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: unassig...@gcc.gnu.org ReportedBy: rahulnitk2...@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 -------------------------------------------------------------------------------