __s, size_t __maxlen,
-			const char *__restrict __format, _G_va_list __arg)
+			const char *__restrict __format, __gnuc_va_list __arg)
      __attribute__ ((__format__ (__printf__, 3, 0)));
 extern int __vfscanf (FILE *__restrict __s,
 		      const char *__restrict __format,
-		      _G_va_list __arg)
+		      __gnuc_va_list __arg)
      __attribute__ ((__format__ (__scanf__, 2, 0)));
 libc_hidden_proto (__vfscanf)
 extern int __vscanf (const char *__restrict __format,
-		     _G_va_list __arg)
+		     __gnuc_va_list __arg)
      __attribute__ ((__format__ (__scanf__, 1, 0)));
 extern _IO_ssize_t __getline (char **__lineptr, size_t *__n,
 			      FILE *__stream) attribute_hidden;
 extern int __vsscanf (const char *__restrict __s,
 		      const char *__restrict __format,
-		      _G_va_list __arg)
+		      __gnuc_va_list __arg)
      __attribute__ ((__format__ (__scanf__, 2, 0)));
 
 extern int __sprintf_chk (char *, int, size_t, const char *, ...) __THROW;
 extern int __snprintf_chk (char *, size_t, int, size_t, const char *, ...)
      __THROW;
 extern int __vsprintf_chk (char *, int, size_t, const char *,
-			   _G_va_list) __THROW;
+			   __gnuc_va_list) __THROW;
 extern int __vsnprintf_chk (char *, size_t, int, size_t, const char *,
-			    _G_va_list) __THROW;
+			    __gnuc_va_list) __THROW;
 extern int __printf_chk (int, const char *, ...);
 extern int __fprintf_chk (FILE *, int, const char *, ...);
-extern int __vprintf_chk (int, const char *, _G_va_list);
-extern int __vfprintf_chk (FILE *, int, const char *, _G_va_list);
+extern int __vprintf_chk (int, const char *, __gnuc_va_list);
+extern int __vfprintf_chk (FILE *, int, const char *, __gnuc_va_list);
 extern char *__fgets_unlocked_chk (char *buf, size_t size, int n, FILE *fp);
 extern char *__fgets_chk (char *buf, size_t size, int n, FILE *fp);
 extern int __asprintf_chk (char **, int, const char *, ...) __THROW;
-extern int __vasprintf_chk (char **, int, const char *, _G_va_list) __THROW;
+extern int __vasprintf_chk (char **, int, const char *, __gnuc_va_list) __THROW;
 extern int __dprintf_chk (int, int, const char *, ...);
-extern int __vdprintf_chk (int, int, const char *, _G_va_list);
+extern int __vdprintf_chk (int, int, const char *, __gnuc_va_list);
 extern int __obstack_printf_chk (struct obstack *, int, const char *, ...)
      __THROW;
 extern int __obstack_vprintf_chk (struct obstack *, int, const char *,
-				  _G_va_list) __THROW;
+				  __gnuc_va_list) __THROW;
 
 extern int __isoc99_fscanf (FILE *__restrict __stream,
 			    const char *__restrict __format, ...) __wur;
@@ -61,12 +61,12 @@ extern int __isoc99_sscanf (const char *__restrict __s,
 			    const char *__restrict __format, ...) __THROW;
 extern int __isoc99_vfscanf (FILE *__restrict __s,
 			     const char *__restrict __format,
-			     _G_va_list __arg) __wur;
+			     __gnuc_va_list __arg) __wur;
 extern int __isoc99_vscanf (const char *__restrict __format,
-			    _G_va_list __arg) __wur;
+			    __gnuc_va_list __arg) __wur;
 extern int __isoc99_vsscanf (const char *__restrict __s,
 			     const char *__restrict __format,
-			     _G_va_list __arg) __THROW;
+			     __gnuc_va_list __arg) __THROW;
 libc_hidden_proto (__isoc99_vsscanf)
 libc_hidden_proto (__isoc99_vfscanf)
 
