[Bug c++/18514] New: Alternate "asm" name ignored for function imported into namespace std

[Bug c++/18514] New: Alternate "asm" name ignored for function imported into namespace std

[austern at apple dot com]

Compile the following test case:

extern  "C" {
  typedef unsigned long size_t;
  int snprintf(char * , size_t, const char * , ...) __asm("_fancy_snprintf");
}

namespace std { using ::snprintf; }

namespace std { void foo() { snprintf(0, 3, ""); } }

If you examine the assembly file or the .o file, you will see that we're invoking _snprintf.  This is wrong.  
We should be invoking _fancy_snprintf.

Note that it's important that we're importing into namespace std.  If I change the name to something 
else, the problem goes away.

-- 
           Summary: Alternate "asm" name ignored for function imported into
                    namespace std
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: austern at apple dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: powerpc-apple-darwin7.6.0
  GCC host triplet: powerpc-apple-darwin7.6.0
GCC target triplet: powerpc-apple-darwin7.6.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] Alternate "asm" name ignored for function imported into namespace std

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-16 04:37 -------
Confirmed on ppc-darwin but it works on x86-linux for some reason.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
  GCC build triplet|powerpc-apple-darwin7.6.0   |
   GCC host triplet|powerpc-apple-darwin7.6.0   |
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-11-16 04:37:01
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for function imported into namespace std

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-16 05:33 -------
now I understand why it works on x86-linux, size_t is defined as unsigned int and not unsigned long.


It worked in 3.3.

The problem appeared between 20030301 and 20030302.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Alternate "asm" name ignored|[3.4/4.0 Regression]
                   |for function imported into  |Alternate "asm" name ignored
                   |namespace std               |for function imported into
                   |                            |namespace std
   Target Milestone|---                         |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[neroden at gcc dot gnu dot org]

------- Additional Comments From neroden at gcc dot gnu dot org  2004-11-27 00:20 -------
In 3.4.2 (Debian's version), I can import into *any* namespace (xxx, for 
instance) and get the same "problem".  However, it *is* essential that the 
function be "snprintf", and not "bar".  fancy_snprintf is invoked if gcc is 
invoked with -fno-builtin-snprintf. 
 
So this looks like an issue with builtins; the builtin is not being overridden 
by the explicit declaration.  I believe this is semi-documented behavior, 
though I suppose it could be documented better. 
 
In 4.0.0, this indeed only happens when importing into std (otherwise 
fancy_snprintf is used).  It still must be "snprintf" rather than, for 
instance, "bar", and the problem still goes away when -fno-builtin-snprintf 
is used. 
 
So it still seems to be a problem with builtins, but for some reason 4.0 
treats importing a builtin into std differently from importing it into xxx, 
while 3.4 doesn't (so this bug should be hit *more* in 3.4). 
 
Resummarizing to note that this is strictly a builtin issue. 
 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |3.4.2 4.0.0
   Last reconfirmed|2004-11-16 04:37:01         |2004-11-27 00:20:57
               date|                            |
            Summary|[3.4/4.0 Regression]        |[3.4/4.0 Regression]
                   |Alternate "asm" name ignored|Alternate "asm" name ignored
                   |for function imported into  |for redeclared builtin
                   |namespace std               |function imported into
                   |                            |namespace std


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[austern at apple dot com]

------- Additional Comments From austern at apple dot com  2004-11-29 20:56 -------
Yep, I see what the problem is now.  When we create a builtin in C++, we create the declaration in both 
the global namespace and namespace std. Later, when we see the declaration of snprintf in the global 
namespace, we correctly set the assembler name of ::snprintf.  We don't set the assembler name of ::
snprintf, since it's a separate declaration. Then we see the using-declaration, which is handled by 
do_nonmember_using_decl. It sees that we have an snprintf in namespace std already, verifies that ::
snprintf and std::snprintf are compatible so this is not an error, and then just continues to use the 
original declaration of std::snprintf that was created by builtin_function.  Nothing ever sets the 
assembler name of std::snprintf to match the one that got set for ::snprintf.

So what to do about this? In principle, I think the answer is that builtin_function is doing something 
wrong by calling builtin_function_1 twice, once for the global namespace and once for namespace std.  
If we really must define all builtins in namespace std (what's the rationale?), then at least we should do 
it with a using-declaration instead of creating two entirely separate decls.  This would help compile 
time performance a little bit: builtin_function_1 is just expensive enough to show up on profiles.

