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<  Erlang patches mailing list  ~  unix/sys_float.c mishandles errno
mdempsky
Posted: Wed Jan 09, 2008 12:49 am Reply with quote
User Joined: 24 Sep 2007 Posts: 118
The code in unix/sys_float.c assumes that if strtod(3) sets errno to
ERANGE then there was a problem parsing the value. However, according
to POSIX, the actual indication of an error is that it also returned
0.0, HUGE_VAL, or -HUGE_VAL. This causes a problem on OS X 10.5 when
trying to read denormalized floating-point numbers because OS X's
strtod(3) implementation sets errno to ERANGE for denormals.

The patch below changes the errno check to be consistent with POSIX.

--- sys_float.c.orig 2008-01-02 10:38:16.000000000 -0800
+++ sys_float.c 2008-01-02 10:39:55.000000000 -0800
@@ -705,9 +705,7 @@
if (*s) /* That should be it */
return -1;

-#ifdef NO_FPE_SIGNALS
errno = 0;
-#endif
__ERTS_FP_CHECK_INIT(fpexnp);
*fp = strtod(buf, &t);
__ERTS_FP_ERROR_THOROUGH(fpexnp, *fp, return -1);
@@ -720,14 +718,14 @@
__ERTS_FP_ERROR_THOROUGH(fpexnp, *fp, return -1);
}

+ if ((*fp == 0.0 || *fp == HUGE_VAL || *fp == -HUGE_VAL) && errno
== ERANGE) {
#ifdef DEBUG
- if (errno == ERANGE)
fprintf(stderr, "errno = ERANGE in list_to_float\n\r");
#endif
#ifdef NO_FPE_SIGNALS
- if (errno == ERANGE)
return -1;
#endif
+ }
/*
** Replaces following code:
** if (errno == ERANGE) {
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