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* [Bug libc/12373] New: FD_SET macro gives warning with -Wconversion (with solution)
@ 2011-01-07 9:11 johan162 at gmail dot com
2011-01-10 3:18 ` [Bug libc/12373] " drepper.fsp at gmail dot com
2014-06-27 14:03 ` fweimer at redhat dot com
0 siblings, 2 replies; 3+ messages in thread
From: johan162 at gmail dot com @ 2011-01-07 9:11 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=12373
Summary: FD_SET macro gives warning with -Wconversion (with
solution)
Product: glibc
Version: 2.11
Status: NEW
Severity: normal
Priority: P2
Component: libc
AssignedTo: drepper.fsp@gmail.com
ReportedBy: johan162@gmail.com
It is not possible to compile the following code with gcc 4.4.1 and extra
warnings enabled without warning
#include <sys/select.h>
int main(void)
{
fd_set fds;
int fd = 0;
FD_ZERO(&fds);
FD_SET(fd, &fds);
return 0;
}
Compiling this:
gcc -Werror -Wconversion wtst.c
cc1: warnings being treated as errors
wtst.c: In function ‘main’:
wtst.c:8: error: conversion to ‘unsigned int’ from ‘int’ may change the sign of
the result
wtst.c:8: error: conversion to ‘unsigned int’ from ‘int’ may change the sign of
the result
gcc --version
gcc (SUSE Linux) 4.4.1 [gcc-4_4-branch revision 150839]
The problem stems from the inline assmebler expansion where there is type of fd
clashes with the return type of the sizeof() operator.
This can easily be corrected by changing the macro from the existing:
__asm__ __volatile__ ("btsl %1,%0" : "=m" (((&fds)->__fds_bits)[((fd) / (8 *
sizeof (__fd_mask)))]) : "r" (((int) (fd)) % (8 * sizeof (__fd_mask))) :
"cc","memory");
to
__asm__ __volatile__ ("btsl %1,%0" : "=m"
(((&fds)->__fds_bits)[((unsigned)(fd) / (8 * sizeof (__fd_mask)))]) : "r"
(((unsigned) (fd)) % (8 * sizeof (__fd_mask))) : "cc","memory");
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* [Bug libc/12373] FD_SET macro gives warning with -Wconversion (with solution)
2011-01-07 9:11 [Bug libc/12373] New: FD_SET macro gives warning with -Wconversion (with solution) johan162 at gmail dot com
@ 2011-01-10 3:18 ` drepper.fsp at gmail dot com
2014-06-27 14:03 ` fweimer at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: drepper.fsp at gmail dot com @ 2011-01-10 3:18 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=12373
Ulrich Drepper <drepper.fsp at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |WORKSFORME
--- Comment #1 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-01-10 03:17:57 UTC ---
I cannot reproduce such a problem with gcc 4.5.1. Perhaps a gcc problem.
I nevertheless changed the code since nowadays gcc generates better code with
the generic version of the macros than with the inline asms.
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* [Bug libc/12373] FD_SET macro gives warning with -Wconversion (with solution)
2011-01-07 9:11 [Bug libc/12373] New: FD_SET macro gives warning with -Wconversion (with solution) johan162 at gmail dot com
2011-01-10 3:18 ` [Bug libc/12373] " drepper.fsp at gmail dot com
@ 2014-06-27 14:03 ` fweimer at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: fweimer at redhat dot com @ 2014-06-27 14:03 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=12373
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Flags| |security-
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end of thread, other threads:[~2014-06-27 14:03 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2011-01-07 9:11 [Bug libc/12373] New: FD_SET macro gives warning with -Wconversion (with solution) johan162 at gmail dot com
2011-01-10 3:18 ` [Bug libc/12373] " drepper.fsp at gmail dot com
2014-06-27 14:03 ` fweimer at redhat dot com
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