[git commit] stdio: Fix printing 0.0
Bernhard Reutner-Fischer
rep.dot.nop at gmail.com
Mon Dec 15 16:27:49 UTC 2014
commit: http://git.uclibc.org/uClibc/commit/?id=f8e05f3850e51673522216f23533bf7146359dcd
branch: http://git.uclibc.org/uClibc/commit/?id=refs/heads/master
We were relying on FE_DIVBYZERO being turned off when printing
"%f", +-.0
Avoid the whole issue by looking at the sign-bit (in a rough
approximation).
Note that we do not handle gracefully:
printf ("\n%llf\n", -0.0);
printf ("\n%llf\n", 0.0);
nor %Lf for both when NOT cast to long double. Avoiding an FPE due to
broken numbers like these does not make sense to me.
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop at gmail.com>
---
libc/stdio/_fpmaxtostr.c | 13 +++++++------
1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/libc/stdio/_fpmaxtostr.c b/libc/stdio/_fpmaxtostr.c
index f7ea792..3580584 100644
--- a/libc/stdio/_fpmaxtostr.c
+++ b/libc/stdio/_fpmaxtostr.c
@@ -45,11 +45,6 @@
*/
#define isnan(x) ((x) != (x))
-/* Without seminumerical functions to examine the sign bit, this is
- * about the best we can do to test for '-0'.
- */
-#define zeroisnegative(x) ((1./(x)) < 0)
-
/*****************************************************************************/
/* Don't change anything that follows peroid!!! ;-) */
/*****************************************************************************/
@@ -262,7 +257,13 @@ ssize_t _fpmaxtostr(FILE * fp, __fpmax_t x, struct printf_info *info,
if (x == 0) { /* Handle 0 now to avoid false positive. */
#ifdef __UCLIBC_HAVE_SIGNED_ZERO__
- if (zeroisnegative(x)) { /* Handle 'signed' zero. */
+ union {
+ double x;
+ struct {
+ unsigned int l1, l2;
+ } i;
+ } u = {x};
+ if (u.i.l1 ^ u.i.l2) { /* Handle 'signed' zero. */
*sign_str = '-';
}
#endif /* __UCLIBC_HAVE_SIGNED_ZERO__ */
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