diff --git a/libio/filedoalloc.c b/libio/filedoalloc.c
index 329843827f..d6517e493b 100644
--- a/libio/filedoalloc.c
+++ b/libio/filedoalloc.c
@@ -93,7 +93,7 @@ _IO_file_doallocate (_IO_FILE *fp)
 	      local_isatty (fp->_fileno))
 	    fp->_flags |= _IO_LINE_BUF;
 	}
-#if _IO_HAVE_ST_BLKSIZE
+#if defined _STATBUF_ST_BLKSIZE
       if (st.st_blksize > 0 && st.st_blksize < _IO_BUFSIZ)
 	size = st.st_blksize;
 #endif
diff --git a/libio/fileops.c b/libio/fileops.c
index 6d5393cea3..5fd8a9647f 100644
--- a/libio/fileops.c
+++ b/libio/fileops.c
@@ -582,7 +582,7 @@ mmap_remap_check (_IO_FILE *fp)
 	{
 	  /* The file added some pages.  We need to remap it.  */
 	  void *p;
-#ifdef _G_HAVE_MREMAP
+#if _G_HAVE_MREMAP
 	  p = __mremap (fp->_IO_buf_base, ROUNDED (fp->_IO_buf_end
 						   - fp->_IO_buf_base),
 			ROUNDED (st.st_size), MREMAP_MAYMOVE);
diff --git a/libio/iofdopen.c b/libio/iofdopen.c
index 3546d52b4d..b6f1500dee 100644
--- a/libio/iofdopen.c
+++ b/libio/iofdopen.c
@@ -126,13 +126,13 @@ _IO_new_fdopen (int fd, const char *mode)
   new_f->fp.file._lock = &new_f->lock;
 #endif
   _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd,
-#ifdef _G_HAVE_MMAP
+#if _G_HAVE_MMAP
 	       (use_mmap && (read_write & _IO_NO_WRITES))
 	       ? &_IO_wfile_jumps_maybe_mmap :
 #endif
 	       &_IO_wfile_jumps);
   _IO_JUMPS (&new_f->fp) =
-#ifdef _G_HAVE_MMAP
+#if _G_HAVE_MMAP
     (use_mmap && (read_write & _IO_NO_WRITES)) ? &_IO_file_jumps_maybe_mmap :
 #endif
       &_IO_file_jumps;
diff --git a/libio/iofopen.c b/libio/iofopen.c
index d6f59497b4..2ea82e2091 100644
--- a/libio/iofopen.c
+++ b/libio/iofopen.c
@@ -33,7 +33,7 @@
 _IO_FILE *
 __fopen_maybe_mmap (_IO_FILE *fp)
 {
-#ifdef _G_HAVE_MMAP
+#if _G_HAVE_MMAP
   if ((fp->_flags2 & _IO_FLAGS2_MMAP) && (fp->_flags & _IO_NO_WRITES))
     {
       /* Since this is read-only, we might be able to mmap the contents
diff --git a/libio/libio.h b/libio/libio.h
index ff67e18c18..0953120247 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -41,8 +41,24 @@
 # error "Someone forgot to include stdio-lock.h"
 #endif
 
-#include <bits/_G_config.h>
-/* ALL of these should be defined in _G_config.h */
+#define __need_wchar_t
+#include <stddef.h>
+
+#include <bits/types/__mbstate_t.h>
+#include <bits/types/wint_t.h>
+#include <gconv.h>
+
+typedef union
+{
+  struct __gconv_info __cd;
+  struct
+  {
+    struct __gconv_info __cd;
+    struct __gconv_step_data __data;
+  } __combined;
+} _IO_iconv_t;
+
+/* Map the names used in libio to the names used in libc generally.  */
 #define _IO_fpos_t __fpos_t
 #define _IO_fpos64_t __fpos64_t
 #define _IO_size_t size_t
@@ -51,8 +67,6 @@
 #define _IO_off64_t __off64_t
 #define _IO_pid_t __pid_t
 #define _IO_uid_t __uid_t
-#define _IO_iconv_t _G_iconv_t
-#define _IO_HAVE_ST_BLKSIZE _G_HAVE_ST_BLKSIZE
 #define _IO_BUFSIZ BUFSIZ
 #define _IO_wint_t wint_t
 #define _IO_va_list __gnuc_va_list
diff --git a/libio/libioP.h b/libio/libioP.h
index 8edc207277..58cc9de094 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -46,6 +46,12 @@
 #include <libio/libio.h>
 #include "iolibio.h"
 
+#include <shlib-compat.h>
+
+/* For historical reasons this is the name of the sysdeps header that
+   adjusts the libio configuration.  */
+#include <_G_config.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -75,16 +81,10 @@ extern "C" {
  * object being acted on (i.e. the 'this' parameter).
  */
 
