>Submitter-Id: net >Originator: Robert Samal >Organization: Charles University, Prague >Confidential: no >Synopsis: -O2 optimalization produces wrong code >Severity: serious >Priority: medium >Category: c >Class: wrong-code >Release: 3.0.4 (Debian testing/unstable) >Environment: System: Linux camelot 2.4.19 #1 Fri Aug 16 17:01:16 CEST 2002 i686 unknown Architecture: i686
host: i386-pc-linux-gnu build: i386-pc-linux-gnu target: i386-pc-linux-gnu configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux >Description: On the following code, gcc (version 3.0 or 3.3) with -O2 (or higer) produces wrong code from a very short program ... >How-To-Repeat: gcc -O2 the_following_file /* bug in gcc -O2 Reading specs from /usr/lib/gcc-lib/i386-linux/3.0.4/specs Configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux Thread model: posix gcc version 3.0.4 The same problem at another machine Reading specs from /usr/lib/gcc-lib/i386-linux/3.3/specs Configured with: ../src/configure -v --enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib --enable-nls --without-included-gettext --enable-__cxa_atexit --enable-clocale=gnu --enable-debug --enable-java-gc=boehm --enable-java-awt=xlib --enable-objc-gc i386-linux Thread model: posix gcc version 3.3 (Debian) **************** When compiled without optimalization, the program behaves correctly, it is it print lines upto "B f=4, l=12". However, when compiled with -O2, it finishes with " A f=1, l=3", when the inner while cycle condition is still satisfied ... Maybe the two while-cycles are somehow mixed up? */ int main() { int i; int first= 0; int last= 0; while (last<3) { last = first; while(first<=last) { first++; for (i=0;i<3;i++){ last++; printf("C f=%d, l=%d\n",first,last); } printf("B f=%d, l=%d\n",first,last); if (last>10) return 0; } printf(" A f=%d, l=%d\n",first,last); } return 0; } >Fix: Compile without optimization or with version 2.95 ... ;-)