If that's too radical a change given the current state of the compiler, then we could special-case builtins 
in do_nonmember_using_decl to make sure that the assembler name gets copied correctly. This 
wouldn't be hard.  There's already some special-casing for builtins there. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

Re: [Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[Gabriel Dos Reis]

"austern at apple dot com" <gcc-bugzilla@gcc.gnu.org> writes:

| So what to do about this? In principle, I think the answer is that
| builtin_function is doing something  wrong by calling
| builtin_function_1 twice, once for the global namespace and once for
| namespace std.  If we really must define all builtins in namespace
| std (what's the rationale?), then at least we should do it with a
| using-declaration instead of creating two entirely separate decls.
| This would help compile  

I believe what happened there is that it was an attempt to implement
the standard mandated semantics where names in <xxx.h> appears to be
using-declarations for names in <cxx> -- except that the actual
implementation gets everything wrong :-/

So the idea was that we get an artificial declaration in both :: and
std::.  If we actually write a decl in std::, that is it; same if we 
write it in ::.  Except that the artificial declaration in :: should
have been a using-declaration for the "real" artificial declaration in
std::.  And attributes and whatever should apply transparently to 
both -- because they have extern "C" language specification.  That is
what failed. 

-- Gaby

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[gdr at integrable-solutions dot net]

------- Additional Comments From gdr at integrable-solutions dot net  2004-11-30 11:46 -------
Subject: Re:  [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

"austern at apple dot com" <gcc-bugzilla@gcc.gnu.org> writes:

| So what to do about this? In principle, I think the answer is that
| builtin_function is doing something  wrong by calling
| builtin_function_1 twice, once for the global namespace and once for
| namespace std.  If we really must define all builtins in namespace
| std (what's the rationale?), then at least we should do it with a
| using-declaration instead of creating two entirely separate decls.
| This would help compile  

I believe what happened there is that it was an attempt to implement
the standard mandated semantics where names in <xxx.h> appears to be
using-declarations for names in <cxx> -- except that the actual
implementation gets everything wrong :-/

So the idea was that we get an artificial declaration in both :: and
std::.  If we actually write a decl in std::, that is it; same if we 
write it in ::.  Except that the artificial declaration in :: should
have been a using-declaration for the "real" artificial declaration in
std::.  And attributes and whatever should apply transparently to 
both -- because they have extern "C" language specification.  That is
what failed. 

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-09 00:43 -------
Patch here: <http://gcc.gnu.org/ml/gcc-patches/2004-12/msg00645.html>.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4/4.0 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-12-09 21:07 -------
Subject: Bug 18514

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	austern@gcc.gnu.org	2004-12-09 21:07:01

Modified files:
	gcc/cp         : ChangeLog name-lookup.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/ext: builtin1.C builtin2.C builtin3.C 
	                          builtin4.C builtin5.C 

Log message:
	PR c++/18514
	* name-lookup.c (do_nonmember_using_decl): A real function
	declaration takes precedence over an anticipated declaration.
	* g++.dg/ext/builtin1.C: New
	* g++.dg/ext/builtin2.C: New
	* g++.dg/ext/builtin3.C: New
	* g++.dg/ext/builtin4.C: New
	* g++.dg/ext/builtin5.C: New

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4526&r2=1.4527
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/name-lookup.c.diff?cvsroot=gcc&r1=1.100&r2=1.101
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4731&r2=1.4732
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin1.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin2.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin3.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin4.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin5.C.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-09 21:24 -------
Fixed at least on the mainline.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|3.4.2 4.0.0                 |3.4.2
      Known to work|                            |4.0.0
            Summary|[3.4/4.0 Regression]        |[3.4 Regression] Alternate
                   |Alternate "asm" name ignored|"asm" name ignored for
                   |for redeclared builtin      |redeclared builtin function
                   |function imported into      |imported into namespace std
                   |namespace std               |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-12-09 22:52 -------
Subject: Bug 18514

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	apple-ppc-branch
Changes by:	austern@gcc.gnu.org	2004-12-09 22:52:32

Modified files:
	gcc/cp         : ChangeLog name-lookup.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/ext: builtin1.C builtin2.C builtin3.C 
	                          builtin4.C builtin5.C 

Log message:
	Radar 3845695: iostream not long double savvy, but printf is
	Ported from FSF mainline, where it was a fix for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514 and reviewed by Nathan Sidwell
	Reviewed for inclusion in apple-ppc-branch by Geoff Keating and Mike Stump
	
	PR c++/18514
	* name-lookup.c (do_nonmember_using_decl): A real function
	declaration takes precedence over an anticipated declaration.
	* g++.dg/ext/builtin1.C: New
	* g++.dg/ext/builtin2.C: New
	* g++.dg/ext/builtin3.C: New
	* g++.dg/ext/builtin4.C: New
	* g++.dg/ext/builtin5.C: New

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=1.2849.2.70.2.7&r2=1.2849.2.70.2.8
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/name-lookup.c.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=1.4.2.14.2.7&r2=1.4.2.14.2.8
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=1.1936.2.54.2.12&r2=1.1936.2.54.2.13
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin1.C.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin2.C.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin3.C.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin4.C.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/ext/builtin5.C.diff?cvsroot=gcc&only_with_tag=apple-ppc-branch&r1=NONE&r2=1.1.2.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514

[Bug c++/18514] [3.4 Regression] Alternate "asm" name ignored for redeclared builtin function imported into namespace std

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18514