Bug 16684 - [3.4 Regression] GCC should not warn about redundant redeclarations of built-ins
Summary: [3.4 Regression] GCC should not warn about redundant redeclarations of built-ins
Alias: None
Product: gcc
Classification: Unclassified
Component: c (show other bugs)
Version: 3.4.2
: P3 minor
Target Milestone: 3.4.2
Assignee: Zack Weinberg
Keywords: diagnostic
Depends on:
Reported: 2004-07-23 03:26 UTC by Alexander Kabaev
Modified: 2005-02-09 02:18 UTC (History)
2 users (show)

See Also:
Host: x86_64-portbld-freebsd5.2
Target: x86_64-portbld-freebsd5.2
Build: x86_64-portbld-freebsd5.2
Known to work: 3.3.3 3.4.2 4.0.0
Known to fail: 3.4.0 3.4.1
Last reconfirmed: 2004-07-25 04:00:17

pr16684.diff (664 bytes, patch)
2004-07-24 19:06 UTC, Zack Weinberg
Details | Diff

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Description Alexander Kabaev 2004-07-23 03:26:07 UTC

	Every built-in function is expected to have a matching prototype
	in at least one header file and completely matching prototypes are
	something that _should_ happen. Therefore, warning about that probably
	does not serve any useful purpose but only generates an unwanted noice.

System: FreeBSD k8.dnsalias.net 5.2-CURRENT FreeBSD 5.2-CURRENT #0: Mon Jul 12 00:28:33 EDT 2004 kan@k8.dnsalias.net:/usr/src/sys/amd64/compile/KAN amd64

	<machine, os, target, libraries (multiple lines)>
host: x86_64-portbld-freebsd5.2
build: x86_64-portbld-freebsd5.2
target: x86_64-portbld-freebsd5.2
configured with: ./..//gcc-3.4-20040709/configure --disable-nls --with-system-zlib --with-libiconv-prefix=/usr/local --program-suffix=34 --with-gxx-include-dir=/usr/local/lib/gcc/x86_64-portbld-freebsd5.2/3.4.2/include/c++/ --disable-shared --disable-libgcj --prefix=/usr/local x86_64-portbld-freebsd5.2

Simplified test case for amd64 (replace long long with  int for i386):

% cat test.c
void * malloc(unsigned long long size);

% gcc34 -save-temps -Wredundant-decls -c test.c
test.c:1: warning: redundant redeclaration of 'malloc'
Comment 1 Alexander Kabaev 2004-07-23 03:26:07 UTC

	Disable warning if built-in function declaration is being redeclared
	by normal declaration in user source files. 
Index: c-decl.c
RCS file: /usr/download/ncvs/src/contrib/gcc/c-decl.c,v
retrieving revision
diff -u -r1.1.1.18 c-decl.c
--- c-decl.c	21 Jun 2004 23:47:45 -0000
+++ c-decl.c	22 Jul 2004 01:55:22 -0000
@@ -1253,6 +1255,9 @@
 	 definition.  */
       && !(TREE_CODE (newdecl) == FUNCTION_DECL
 	   && DECL_INITIAL (newdecl) && !DECL_INITIAL (olddecl))
+      /* Don't warn about redundant redeclarations of builtins. */
+      && !(TREE_CODE (newdecl) == FUNCTION_DECL
+	   && !DECL_BUILT_IN (newdecl) && DECL_BUILT_IN (olddecl))
       /* Don't warn about an extern followed by a definition.  */
       && !(DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl))
       /* Don't warn about forward parameter decls.  */
Comment 2 Andrew Pinski 2004-07-23 03:34:49 UTC
: Search converges between 2004-01-01-trunk (#437) and 2004-01-17-trunk (#438).

Confirmed, a regression from 3.3.3.
Caused most likely by:
2004-01-10  Zack Weinberg  <zack@codesourcery.com>

        * c-decl.c (duplicate_decls): Break apart into...
        (diagnose_arglist_conflict, validate_proto_after_old_defn)
        (locate_old_defn, diagnose_mismatched_decls, merge_decls):
        ... these new functions.  Restructure for comprehensibility.
        Remove various archaic special cases.  Always report the
        location of the previous declaration when a diagnostic is issued.
        (redeclaration_error_message): Fold into diagnose_mismatched_decls.
        (match_builtin_function_types): Delete unnecessary forward declaration.

patches as usually goto gcc-patches@gcc.gnu.org.
Comment 3 Zack Weinberg 2004-07-24 19:06:07 UTC
Subject: Re: (PR 16684) Patch to disable warning about redundant
 redeclaration of builtin

Alexander Kabaev <kan@freebsd.org> writes:

> I tried to describe the problem in bug c/16684 titled "[3.4/3.5
> Regression] GCC should not warn about redundant redeclarations of
> built-ins". The patch below suppresses the warning if redundant
> declaration matches builtin function type exactly. The patch is
> against gcc 3.4 branch.

I am testing the following slight revision against mainline, and will
apply it there if successful.  Since it's a regression, I will also
test and apply to 3.4 branch, but only if mainline is happy.


Comment 4 Zack Weinberg 2004-07-24 19:06:09 UTC
Created attachment 6819 [details]
Comment 5 Zack Weinberg 2004-07-24 19:06:59 UTC
Comment on attachment 6819 [details]

... fix mime type ...
Comment 6 CVS Commits 2004-07-25 03:58:53 UTC
Subject: Bug 16684

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	zack@gcc.gnu.org	2004-07-25 03:58:51

Modified files:
	gcc            : ChangeLog c-decl.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg: Wredundant-decls-1.c 

Log message:
	2004-07-24  Alexander Kabaev  <kan@freebsd.org>
	Zack Weinberg  <zack@codesourcery.com
	PR 16684
	* c-decl.c (diagnose_mismatched_decls): Don't issue a
	redundant-declaration warning the first time a builtin is
	declared explicitly.
	* gcc.dg/Wredundant-decls-1.c: New test case.


Comment 7 Zack Weinberg 2004-07-25 04:00:17 UTC
fixed in 3.5 now.  will commit for 3.4 shortly.
Comment 8 Zack Weinberg 2004-07-25 04:00:51 UTC
grar stupid new/assigned thing never works the way i think it does.
Comment 9 Zack Weinberg 2004-07-25 04:24:15 UTC
3.4 branch commit message seems to have gone off into the weeds.  Oh well.
It's in now.