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* [Bug c++/55787] New: Comparisons of double values don't work correctly @ 2012-12-22 15:24 tasin at hm dot edu 2012-12-22 17:30 ` [Bug c++/55787] " daniel.kruegler at googlemail dot com ` (4 more replies) 0 siblings, 5 replies; 6+ messages in thread From: tasin at hm dot edu @ 2012-12-22 15:24 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 Bug #: 55787 Summary: Comparisons of double values don't work correctly Classification: Unclassified Product: gcc Version: 4.7.2 Status: UNCONFIRMED Severity: critical Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: tasin@hm.edu Created attachment 29027 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29027 example code (as .ii) A simple comparison shows that floating point operations with the c++-type double doesn't set the floating status flag correctly. Changing the type of the members of the class Load to float or long double makes the application work correctly. In the attached example the free function bool operator<(const Load &, const Load &); doesn't work correctly. The example returns the output: Compare: true instead of Compare: false This example was compiled in different configurations and on different machines with the same wrong result: System configuration 1: --- Intel(R) Core(TM)2 CPU 6420 @ 2.13GHz 3 GB RAM (pae) Windows XP Professional Version 2002 SP3 32 bit arch --- Es werden eingebaute Spezifikationen verwendet. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=c:/mingw/bin/../libexec/gcc/mingw32/4.7.2/lto-wrapper.exe Ziel: mingw32 Konfiguriert mit: ../gcc-4.7.2/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 --disable-build-poststage1 -with-cxx --enable-version-specific-runtime-libs --build=mingw32 --prefix=/mingw Thread-Modell: win32 gcc-Version 4.7.2 (GCC) --- The build process call was: g++ -v -save-temps -Wall -pedantic -Wextra -o derror.exe src\derror.cpp --- derror.cpp --- // test routine to show the double error #include <iostream> #include <stdexcept> using namespace std; // class definition class Load { double m_dPowerOut, m_dEfficiency; public: Load(double powerOut, double eff=1) : m_dPowerOut(powerOut), m_dEfficiency(eff) { }; virtual double consumption() const; virtual ~Load() { } }; bool operator<(const Load &a, const Load &b); // class method definition double Load::consumption(void) const { if (m_dEfficiency==0.0) throw logic_error("Efficiency must not be 0"); return m_dPowerOut/m_dEfficiency; } /// free function // ... doesn't work correctly bool operator<(const Load &a, const Load &b) { return a.consumption() < b.consumption(); } /* // ... seems to work correctly, but the float-status-flag IMHO // still isn't correct bool operator<(const Load &a, const Load &b) { double bcon=b.consumption(); return a.consumption() < bcon; } */ int main() { try { Load pump(53.0, 0.43); bool cmp=(pump < pump); // should be false !!! cout << "Compare: " << (cmp ? "true" : "false") << endl; } catch (const exception &ex) { cerr << "Exception: " << ex.what() << endl; } return 0; } ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/55787] Comparisons of double values don't work correctly 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu @ 2012-12-22 17:30 ` daniel.kruegler at googlemail dot com 2012-12-22 18:29 ` schwab@linux-m68k.org ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: daniel.kruegler at googlemail dot com @ 2012-12-22 17:30 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 Daniel Krügler <daniel.kruegler at googlemail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |daniel.kruegler at | |googlemail dot com --- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-12-22 17:30:37 UTC --- Using gcc 4.8.0 20121209 (experimental) (also mingw, but 64-bit on Windows 7) returns "false" for me. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/55787] Comparisons of double values don't work correctly 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu 2012-12-22 17:30 ` [Bug c++/55787] " daniel.kruegler at googlemail dot com @ 2012-12-22 18:29 ` schwab@linux-m68k.org 2012-12-22 20:11 ` redi at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: schwab@linux-m68k.org @ 2012-12-22 18:29 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 --- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> 2012-12-22 18:28:49 UTC --- Most likely a dup of bug 323. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/55787] Comparisons of double values don't work correctly 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu 2012-12-22 17:30 ` [Bug c++/55787] " daniel.kruegler at googlemail dot com 2012-12-22 18:29 ` schwab@linux-m68k.org @ 2012-12-22 20:11 ` redi at gcc dot gnu.org 2012-12-31 16:12 ` rguenth at gcc dot gnu.org 2012-12-31 16:50 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: redi at gcc dot gnu.org @ 2012-12-22 20:11 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|critical |normal ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/55787] Comparisons of double values don't work correctly 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu ` (2 preceding siblings ...) 2012-12-22 20:11 ` redi at gcc dot gnu.org @ 2012-12-31 16:12 ` rguenth at gcc dot gnu.org 2012-12-31 16:50 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: rguenth at gcc dot gnu.org @ 2012-12-31 16:12 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |DUPLICATE --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> 2012-12-31 16:12:05 UTC --- Use -fexcess-precision=standard *** This bug has been marked as a duplicate of bug 323 *** ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/55787] Comparisons of double values don't work correctly 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu ` (3 preceding siblings ...) 2012-12-31 16:12 ` rguenth at gcc dot gnu.org @ 2012-12-31 16:50 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: redi at gcc dot gnu.org @ 2012-12-31 16:50 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55787 --- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-12-31 16:50:21 UTC --- If only ... cc1plus: sorry, unimplemented: -fexcess-precision=standard for C++ ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-12-31 16:50 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-12-22 15:24 [Bug c++/55787] New: Comparisons of double values don't work correctly tasin at hm dot edu 2012-12-22 17:30 ` [Bug c++/55787] " daniel.kruegler at googlemail dot com 2012-12-22 18:29 ` schwab@linux-m68k.org 2012-12-22 20:11 ` redi at gcc dot gnu.org 2012-12-31 16:12 ` rguenth at gcc dot gnu.org 2012-12-31 16:50 ` redi at gcc dot gnu.org
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