docs/probe_math_exception.c:

[uclinux-h8/uClibc.git] / docs / probe_math_exception.c

diff --git a/docs/probe_math_exception.c b/docs/probe_math_exception.c
index dbeccc5..dbc9020 100644 (file)
--- 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;
 }