symbol bloat for fortify warnings

[Roland McGrath <roland at redhat dot com>]

I really dislike the addition of symbols in the dynamic symbol table, and
in the ABI we will maintain permanently, just as a kludge for emitting
link-time warnings.  We can get the warnings done just with stuff in
libc_nonshared.a, and not suffer this bloat.

I propose the following approach instead.  This works now to produce linker
warnings.  When gcc is hopefully soon extended to support an attribute like
`deprecated' but with supplied message text, it can be:

#define __warndecl(name, msg) \
  static __inline__ __attribute__ ((__always_inline__, __warning__ (msg))) \
  void name (void) { }

to get better warnings at compile-time and produce no run-time overhead at all.

Ok?


Thanks,
Roland


2005-02-24  Roland McGrath  <roland@redhat.com>

	* debug/Versions (libc: GLIBC_2.4): Remove
	__memset_zero_constant_len_parameter.
	* sysdeps/generic/memset_chk.c: Remove alias and warning.
	* misc/sys/cdefs.h (__warndecl): New macro.
	* debug/warning-nop.c: New file.
	* string/bits/string3.h (memset): Call __warn_memset_zero_len with no
	arguments, instead of calling __memset_zero_constant_len_parameter.
	Use __warndecl for __warn_memset_zero_len.
	* debug/Makefile (routines): Add $(static-only-routines).
	(static-only-routines): New variable.

Index: misc/sys/cdefs.h
===================================================================
RCS file: /cvs/glibc/libc/misc/sys/cdefs.h,v
retrieving revision 1.61
diff -B -b -p -u -r1.61 cdefs.h
--- misc/sys/cdefs.h	7 Jan 2005 19:39:28 -0000	1.61
+++ misc/sys/cdefs.h	25 Feb 2005 02:46:07 -0000
@@ -130,6 +130,7 @@
 /* Fortify support.  */
 #define __bos(ptr) __builtin_object_size (ptr, __USE_FORTIFY_LEVEL > 1)
 #define __bos0(ptr) __builtin_object_size (ptr, 0)
+#define __warndecl(name, msg) extern void name (void)
 
 
 /* Support for flexible arrays.  */
Index: string/bits/string3.h
===================================================================
RCS file: /cvs/glibc/libc/string/bits/string3.h,v
retrieving revision 1.2
diff -B -b -p -u -r1.2 string3.h
--- string/bits/string3.h	21 Feb 2005 23:04:07 -0000	1.2
+++ string/bits/string3.h	25 Feb 2005 02:46:07 -0000
@@ -85,11 +85,11 @@ __mempcpy_ichk (void *__restrict __dest,
    especially problematic if the intended fill value is zero.  In this
    case no work is done at all.  We detect these problems by referring
    non-existing functions.  */
-extern char *__memset_zero_constant_len_parameter (void *, int, size_t,
-						   size_t);
+__warndecl (__warn_memset_zero_len,
+	    "memset used with constant zero length parameter; this could be due to transposed parameters");
 #define memset(dest, ch, len) \
   (__builtin_constant_p (len) && (len) == 0				      \
-   ? __memset_zero_constant_len_parameter (dest, ch, len, 0)		      \
+   ? (__warn_memset_zero_len (), (void) (ch), (void) (len), (void *) (dest))  \
    : ((__bos0 (dest) != (size_t) -1)					      \
       ? __builtin___memset_chk (dest, ch, len, __bos0 (dest))		      \
       : __memset_ichk (dest, ch, len)))
Index: debug/warning-nop.c
===================================================================
RCS file: debug/warning-nop.c
diff -N debug/warning-nop.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ debug/warning-nop.c	25 Feb 2005 02:46:07 -0000
@@ -0,0 +1,38 @@
+/* Dummy nop functions to elicit link-time warnings.
+   Copyright (C) 2005 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
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <sys/cdefs.h>
+
+void __nop (void)
+{
+}
+
+/* Don't insert any other #include's before this #undef!  */
+
+#undef __warndecl
+#define __warndecl(name, msg) \
+  strong_alias (__nop, name) link_warning (name, msg)
+
+#undef	__USE_FORTIFY_LEVEL
+#define __USE_FORTIFY_LEVEL 99
+
+/* Following here we need an #include for each public header file
+   that uses __warndecl.  */
+
+#include <string.h>
Index: debug/Makefile
===================================================================
RCS file: /cvs/glibc/libc/debug/Makefile,v
retrieving revision 1.23
diff -B -b -p -u -r1.23 Makefile
--- debug/Makefile	21 Feb 2005 23:08:04 -0000	1.23
+++ debug/Makefile	25 Feb 2005 02:46:07 -0000
@@ -24,14 +24,16 @@ subdir	:= debug
 headers	:= execinfo.h
 distribute = sigcontextinfo.h register-dump.h frame.h
 
-routines := backtrace backtracesyms backtracesymsfd noophooks \
+routines  = backtrace backtracesyms backtracesymsfd noophooks \
 	    memcpy_chk memmove_chk mempcpy_chk memset_chk stpcpy_chk \
 	    strcat_chk strcpy_chk strncat_chk strncpy_chk \
 	    sprintf_chk vsprintf_chk snprintf_chk vsnprintf_chk \
 	    printf_chk fprintf_chk vprintf_chk vfprintf_chk \
 	    gets_chk chk_fail readonly-area fgets_chk fgets_u_chk \
 	    read_chk pread_chk pread64_chk recv_chk recvfrom_chk \
-	    readlink_chk getwd_chk getcwd_chk
+	    readlink_chk getwd_chk getcwd_chk \
+	    $(static-only-routines)
+static-only-routines := warning-nop
 
 CFLAGS-backtrace.c = -fno-omit-frame-pointer
 CFLAGS-sprintf_chk.c = -D_IO_MTSAFE_IO
Index: debug/Versions
===================================================================
RCS file: /cvs/glibc/libc/debug/Versions,v
retrieving revision 1.5
diff -B -b -p -u -r1.5 Versions
--- debug/Versions	21 Feb 2005 23:06:50 -0000	1.5
+++ debug/Versions	25 Feb 2005 02:46:07 -0000
@@ -22,7 +22,6 @@ libc {
     __fgets_chk; __fgets_unlocked_chk;
     __read_chk; __pread_chk; __pread64_chk;
     __readlink_chk; __getcwd_chk; __getwd_chk;
-    __memset_zero_constant_len_parameter;
     __recv_chk; __recvfrom_chk;
   }
 }
Index: sysdeps/generic/memset_chk.c
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/generic/memset_chk.c,v
retrieving revision 1.2
diff -B -b -p -u -r1.2 memset_chk.c
--- sysdeps/generic/memset_chk.c	21 Feb 2005 23:05:43 -0000	1.2
+++ sysdeps/generic/memset_chk.c	25 Feb 2005 02:46:07 -0000
@@ -90,7 +90,3 @@ __memset_chk (dstpp, c, len, dstlen)
 
   return dstpp;
 }
-strong_alias (__memset_chk, __memset_zero_constant_len_parameter)
-
-link_warning (__memset_zero_constant_len_parameter,
-	      "memset used with constant zero length parameter; this could be due to transposed parameters")