-#include <shlib-compat.h>
-#if !SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
-  /* Setting this macro disables the use of the _vtable_offset bias in
-     _IO_JUMPS_FUNCS, below.  That is only needed if we want to
-     support old binaries (see oldfileops.c).  */
-# define _G_IO_NO_BACKWARD_COMPAT 1
-#endif
-
-#if (!defined _IO_USE_OLD_IO_FILE \
-     && (!defined _G_IO_NO_BACKWARD_COMPAT || _G_IO_NO_BACKWARD_COMPAT == 0))
+/* Setting this macro to 1 enables the use of the _vtable_offset bias
+   in _IO_JUMPS_FUNCS, below.  This is only needed for new-format
+   _IO_FILE in libc that must support old binaries (see oldfileops.c).  */
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1) && !defined _IO_USE_OLD_IO_FILE
 # define _IO_JUMPS_OFFSET 1
 #else
 # define _IO_JUMPS_OFFSET 0
diff --git a/sysdeps/generic/_G_config.h b/sysdeps/generic/_G_config.h
new file mode 100644
index 0000000000..7c917bf64c
--- /dev/null
+++ b/sysdeps/generic/_G_config.h
@@ -0,0 +1,15 @@
+/* Configuration parameters for stdio - generic version.  */
+
+#ifndef __G_CONFIG_H
+#define __G_CONFIG_H 1
+
+/* Define to 1 if the operating system supports mmap, 0 otherwise.
+   This function is required by POSIX but might still be unavailable,
+   for instance when the hardware lacks support for virtual memory.  */
+#define _G_HAVE_MMAP 1
+
+/* Define to 1 if the operating system supports mremap, 0 otherwise.
+   This function is currently a Linux-specific extension.  */
+#define _G_HAVE_MREMAP 0
+
+#endif	/* _G_config.h */
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
index 3b3ef731a6..d61fbb2f64 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.h
@@ -82,22 +82,23 @@ extern ssize_t __nldbl___vstrfmon (char *, size_t, const char *, va_list)
 /* These don't use __typeof because they were not declared by the headers,
    since we don't compile with _FORTIFY_SOURCE.  */
 extern int __nldbl___vfprintf_chk (FILE *__restrict, int,
-				   const char *__restrict, _G_va_list);
+				   const char *__restrict, __gnuc_va_list);
 extern int __nldbl___vfwprintf_chk (FILE *__restrict, int,
 				    const wchar_t *__restrict, __gnuc_va_list);
 extern int __nldbl___vsprintf_chk (char *__restrict, int, size_t,
-				   const char *__restrict, _G_va_list) __THROW;
+				   const char *__restrict, __gnuc_va_list)
+  __THROW;
 extern int __nldbl___vsnprintf_chk (char *__restrict, size_t, int, size_t,
-				    const char *__restrict, _G_va_list)
+				    const char *__restrict, __gnuc_va_list)
   __THROW;
 extern int __nldbl___vswprintf_chk (wchar_t *__restrict, size_t, int, size_t,
 				    const wchar_t *__restrict, __gnuc_va_list)
   __THROW;
-extern int __nldbl___vasprintf_chk (char **, int, const char *, _G_va_list)
+extern int __nldbl___vasprintf_chk (char **, int, const char *, __gnuc_va_list)
   __THROW;
-extern int __nldbl___vdprintf_chk (int, int, const char *, _G_va_list);
+extern int __nldbl___vdprintf_chk (int, int, const char *, __gnuc_va_list);
 extern int __nldbl___obstack_vprintf_chk (struct obstack *, int, const char *,
-					  _G_va_list) __THROW;
+					  __gnuc_va_list) __THROW;
 extern void __nldbl___vsyslog_chk (int, int, const char *, va_list);
 
 
diff --git a/sysdeps/unix/sysv/linux/_G_config.h b/sysdeps/unix/sysv/linux/_G_config.h
new file mode 100644
index 0000000000..0413716481
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/_G_config.h
@@ -0,0 +1,15 @@
+/* Configuration parameters for stdio - Linux version.  */
+
+#ifndef __G_CONFIG_H
+#define __G_CONFIG_H 1
+
+/* Define to 1 if the operating system supports mmap, 0 otherwise.
+   This function is required by POSIX but might still be unavailable,
+   for instance when the hardware lacks support for virtual memory.  */
+#define _G_HAVE_MMAP 1
+
+/* Define to 1 if the operating system supports mremap, 0 otherwise.
+   This function is currently a Linux-specific extension.  */
+#define _G_HAVE_MREMAP 1
+
+#endif	/* bits/_G_config.h */
diff --git a/sysdeps/unix/sysv/linux/bits/_G_config.h b/sysdeps/unix/sysv/linux/bits/_G_config.h
deleted file mode 100644
index 05a64acb2c..0000000000
--- a/sysdeps/unix/sysv/linux/bits/_G_config.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/* This file is needed by libio to define various configuration parameters.
-   These are always the same in the GNU C library.  */
-
-#ifndef _BITS_G_CONFIG_H
-#define _BITS_G_CONFIG_H 1
-
-/* Define types for libio in terms of the standard internal type names.  */
-
-#include <bits/types.h>
-#define __need_size_t
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# define __need_wchar_t
-#endif
-#define __need_NULL
-#include <stddef.h>
-
-#include <bits/types/__mbstate_t.h>
-#include <bits/types/__fpos_t.h>
-#include <bits/types/__fpos64_t.h>
-
-#define _G_fpos_t __fpos_t
-#define _G_fpos64_t __fpos64_t
-
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# include <bits/types/wint_t.h>
-#endif
-
-#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
-# include <gconv.h>
-typedef union
-{
-  struct __gconv_info __cd;
-  struct
-  {
-    struct __gconv_info __cd;
-    struct __gconv_step_data __data;
-  } __combined;
-} _G_iconv_t;
-#endif
-
-
-/* These library features are always available in the GNU C library.  */
-#define _G_va_list __gnuc_va_list
-
-#define _G_HAVE_MMAP 1
-#define _G_HAVE_MREMAP 1
-
-#define _G_IO_IO_FILE_VERSION 0x20001
-
-/* This is defined by <bits/stat.h> if `st_blksize' exists.  */
-#define _G_HAVE_ST_BLKSIZE defined (_STATBUF_ST_BLKSIZE)
-
-#define _G_BUFSIZ 8192
-
-#endif	/* bits/_G_config.h */