[FFmpeg-devel] [PATCH 2/2] configure: Use intel math.h header.

[Reimar Döffinger]

On 07.05.2014, at 15:52, Matt Oliver <protogonoi at gmail.com> wrote:
> icl when run under msvc12 currently generates incorrect code. This is due
> to an issue with msvc12's C99 additions to math.h. Several defines in
> msvc's math.h are not compatible with icl and will compile but generate
> erroneous results during runtime. An obvious example is that NAN from
> math.h evaluates to 0.0 under icl which is clearly not a correct value for
> NaN. This cause several errors that completly break FFmpeg.
> 
> There are several ways to fix this. 1) Force icl's floating point
> compliance but negatively impact performance in doing so. 2) Add compiler
> specific code into FFmpeg or 3) Have icl use its own native math header
> (which can also improve performance).

To be honest I find this quite ridiculous.
Almost two years should be enough for Intel to get the standard system headers to work correctly.
Or to put it differently: Using ICL starts to sound like a horribly bad idea if it already miscompiles basic system headers, which in turn IMHO raises some questions how many hacks we should accept for it.