[Bug c/59940] New: Imprecise column number for -Wconversion

[Bug c/59940] New: Imprecise column number for -Wconversion

[chengniansun at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59940

            Bug ID: 59940
           Summary: Imprecise column number for -Wconversion
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com

The column numbers of conversion warnings are not precise. 



$: cat s.c
int f(unsigned i);

int g(int i) {
return       f(i) + f(i)
                  + f(i);
}
$: gcc-trunk -c -Wconversion s.c
s.c: In function ‘g’:
s.c:4:1: warning: conversion to ‘unsigned int’ from ‘int’ may change the sign
of the result [-Wsign-conversion]
 return       f(i) + f(i)
 ^
s.c:4:1: warning: conversion to ‘unsigned int’ from ‘int’ may change the sign
of the result [-Wsign-conversion]
s.c:5:19: warning: conversion to ‘unsigned int’ from ‘int’ may change the sign
of the result [-Wsign-conversion]
                   + f(i);
                   ^
$: clang-trunk -c -Wconversion s.c
s.c:4:16: warning: implicit conversion changes signedness: 'int' to 'unsigned
int' [-Wsign-conversion]
return       f(i) + f(i)
             ~ ^
s.c:4:23: warning: implicit conversion changes signedness: 'int' to 'unsigned
int' [-Wsign-conversion]
return       f(i) + f(i)
                    ~ ^
s.c:5:23: warning: implicit conversion changes signedness: 'int' to 'unsigned
int' [-Wsign-conversion]
                  + f(i);
                    ~ ^
3 warnings generated.
$: gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/chengniansun/tools/gcc-trunk-binaries/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --enable-languages=c,c++
--disable-multilib --prefix=/home/chengniansun/tools/gcc-trunk-binaries :
(reconfigured) ../gcc-trunk/configure --enable-languages=c,c++
--disable-multilib --prefix=/home/chengniansun/tools/gcc-trunk-binaries
Thread model: posix
gcc version 4.9.0 20140123 (experimental) (GCC)
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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug bootstrap/59934] Bootstrap fail since r206941: expmed.h:252:33: error: array subscript is above array bounds
Date: Sat, 25 Jan 2014 05:01:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY934

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2014-01-25
     Ever confirmed|0                           |1

--- Comment #11 from Jeffrey A. Law <law at redhat dot com> ---
The amount of overhead is, umm, so little to be in the noise.

We end up turning one arithmetic & return/branch into 3 immediate loads and a
call on a path that's so cold it should never matter.

Your solution returns a bogus value for those conditions.  That should never
happen, but if it does, returning a value that may then be mis-interpreted/used
by the caller just seems like a problem waiting to happen.

WRT --disable-checking making the warning come back, that's easy enough to fix.
 Instead of gcc_assert, we just do make it look like an old fashioned abort:

if (cant_happen)
  abort ();

[Bug c/59940] Imprecise column number for -Wconversion

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59940

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2014-01-26
                 CC|                            |mpolacek at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |4.9.0
     Ever confirmed|0                           |1

[Bug c/59940] Imprecise column number for -Wconversion

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59940

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Thu Jan 30 16:15:36 2014
New Revision: 207309

URL: http://gcc.gnu.org/viewcvs?rev=207309&root=gcc&view=rev
Log:
    PR c/59940
c-family/
    * c-common.h (unsafe_conversion_p): Adjust declaration.
    (warnings_for_convert_and_check): Likewise.
    (convert_and_check): Likewise.
    * c-common.c (unsafe_conversion_p): Add location parameter.  Call
    expansion_point_location_if_in_system_header on it.
    (warnings_for_convert_and_check): Add location parameter.  Call
    expansion_point_location_if_in_system_header on it.  Use it.
    (convert_and_check): Add location parameter.  Use it.
    (conversion_warning): Likewise.
    (c_add_case_label): Adjust convert_and_check calls.
    (scalar_to_vector): Adjust unsafe_conversion_p calls.
cp/
    * typeck.c (build_ptrmemfunc1): Call convert_and_check with
    input_location.
    * cvt.c (cp_convert_and_check): Call warnings_for_convert_and_check
    with input_location.
    * call.c (build_conditional_expr_1): Call unsafe_conversion_p with
    loc parameter.
c/
    * c-typeck.c (build_function_call_vec): Use loc parameter.
    (convert_arguments): Add location parameter.  Use it.
    (ep_convert_and_check): Likewise.
    (build_atomic_assign): Adjust convert_for_assignment call.
    (build_modify_expr): Likewise.
    (digest_init): Likewise.
    (c_finish_return): Likewise.
    (build_conditional_expr): Adjust ep_convert_and_check calls.
    (convert_for_assignment): Add rhs_loc parameter.  Use it.
    (build_binary_op): Adjust convert_and_check and ep_convert_and_check
    calls.
testsuite/
    * gcc.dg/pr59940.c: New test.
    * gcc.dg/pr35635.c (func3): Move dg-warning.


Added:
    trunk/gcc/testsuite/gcc.dg/pr59940.c
Modified:
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-common.c
    trunk/gcc/c-family/c-common.h
    trunk/gcc/c/ChangeLog
    trunk/gcc/c/c-typeck.c
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/cvt.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/pr35635.c

[Bug c/59940] Imprecise column number for -Wconversion

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59940

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I'm marking this as FIXED, but the PR59963 fix will bring some more
improvements.