diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/probe_math_exception.c | 33 |
1 files changed, 28 insertions, 5 deletions
diff --git a/docs/probe_math_exception.c b/docs/probe_math_exception.c index dbeccc5cc..dbc9020d4 100644 --- a/docs/probe_math_exception.c +++ b/docs/probe_math_exception.c @@ -5,20 +5,40 @@ #define _ISOC99_SOURCE 1 #define _GNU_SOURCE 1 +#include <stdint.h> #include <math.h> #include <fenv.h> #include <stdio.h> int main(int argc, char **argv) { - float infF = HUGE_VALF * 2; + float largest, small, t, inf_float; + + largest = small = 1; + while (1) { + t = largest + small; + /* optimizations may make plain "t == largest" unreliable */ + if (memcmp(&t, &largest, sizeof(float)) == 0) + break; + if (isfinite(t)) { + largest = t; + small *= 2; + continue; + } + small /= 2; + } + inf_float = largest + largest; + //printf("%.40g ", largest); + //printf("[%llx]\n", (long long) (*(uint32_t *)&largest)); feclearexcept(FE_ALL_EXCEPT); -// printf("%.40e\n", 1.0 / 0.0); // FE_DIVBYZERO -// printf("%.40e\n", nextafterf(HUGE_VALF, infF)); // no exceptions in glibc 2.4 + //t = 1.0 / 0.0; // simple test: FE_DIVBYZERO + //t = nextafterf(largest, 1); // glibc 2.8: no math exceptions raised + //t = nextafterf(largest, largest); // glibc 2.8: no math exceptions raised + //t = nextafterf(largest, inf_float); // glibc 2.8: FE_INEXACT FE_OVERFLOW -#define PREX(ex) do { if (fetestexcept(ex)) printf(#ex); } while(0) +#define PREX(ex) do { if (fetestexcept(ex)) printf(#ex " "); } while(0) #ifdef FE_INEXACT PREX(FE_INEXACT); #endif @@ -36,6 +56,9 @@ int main(int argc, char **argv) #endif if (fetestexcept(FE_ALL_EXCEPT)) printf("\n"); - printf("done\n"); + else + printf("no math exceptions raised\n"); + + printf("%.40g\n", t); return 0; } |