This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Fix sysdeps/ieee754/dbl-64/mpa.c for -Wuninitialized [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Thu, 21 May 2015 23:07:09 +0000
- Subject: Fix sysdeps/ieee754/dbl-64/mpa.c for -Wuninitialized [committed]
- Authentication-results: sourceware.org; auth=none
If you remove the "override CFLAGS += -Wno-uninitialized" in
math/Makefile, one of the errors you get is:
../sysdeps/ieee754/dbl-64/mpa.c: In function '__mp_dbl.part.0':
../sysdeps/ieee754/dbl-64/mpa.c:183:5: error: 'c' may be used uninitialized in this function [-Werror=maybe-uninitialized]
c *= X[0];
The problem is that the p < 5 case initializes c if p is 1, 2, 3 or 4
but not otherwise, and in fact p is positive for all calls to this
function so the uninitialized case can't actually occur. This patch
replaces the "if (p == 4)" last case with a comment so the compiler
can see that all paths do initialize c.
Tested for x86_64.
2015-05-21 Joseph Myers <joseph@codesourcery.com>
* sysdeps/ieee754/dbl-64/mpa.c (norm): Remove if condition on
(p == 4) case.
diff --git a/sysdeps/ieee754/dbl-64/mpa.c b/sysdeps/ieee754/dbl-64/mpa.c
index 7d6b0c5..7b52da9 100644
--- a/sysdeps/ieee754/dbl-64/mpa.c
+++ b/sysdeps/ieee754/dbl-64/mpa.c
@@ -119,7 +119,8 @@ __cpy (const mp_no *x, mp_no *y, int p)
#ifndef NO___MP_DBL
/* Convert a multiple precision number *X into a double precision
- number *Y, normalized case (|x| >= 2**(-1022))). */
+ number *Y, normalized case (|x| >= 2**(-1022))). X has precision
+ P, which is positive. */
static void
norm (const mp_no *x, double *y, int p)
{
@@ -135,7 +136,7 @@ norm (const mp_no *x, double *y, int p)
c = X[1] + R * X[2];
else if (p == 3)
c = X[1] + R * (X[2] + R * X[3]);
- else if (p == 4)
+ else /* p == 4. */
c = (X[1] + R * X[2]) + R * R * (X[3] + R * X[4]);
}
else
--
Joseph S. Myers
joseph@codesourcery.com