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* [Bug c/53369] New: Integral promotion with ~ operator - Different behavior for signed and unsigned char.
@ 2012-05-16 0:04 rahulnitk2004 at gmail dot com
2012-05-16 0:05 ` [Bug c/53369] " rahulnitk2004 at gmail dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: rahulnitk2004 at gmail dot com @ 2012-05-16 0:04 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53369
Bug #: 53369
Summary: Integral promotion with ~ operator - Different
behavior for signed and unsigned char.
Classification: Unclassified
Product: gcc
Version: 4.5.2
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: rahulnitk2004@gmail.com
Created attachment 27413
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27413
The preprocessed file
I face a problem when i use bitwise ~ operator on signed char. With unsigned
char, it works as per the K&R ANSI C specification.
Here is the code snippet.
signed char a = 1 << 7;
unsigned char b = 1 << 7;
printf("%hd %hu\n", ~a, ~b);
Output for the program is shown as: 127 65407.
As per the integral promotion concept, a char variable whether signed or
unsigned will be converted to int before performing an operation on it.
So before performing (~a), a will be converted to int and will have 32 bits
(In my machine int is 32 bit). So ~a should result in 0XFFFFFF7F. So when i
print ~a it should result in 0XFF7F as format specifier is "%hd". Instead it is
only 127(0X7F).
Similarly for unsigned char b, ~b should result in 0XFFFFFF7F and output should
be 65407(0XFF7F) as i used "%hu" as format specifier. That is printed
correctly.
I am using GCC version 4.5.2 on Ubuntu.
Any suggestions?
Thanks
Rahul
---------------------------------------------------------------------------
Code:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
signed char a = 1 << 7;
unsigned char b = 1 << 7;
printf("%hd %hu\n", ~a, ~b);
return(EXIT_SUCCESS);
}
Compilation command used: gcc -Wall test.c (No warnings).
Output: 127 65407
------------------------------------------------------------------------------
Other Deatils:
------------------------------------------------------------------------------
rahul@ubuntu:~/sample$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.5.2-8ubuntu4' --with-bugurl=file:///usr/share/doc/gcc-4.5/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.5 --enable-shared --enable-multiarch
--with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib/x86_64-linux-gnu
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.5 --libdir=/usr/lib/x86_64-linux-gnu
--enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-gold --enable-ld=default
--with-plugin-ld=ld.gold --enable-objc-gc --disable-werror --with-arch-32=i686
--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 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu4)
------------------------------------------------------------------------------
rahul@ubuntu:~/sample$ gcc -v -save-temps -Wall test.c
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.5.2-8ubuntu4' --with-bugurl=file:///usr/share/doc/gcc-4.5/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.5 --enable-shared --enable-multiarch
--with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib/x86_64-linux-gnu
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.5 --libdir=/usr/lib/x86_64-linux-gnu
--enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-gold --enable-ld=default
--with-plugin-ld=ld.gold --enable-objc-gc --disable-werror --with-arch-32=i686
--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 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu4)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-mtune=generic' '-march=x86-64'
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/cc1 -E -quiet -v test.c
-D_FORTIFY_SOURCE=2 -mtune=generic -march=x86-64 -Wall -fpch-preprocess
-fstack-protector -o test.i
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-mtune=generic' '-march=x86-64'
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/cc1 -fpreprocessed test.i
-quiet -dumpbase test.c -mtune=generic -march=x86-64 -auxbase test -Wall
-version -fstack-protector -o test.s
GNU C (Ubuntu/Linaro 4.5.2-8ubuntu4) version 4.5.2 (x86_64-linux-gnu)
compiled by GNU C version 4.5.2, GMP version 4.3.2, MPFR version 3.0.0-p8,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C (Ubuntu/Linaro 4.5.2-8ubuntu4) version 4.5.2 (x86_64-linux-gnu)
compiled by GNU C version 4.5.2, GMP version 4.3.2, MPFR version 3.0.0-p8,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 9755ab75799195519479ef699703b13b
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-mtune=generic' '-march=x86-64'
as -V -Qy --64 -o test.o test.s
GNU assembler version 2.21.0 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.21.0.20110327
COMPILER_PATH=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/:/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/:/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/:/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/:/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/:/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../../:/lib/:/usr/lib/:/usr/lib/x86_64-linux-gnu/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-mtune=generic' '-march=x86-64'
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/collect2 --build-id
--eh-frame-hdr -m elf_x86_64 --hash-style=gnu -dynamic-linker
/lib64/ld-linux-x86-64.so.2 -z relro
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../../crt1.o
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../../crti.o
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/crtbegin.o
-L/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2
-L/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../..
-L/usr/lib/x86_64-linux-gnu test.o -lgcc --as-needed -lgcc_s --no-as-needed -lc
-lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/crtend.o
/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.5.2/../../../crtn.o
-------------------------------------------------------------------------------
^ permalink raw reply [flat|nested] 5+ messages in thread
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2012-05-16 0:04 [Bug c/53369] New: Integral promotion with ~ operator - Different behavior for signed and unsigned char rahulnitk2004 at gmail dot com
2012-05-16 0:05 ` [Bug c/53369] " rahulnitk2004 at gmail dot com
2012-05-16 0:12 ` rahulnitk2004 at gmail dot com
2012-05-16 1:39 ` pinskia at gcc dot gnu.org
2012-05-16 9:12 ` rahulnitk2004 at gmail dot com
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