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Fix pcprofiledump cross-endian condition (bug 22086) [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Tue, 5 Sep 2017 15:14:49 +0000
- Subject: Fix pcprofiledump cross-endian condition (bug 22086) [committed]
- Authentication-results: sourceware.org; auth=none
debug/pcprofiledump.c contains code that tries to handle other-endian
data. This uses a condition "(word & 0xfffffff0) == bswap_32
(0xdeb00000)". This condition is always false (the LHS always has the
low four bits zero, the RHS doesn't); a correct comparison would use
0x0fffffff. This results in -Werror=tautological-compare build
failures with the tile version of bits/byteswap.h and mainline GCC.
https://sourceware.org/ml/libc-testresults/2017-q3/msg00400.html
pcprofiledump.c: In function 'main':
pcprofiledump.c:118:39: error: bitwise comparison always evaluates to false
[-Werror=tautological-compare]
int must_swap = (word & 0xfffffff0) == bswap_32 (0xdeb00000);
^~
This patch fixes the condition. Tested for x86_64, and with
build-many-glibcs.py that it fixes the build for tilegx-linux-gnu.
(Note that I have not tested the actual pcprofiledump functionality,
native or cross endian, which lacks any testsuite coverage.) Committed.
2017-09-05 Joseph Myers <joseph@codesourcery.com>
[BZ #22086]
* debug/pcprofiledump.c (main): Use byte-swapped mask when
comparing word with byte-swapped constant.
diff --git a/debug/pcprofiledump.c b/debug/pcprofiledump.c
index a32cdef..6a9641e 100644
--- a/debug/pcprofiledump.c
+++ b/debug/pcprofiledump.c
@@ -115,7 +115,7 @@ main (int argc, char *argv[])
error (EXIT_FAILURE, errno, _("cannot read header"));
/* Check whether we have to swap the byte order. */
- int must_swap = (word & 0xfffffff0) == bswap_32 (0xdeb00000);
+ int must_swap = (word & 0x0fffffff) == bswap_32 (0xdeb00000);
if (must_swap)
word = bswap_32 (word);
--
Joseph S. Myers
joseph@codesourcery.com