public inbox for glibc-cvs@sourceware.org
help / color / mirror / Atom feed
* [glibc] Avoid -Wstringop-overflow= warning in iconv module.
@ 2022-06-14 9:08 Stefan Liebler
0 siblings, 0 replies; only message in thread
From: Stefan Liebler @ 2022-06-14 9:08 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=876cdf517d1c464ce3d8f7eaf4199565e5592f16
commit 876cdf517d1c464ce3d8f7eaf4199565e5592f16
Author: Stefan Liebler <stli@linux.ibm.com>
Date: Fri Jun 3 14:52:51 2022 +0200
Avoid -Wstringop-overflow= warning in iconv module.
On s390x when compiling with GCC 12, I get this warning:
utf8-utf16-z9.c:
../iconv/loop.c: In function ‘__from_utf8_loop_etf3eh_single’:
../iconv/loop.c:445:22: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
445 | bytebuf[inlen++] = *inptr++;
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~
../iconv/loop.c:381:17: note: at offset 4 into destination object ‘bytebuf’ of size 4
381 | unsigned char bytebuf[MAX_NEEDED_INPUT];
| ^~~~~~~
../iconv/loop.c:445:22: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
445 | bytebuf[inlen++] = *inptr++;
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~
../iconv/loop.c:381:17: note: at offset 5 into destination object ‘bytebuf’ of size 4
381 | unsigned char bytebuf[MAX_NEEDED_INPUT];
| ^~~~~~~
This patch tells the compiler that inend is always behind inptr which
avoids the warning. Note that the SINGLE function is only used to
implement the mb*towc*() or wc*tomb*() functions. Those functions use
inptr and inend pointing to a variable on stack, compute the inend pointer
or explicitly check the arguments which always leads to inptr < inend.
Special notes for backporters (according to Siddhesh Poyarekar):
If someone wants to backport this patch to release branches, they should
also backport the following wcrtomb change. Otherwise the assumptions
assumed by this patch are not true.
commit 9bcd12d223a8990254b65e2dada54faa5d2742f3
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Fri May 13 19:10:15 2022 +0530
wcrtomb: Make behavior POSIX compliant
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Diff:
---
iconv/loop.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/iconv/loop.c b/iconv/loop.c
index f8727a637a..09ade3b765 100644
--- a/iconv/loop.c
+++ b/iconv/loop.c
@@ -435,11 +435,17 @@ SINGLE(LOOPFCT) (struct __gconv_step *step,
return __GCONV_FULL_OUTPUT;
/* Now add characters from the normal input buffer. */
- if (inlen >= MAX_NEEDED_INPUT)
+ if (inlen >= MAX_NEEDED_INPUT || inptr >= inend)
/* Avoid a -Wstringop-overflow= warning when this loop is
unrolled. The compiler cannot otherwise see that this is
unreachable because it depends on (state->__count & 7) not
- being too large after a previous conversion step. */
+ being too large after a previous conversion step.
+ Starting with GCC 12, we also have mark the inptr >= inend
+ case as unreachable to omit the warning. Note that this SINGLE
+ function is only used to implement the mb*towc*() or wc*tomb*()
+ functions. Those functions use inptr and inend pointing to a
+ variable on stack, compute the inend pointer or explicitly check
+ the arguments which always leads to inptr < inend. */
__builtin_unreachable ();
do
bytebuf[inlen++] = *inptr++;
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2022-06-14 9:08 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-06-14 9:08 [glibc] Avoid -Wstringop-overflow= warning in iconv module Stefan Liebler
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).