Created attachment 23131 [details] complexbug3.i This is a report about an issue encountered in MinGW GCC. The maintainers of the MinGW project suggested to report it here. The command line that triggers the bug is: gcc -v -save-temps -Wall -std=c99 complexbug3.c -o complexbug3.exe The option -std=c99 triggers the bug. The resultant output is: Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=c:/program files/mingw/bin/../libexec/gcc/mingw32/4.5.0/lto-wrapper.exe Target: mingw32 Configured with: ../gcc-4.5.0/configure --enable-languages=c,c++,ada,fortran,objc,obj-c++ --disable-sjlj-exceptions --with-dwarf2 --enable-shared --enable-libgomp --disable-win32-registry --enable-libstdcxx-debug --enable-version-specific-runtime-libs --disable-werror --build=mingw32 --prefix=/mingw Thread model: win32 gcc version 4.5.0 (GCC) COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=c99' '-o' 'complexbug3.exe' '-mtune=i386' '-march=i386' c:/program files/mingw/bin/../libexec/gcc/mingw32/4.5.0/cc1.exe -E -quiet -v -iprefix c:\program files\mingw\bin\../lib/gcc/mingw32/4.5.0/ complexbug3.c -mtune=i386 -march=i386 -std=c99 -Wall -fpch-preprocess -o complexbug3.i ignoring nonexistent directory "c:\program files\mingw\bin\../lib/gcc/mingw32/4.5.0/../../../../mingw32/include" ignoring nonexistent directory "c:/mingw/include" ignoring nonexistent directory "/mingw/include" ignoring duplicate directory "c:/program files/mingw/lib/gcc/../../lib/gcc/mingw32/4.5.0/include" ignoring duplicate directory "c:/program files/mingw/lib/gcc/../../lib/gcc/mingw32/4.5.0/include-fixed" ignoring nonexistent directory "c:/program files/mingw/lib/gcc/../../lib/gcc/mingw32/4.5.0/../../../../mingw32/include" ignoring nonexistent directory "/mingw/include" #include "..." search starts here: #include <...> search starts here: c:\program files\mingw\bin\../lib/gcc/mingw32/4.5.0/../../../../include c:\program files\mingw\bin\../lib/gcc/mingw32/4.5.0/include c:\program files\mingw\bin\../lib/gcc/mingw32/4.5.0/include-fixed End of search list. COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=c99' '-o' 'complexbug3.exe' '-mtune=i386' '-march=i386' c:/program files/mingw/bin/../libexec/gcc/mingw32/4.5.0/cc1.exe -fpreprocessed complexbug3.i -quiet -dumpbase complexbug3.c -mtune=i386 -march=i386 -auxbase complexbug3 -Wall -std=c99 -version -o complexbug3.s GNU C (GCC) version 4.5.0 (mingw32) compiled by GNU C version 4.5.0, GMP version 5.0.1, MPFR version 2.4.1, MPC version 0.8.1 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C (GCC) version 4.5.0 (mingw32) compiled by GNU C version 4.5.0, GMP version 5.0.1, MPFR version 2.4.1, MPC version 0.8.1 GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 6773400e8bc9df4b012089071ac4c86b COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=c99' '-o' 'complexbug3.exe' '-mtune=i386' '-march=i386' c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../../mingw32/bin/as.exe -o complexbug3.o complexbug3.s COMPILER_PATH=c:/program files/mingw/bin/../libexec/gcc/mingw32/4.5.0/;c:/program files/mingw/bin/../libexec/gcc/;c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../../mingw32/bin/ LIBRARY_PATH=c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/;c:/program files/mingw/bin/../lib/gcc/;c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../../mingw32/lib/;c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../ COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-std=c99' '-o' 'complexbug3.exe' '-mtune=i386' '-march=i386' c:/program files/mingw/bin/../libexec/gcc/mingw32/4.5.0/collect2.exe -Bdynamic -o complexbug3.exe c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../crt2.o c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/crtbegin.o -Lc:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0 -Lc:/program files/mingw/bin/../lib/gcc -Lc:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../../mingw32/lib -Lc:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/../../.. complexbug3.o -lmingw32 -lgcc_eh -lgcc -lmoldname -lmingwex -lmsvcrt -luser32 -lkernel32 -ladvapi32 -lshell32 -lmingw32 -lgcc_eh -lgcc -lmoldname -lmingwex -lmsvcrt c:/program files/mingw/bin/../lib/gcc/mingw32/4.5.0/crtend.o The result of executing complexbug3.exe is mathematically incorrect: (0.2 - I*0.3)*(0.3 - I*0.9) = (0.06, -0.09)
Confirmed on i?86-linux. Seems to be a problem with libgcc __mulxc3, linking with the libgcc from 4.4 makes it work for the failing releases.
Unincluded testcase: int main (void) { long double _Complex w = 0.2L - 0.3iL; w = w * (0.3L - (0.0F + 1.0iF) * 0.9L); __builtin_printf("(0.2 - I*0.3)*(0.3 - I*0.9) = (%g, %g)\n", (double) __real__ w, (double) __imag__ w); return 0; } On x86_64-linux the results look correct. Using w = w * (0.3L - 0.9iL); instead works too. And the results I get don't depend on libgcc version used (4.4 behaves like 4.6).
Mine.
It is caused by revision 147281: http://gcc.gnu.org/ml/gcc-cvs/2009-05/msg00255.html
Created attachment 23132 [details] gcc46-pr47473.patch Untested fix.
Author: jakub Date: Wed Jan 26 20:06:57 2011 New Revision: 169299 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=169299 Log: PR c/47473 * c-lex.c (interpret_float): If CPP_N_IMAGINARY, ensure EXCESS_PRECISION_EXPR is created with COMPLEX_TYPE instead of REAL_TYPE. * gcc.dg/torture/pr47473.c: New test. Added: trunk/gcc/testsuite/gcc.dg/torture/pr47473.c Modified: trunk/gcc/c-family/ChangeLog trunk/gcc/c-family/c-lex.c trunk/gcc/testsuite/ChangeLog
Fixed on the trunk so far.
Author: dnovillo Date: Wed Feb 2 17:53:51 2011 New Revision: 169624 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=169624 Log: PR c/47473 * c-lex.c (interpret_float): If CPP_N_IMAGINARY, ensure EXCESS_PRECISION_EXPR is created with COMPLEX_TYPE instead of REAL_TYPE. * gcc.dg/torture/pr47473.c: New test. Added: branches/google/integration/gcc/testsuite/gcc.dg/torture/pr47473.c Modified: branches/google/integration/gcc/c-family/ChangeLog branches/google/integration/gcc/c-family/c-lex.c branches/google/integration/gcc/testsuite/ChangeLog
Author: jakub Date: Thu Apr 7 18:24:43 2011 New Revision: 172113 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=172113 Log: Backported from mainline 2011-01-26 Jakub Jelinek <jakub@redhat.com> PR c/47473 * c-lex.c (interpret_float): If CPP_N_IMAGINARY, ensure EXCESS_PRECISION_EXPR is created with COMPLEX_TYPE instead of REAL_TYPE. * gcc.dg/torture/pr47473.c: New test. Added: branches/gcc-4_5-branch/gcc/testsuite/gcc.dg/torture/pr47473.c Modified: branches/gcc-4_5-branch/gcc/ChangeLog branches/gcc-4_5-branch/gcc/c-lex.c branches/gcc-4_5-branch/gcc/testsuite/ChangeLog
Fixed.