Member Avatar for Annettest

I am trying to compile a program using make on Mac OS X with gcc4.2. But I'm getting this error:
fpu_control.h: No such file or directory

I have never had a problem with an include file before and I'm rather confused! I have googled fpu_control.h, but I can't find anywhere to download it.

If anyone can help, I would be very grateful!

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  • Latest Post Latest Post by SgtMe

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fpu_control.h is a glibc/Linux header that manipulates the x87 FPU control word (precision, rounding, exception masks). Apple OS X does not ship glibc, so the system toolchain on a Mac will not provide that header — which is why the compile stops with "No such file or directory" (as reported). 's suggestion to check include paths is valid, but simply copying a Linux header into the system includes is brittle unless the rest of the implementation is compatible.

There are three practical approaches that work for Mac builds:

  • Prefer the portable C99 <fenv.h> API when the code only needs to change rounding or save/restore the FP environment. Example pattern:
#include <fenv.h>

/* save current rounding mode */
int old = fegetround();

/* set rounding to nearest */
if (fesetround(FE_TONEAREST) != 0) { /* handle error */ }

/* floating-point work here */

/* restore rounding mode */
fesetround(old);

Use #pragma STDC FENV_ACCESS ON and, if relying on strict rounding semantics, compile with the appropriate flags (for GCC: -frounding-math) so the optimizer does not assume a fixed rounding mode.

  • If the program requires x87 precision control (extended vs double) or uses glibc-specific control-word tricks, consider a compatibility shim. The thread pointers from and to a small "fpmath"/fpu_control compatibility header are useful short-term fixes; verify the header’s license and test thoroughly on the target architectures.

  • If porting is impractical, build on a Linux environment (VM or container) where fpu_control.h is provided.

A useful first step is to search the source for fpu_control, fpu_control_t and _FPU_ macros to see whether the code only manipulates rounding (map to <fenv.h>) or needs low-level x87 precision (requires a shim or Linux build).

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Member Avatar for SgtMe

Make sure the header is in your include directory of the compiler/IDE. If you don't have the file, don't use it.

Edited by SgtMe because: n/a
Member Avatar for Annettest

Thanks SgtMe. Unfortunately, I need fpu_control.h. The program I am trying to compile that needs it was not written by me. It has to do with floating point precision.

I thought fpu_control.h would be a standard sort of file. But the only information I can find out about it is that it isn't included in my compiler (gcc 4.2). I just can't find out anything else about it! Thanks for your help.

Member Avatar for nezachem

This could be helpful.

Member Avatar for Annettest

Thank you very, very much nezachem and tawes01. These do indeed look very helpful! I googled for hours and couldn't find a thing!

Edited by Annettest because: n/a
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