FETESTEXCEPT(3P)

✨ FETESTEXCEPT ✨

okay bestie, this one lives in the POSIX Programmer's Manual — volume 3P, the FETESTEXCEPT(3P) page 💖 it's all about testing floating-point exception flags, which sounds scary but is literally just "hey, which of these little flags are currently set?" 🚩

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🌸 PROLOG 🌸

so like, quick heads up before we dive in 👑 — this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so bestie, go check the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface might not even be implemented on Linux at all. no cap. 😭

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💅 NAME 💅

fetestexcept — test floating-point exception flags 🚩✨

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🎀 SYNOPSIS 🎀

#include <fenv.h>

int fetestexcept(int excepts);

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🦋 DESCRIPTION 🦋

okay so first thing, the functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional — and this volume of POSIX.1‐2017 defers to the ISO C standard. periodt. 📜

Now the actual tea ☕: the fetestexcept() function shall determine which of a specified subset of the floating-point exception flags are currently set. The excepts argument specifies the floating-point status flags to be queried. it's giving "tell me which of these are on right now" 💅

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🔥 RETURN VALUE 🔥

fetestexcept() shall return the value of the bitwise-inclusive OR of the floating-point exception macros corresponding to the currently set floating-point exceptions included in excepts. so basically it ORs together all the ones that are actually lit up 🔥👑

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🌈 ERRORS 🌈

No errors are defined. iconic, honestly. nothing to worry about 💜

The following sections are informative. (iykyk — that means they're the vibes-and-context sections, not the strict requirements 🧚)

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💖 EXAMPLES 💖

the following example calls function f() if an invalid exception is set, and then function g() if an overflow exception is set:

#include <fenv.h>
/* ... */
{
    #pragma STDC FENV_ACCESS ON
    int set_excepts;
    feclearexcept(FE_INVALID | FE_OVERFLOW);
    // maybe raise exceptions
    set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
    if (set_excepts & FE_INVALID) f();
    if (set_excepts & FE_OVERFLOW) g();
    /* ... */
}

see how it clears first, then checks? ate. 💅

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🌸 APPLICATION USAGE 🌸

None. slay, nothing to add 🫶

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🎀 RATIONALE 🎀

None. we love a low-maintenance section ✨

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🦋 FUTURE DIRECTIONS 🦋

None. the future is bright and also empty here 💜

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⭐ SEE ALSO ⭐

• feclearexcept()
• fegetexceptflag()
• feraiseexcept()

The Base Definitions volume of POSIX.1‐2017, <fenv.h> 📚

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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ngl the copyright section is the longest part of this whole page and that's so real 😭

and that's the whole thing bestie, mwah 💋 — brought to you by IEEE/The Open Group, 2017 🎀💖✨