Re: MSVC fails to compile floor.c with -fp:strict

[Michael Goffioul]

On Wed, Mar 14, 2012 at 9:48 AM, Bruno Haible <address@hidden> wrote:
> Michael Goffioul wrote:
>> I encountered a compilation error with MSVC when compiling floor.c in
>> strict floating-point mode (-fp:strict).
>
> Note that the use of -fp:strict also leads to test failures such as
>
>  test-hypot.h:41: assertion failed
>  FAIL: test-hypotl.exe
>
> MSVC appears to compile the test code (test-hypotl.c) in a different way,
> in such a way that a comparison of +Inf with +Inf fails.
>
> I'm therefore not sure this option can be recommended.

Initially I didn't use it, until I noticed a test failure in octave.
At some point, 2 complex numbers are compared with '<': in octave,
this is implemented by comparing the modules, then the arguments.
However, the result of b < a was true while a and b were the same.
This boiled down to rounding error accumulation in the FPU and the
only way to avoid it was to use -fp:strict. According to MSVC
documentation, this is the only way to get IEEE compliance
(http://msdn.microsoft.com/en-us/library/ms235601(v=vs.100).aspx) and
this is required in a software like octave.

Michael.