[Bug c++/11512] New: Wrong warning in trivial function template

[Bug c++/11512] New: Wrong warning in trivial function template

[jan at etpmod dot phys dot tue dot nl]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512

           Summary: Wrong warning in trivial function template
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jan at etpmod dot phys dot tue dot nl
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: linux, glibc-2.2.5
  GCC host triplet: linux, glibc-2.2.5
GCC target triplet: linux, glibc-2.2.5

Consider the following code. When compiling with -Wall it generates: 
 
comma.cpp: In function `int foo2()': 
comma.cpp:15: warning: left-hand operand of comma expression has no effect 
 
The 'identical' template-less function (foo1) compiles without warnings. Obviously this warning 
is wrong, and both versions of the code give the expected result. 
 
#include <cassert> 
 
int foo1() 
{ 
        int r=0; 
        for (int i=0; i<1; ++i, ++r) 
                ; 
        return r; 
} 
 
template <class T> 
int foo2() 
{ 
        int r=0; 
        for (int i=0; i<1; ++i, ++r) 
                ; 
        return r; 
} 
 
int main() 
{ 
        assert(foo1()==1); 
        assert(foo2<int>()==1); 
        return 0; 
}

[Bug c++/11512] [3.4 Regression]Wrong warning in trivial function template

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
 GCC target triplet|linux, glibc-2.2.5          |*-*-*
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2003-07-13 14:32:40
               date|                            |
            Summary|Wrong warning in trivial    |[3.4 Regression]Wrong
                   |function template           |warning in trivial function
                   |                            |template


------- Additional Comments From pinskia at physics dot uc dot edu  2003-07-13 14:32 -------
I can confirm this on the mainline (20030711).  It does not warn in 3.3.1 (20030707).
>From Phil Regression hunter: Search converges between 2003-04-11-trunk (#205) and 
2003-04-12-trunk (#206) .

[Bug c++/11512] [3.4 Regression]Wrong warning in trivial function template

[nathan at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


nathan at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |nathan at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED

[Bug c++/11512] [3.4 Regression]Wrong warning in trivial function template

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |weiss at sztaki dot hu


------- Additional Comments From pinskia at physics dot uc dot edu  2003-07-26 23:26 -------
*** Bug 11677 has been marked as a duplicate of this bug. ***

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org


------- Additional Comments From pinskia at physics dot uc dot edu  2003-08-06 14:46 -------
*** Bug 11833 has been marked as a duplicate of this bug. ***

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[3.4 Regression]Wrong       |[3.4 Regression] Spurious
                   |warning in trivial function |warning for comma-operator
                   |template                    |in templates


------- Additional Comments From pinskia at physics dot uc dot edu  2003-08-06 14:46 -------
Fix summary so that people will not file dups of this one.

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[janis187 at us dot ibm dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


janis187 at us dot ibm dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmitchel at gcc dot gnu dot
                   |                            |org


------- Additional Comments From janis187 at us dot ibm dot com  2003-08-06 23:30 -------
The regression in PR 11512 was introduced or exposed by this patch:

--- gcc/gcc/ChangeLog ---

2003-07-08  Mark Mitchell  <mark@codesourcery.com>

        * fold-const.c (make_range): Do not access operand 1 for a
        zero-operand operator.

--- gcc/gcc/cp/ChangeLog ---

2003-07-08  Mark Mitchell  <mark@codesourcery.com>

        * cp-tree.def (NON_DEPENDENT_EXPR): New node.
        * cp-tree.h (build_call_from_tree): Remove.
        (build_member_call): Likewise.
        [lots more]

At least, that's what my regression hunt came up with on
i686-pc-linux-gnu using the submitter's test case with -Wall, but it
doesn't fit with the date range that Andrew reported in comment #1.
If this looks inconsistent, let me know and I'll test a series of
compilers to see if it's an intermittent bug.

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512



------- Additional Comments From pinskia at physics dot uc dot edu  2003-08-06 23:42 -------
With Phil's regression hunter today, I now get: Search converges between 2003-07-08-trunk 
(#337) and 2003-07-09-trunk (#338). which corresponds to what Janis gets but I also tried with 
limiting to just between 2003-04-11 and 2003-04-12 it returns it fails so something is wrong 
because there is no warning at all; I do not know if it is Phil's regression hunter or gcc just rejected 
this at that point.

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gerald at pfeifer dot com


------- Additional Comments From pinskia at gcc dot gnu dot org  2003-08-16 12:43 -------
*** Bug 11945 has been marked as a duplicate of this bug. ***

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[nathan at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512


nathan at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


------- Additional Comments From nathan at gcc dot gnu dot org  2003-08-16 13:31 -------
2003-08-16  Nathan Sidwell  <nathan@codesourcery.com>

	PR c++/11512
	* stmt.c (expand_expr_stmt_value): Don't warn about any void
	typed expression.

2003-08-16  Nathan Sidwell  <nathan@codesourcery.com>

	PR c++/11512
	* cvt.c (convert_to_void): Indicate which side of conditional has
	no effects, and rhs of comma operator. Test for no sideeffect
	expressions here and always build a convert expr.
	* init.c (expand_default_init): Convert the init to void.
	* typeck.c (build_x_compound_expr): Do not check for side effects
	here.
	(build_compound_expr): Do not convert lhs when building a
	template.

[Bug c++/11512] [3.4 Regression] Spurious warning for comma-operator in templates

[cvs-commit at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11512



------- Additional Comments From cvs-commit at gcc dot gnu dot org  2003-08-16 13:32 -------
Subject: Bug 11512

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	nathan@gcc.gnu.org	2003-08-16 13:32:12

Modified files:
	gcc            : stmt.c ChangeLog 
	gcc/cp         : ChangeLog cvt.c init.c typeck.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/template: warn1.C 

Log message:
	PR c++/11512
	* stmt.c (expand_expr_stmt_value): Don't warn about any void
	typed expression.
	cp:
	PR c++/11512
	* cvt.c (convert_to_void): Indicate which side of conditional has
	no effects, and rhs of comma operator. Test for no sideeffect
	expressions here and always build a convert expr.
	* init.c (expand_default_init): Convert the init to void.
	* typeck.c (build_x_compound_expr): Do not check for side effects
	here.
	(build_compound_expr): Do not convert lhs when building a
	template.
	testsuite:
	PR C++/11512
	* g++.dg/template/warn1.C: New.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/stmt.c.diff?cvsroot=gcc&r1=1.324&r2=1.325
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.787&r2=2.788
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.3603&r2=1.3604
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cvt.c.diff?cvsroot=gcc&r1=1.143&r2=1.144
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/init.c.diff?cvsroot=gcc&r1=1.337&r2=1.338
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&r1=1.492&r2=1.493
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.2972&r2=1.2973
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/warn1.C.diff?cvsroot=gcc&r1=NONE&r2=1.1