Bug #7142

mingw TestFloat#test_round_with_precision failure

Added by h.shirosaki (Hiroshi Shirosaki) about 8 years ago. Updated about 8 years ago.

Target version:
ruby -v:
ruby 2.0.0dev (2012-10-09 trunk 37127) [i386-mingw32]


Trunk ruby on Windows XP x86 with mingw-w64 gcc 4.7.2 has the following test failure.

1) Failure:
test_round_with_precision(TestFloat) [C:/Users/Worker/Jenkins/workspace/ruby-trunk-x86-build/test/ruby/test_float.rb:389]:
expected but was

I get the failure with make test-all TESTS="-qv -n test_round_with_precision".

But it's strange that I don't get the failure with make test-all TESTS="-qv ruby/test_float.rb".
And This failure doesn't occur on Win7.

Floating-point precision seems to be changed for some reason. Mingw-w64 has own pow() implementation and the precision of pow(10, ndigits) is not proper.
I found calling (({_controlfp(_PC_64, _MCW_PC)})) before pow() improves precision and fixes this failure.

I'll commit this patch if there is no other better fix.

Index: include/ruby/win32.h
--- include/ruby/win32.h (revision 37136)
+++ include/ruby/win32.h (working copy)
@@ -764,7 +764,7 @@
} /* extern "C" { */

-#ifdef MINGW64
+#if defined(MINGW64)

  • Use powl() instead of broken pow() of x86_64-w64-mingw32.
  • This workaround will fix test failures in test_bignum.rb, @@ -775,6 +775,24 @@ { return powl(x, y); } +#elif defined(__MINGW64_VERSION_MAJOR) +/*
    • * Set floating point precision for pow() of mingw-w64 x86.
    • * With default precision the result is not proper on WinXP.
    • */ +static inline double +rb_w32_pow(double x, double y) +{
    • double r;
    • unsigned int default_control = _controlfp(0, 0);
    • _controlfp(_PC_64, _MCW_PC);
    • r = pow(x, y);
    • /* Restore setting */
    • _controlfp(default_control, _MCW_PC);
    • return r; +} +#endif +#if defined(MINGW64_VERSION_MAJOR) || defined(MINGW64__) #define pow rb_w32_pow #endif



Updated by Anonymous about 8 years ago

  • Status changed from Open to Closed
  • % Done changed from 0 to 100

This issue was solved with changeset r37168.
Hiroshi, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

win32.h: set floating point precision for pow()

  • include/ruby/win32.h (rb_w32_pow): set floating point precision for mingw-w64 x86 pow(). This improves the precision of pow() on Windows XP for TestFloat#test_round_with_precision failure. [ruby-core:47911] [Bug #7142]

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