[fpc-devel] Broken frac function in FPC3.1.1 / Windows x86_64

Bart bartjunk64 at gmail.com
Fri Apr 27 13:42:41 CEST 2018

On Wed, Apr 25, 2018 at 11:04 AM,  <info at wolfgang-ehrhardt.de> wrote:

> If you compile and run this 64-bit program on Win 64 you get a crash

And AFAICS your analysis of the cause (see bugtracker) is correct as well.

function fpc_frac_real(d: ValReal) : ValReal;compilerproc; assembler;
    cvttsd2si %xmm0,%rax
    { Windows defines %xmm4 and %xmm5 as first non-parameter volatile registers;
      on SYSV systems all are considered as such, so use %xmm4 }
    cvtsi2sd %rax,%xmm4
    subsd %xmm4,%xmm0

CVTTSD2SI — Convert with Truncation Scalar Double-Precision
Floating-Point Value to Signed Integer
This should not be used to get a ValReal result.


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