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* [Bug c/67764] New: -Wconversion generates false warnings for bitmask+cast expressions
@ 2015-09-29 13:21 marcin.slusarz at intel dot com
  2015-09-29 19:57 ` [Bug c/67764] " egall at gwmail dot gwu.edu
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: marcin.slusarz at intel dot com @ 2015-09-29 13:21 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67764

            Bug ID: 67764
           Summary: -Wconversion generates false warnings for bitmask+cast
                    expressions
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marcin.slusarz at intel dot com
  Target Milestone: ---

void _setbit(unsigned char *b, unsigned int i)
{
        b[i / 8] |= (unsigned char)(1 << (i % 8));
}
void _setbit_works(unsigned char *b, unsigned int i)
{
        unsigned char ii = (unsigned char)(1 << (i % 8));
        b[i / 8] |= ii;
}

void _mask_stupid(unsigned char *b, unsigned int i)
{
        b[i] |= (unsigned char)i;
}

void _mask_stupid_works(unsigned char *b, unsigned int i)
{
        unsigned char ii = (unsigned char)i;
        b[i] |= ii;
}

$ gcc -c conversion_bug.c -Wconversion -o /dev/null

generates:

conversion_bug.c: In function ‘_setbit’:
conversion_bug.c:3:21: warning: conversion to ‘unsigned char’ from ‘int’ may
alter its value [-Wconversion]
         b[i / 8] |= (unsigned char)(1 << (i % 8));
                     ^
conversion_bug.c: In function ‘_mask_stupid’:
conversion_bug.c:13:17: warning: conversion to ‘unsigned char’ from ‘int’ may
alter its value [-Wconversion]
         b[i] |= (unsigned char)i;
                 ^


gcc-4.9.3 does *not* generate this warning, while gcc-5.2.1 does.


gcc -v:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 5.2.1-17'
--with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 5.2.1 20150911 (Debian 5.2.1-17)
>From gcc-bugs-return-498305-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Tue Sep 29 13:32:28 2015
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug testsuite/67583] libstdc++-v3/testsuite/27_io/basic_stringbuf/seekoff/char/1.cc:92 erroneous call to sputn
Date: Tue, 29 Sep 2015 13:32:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg583

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Tue Sep 29 13:31:51 2015
New Revision: 228245

URL: https://gcc.gnu.org/viewcvs?rev"8245&root=gcc&view=rev
Log:
PR libstdc++/67583 Fix invalid sputn calls in tests

        PR libstdc++/67583
        * testsuite/27_io/basic_stringbuf/seekoff/char/1.cc: Fix sputn call
        with mismatched arguments.
        * testsuite/27_io/basic_stringbuf/seekoff/wchar_t/1.cc: Likewise.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/testsuite/27_io/basic_stringbuf/seekoff/char/1.cc
    trunk/libstdc++-v3/testsuite/27_io/basic_stringbuf/seekoff/wchar_t/1.cc


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end of thread, other threads:[~2015-10-01  4:07 UTC | newest]

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-- links below jump to the message on this page --
2015-09-29 13:21 [Bug c/67764] New: -Wconversion generates false warnings for bitmask+cast expressions marcin.slusarz at intel dot com
2015-09-29 19:57 ` [Bug c/67764] " egall at gwmail dot gwu.edu
2015-09-30  8:41 ` marcin.slusarz at intel dot com
2015-10-01  4:07 ` egall at gwmail dot gwu.edu

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