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The feenableexcept() and fedisableexcept() APIs are now provided which let you detect when NaNs appear the moment it happens from anywhere in your program. Tests have also been added for the mission critical math functions expf() and erff(), whose perfect operation has been assured. See examples/trapping.c to see how to use this powerful functionality.
93 lines
3.9 KiB
C
93 lines
3.9 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2024 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/runtime/fenv.h"
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/**
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* Disables floating point exception trapping, e.g.
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*
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* feenableexcept(FE_INVALID | FE_DIVBYZERO |
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* FE_OVERFLOW | FE_UNDERFLOW);
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*
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* When trapping is enabled, something should handle SIGFPE. Calling
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* ShowCrashReports() at startup will install a generic handler with
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* backtraces and the symbol of the `si->si_code` which UNIX defines
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*
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* - `FPE_INTOVF`: integer overflow
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* - `FPE_INTDIV`: integer divide by zero
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* - `FPE_FLTDIV`: floating point divide by zero
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* - `FPE_FLTOVF`: floating point overflow
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* - `FPE_FLTUND`: floating point underflow
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* - `FPE_FLTRES`: floating point inexact
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* - `FPE_FLTINV`: invalid floating point operation
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* - `FPE_FLTSUB`: subscript out of range
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*
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* It's important to not use the `-ffast-math` or `-Ofast` flags when
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* compiling code that needs to be debugged. Using `-fsignaling-nans`
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* will also help, since GCC doesn't enable that by default.
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*
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* @param excepts may bitwise-or the following:
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* - `FE_INVALID`
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* - `FE_DIVBYZERO`
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* - `FE_OVERFLOW`
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* - `FE_UNDERFLOW`
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* - `FE_INEXACT`
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* - `FE_ALL_EXCEPT` (all of the above)
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* @see fetestexcept() if you don't want to deal with signals
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* @see feenableexcept() to turn it on in the first place
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*/
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int fedisableexcept(int excepts) {
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// limit to what we know
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excepts &= FE_ALL_EXCEPT;
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#ifdef __x86_64__
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#ifndef NOX87
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// configure 8087 fpu control word
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// setting the bits enables suppression
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unsigned short x87cw;
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asm("fstcw\t%0" : "=m"(x87cw));
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x87cw |= excepts;
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asm("fldcw\t%0" : /* no inputs */ : "m"(x87cw));
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#endif
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// configure modern sse control word
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// setting the bits enables suppression
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unsigned mxcsr;
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asm("stmxcsr\t%0" : "=m"(mxcsr));
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mxcsr |= excepts << 7;
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asm("ldmxcsr\t%0" : /* no inputs */ : "m"(mxcsr));
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return 0;
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#elif defined(__aarch64__)
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unsigned fpcr;
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unsigned fpcr2;
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fpcr = __builtin_aarch64_get_fpcr();
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fpcr2 = fpcr & ~(excepts << 8);
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if (fpcr != fpcr2)
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__builtin_aarch64_set_fpcr(fpcr2);
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return (fpcr >> 8) & FE_ALL_EXCEPT;
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#else
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return -1;
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#endif
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}
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