From: Stefan Liebler <stli@linux.ibm.com>
To: libc-alpha@sourceware.org
Cc: Stefan Liebler <stli@linux.ibm.com>
Subject: [PATCH] Avoid -Wstringop-overflow= warning in iconv module.
Date: Fri, 3 Jun 2022 14:52:51 +0200 [thread overview]
Message-ID: <20220603125251.3903158-1-stli@linux.ibm.com> (raw)
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.
---
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++;
--
2.36.1
next reply other threads:[~2022-06-03 12:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-03 12:52 Stefan Liebler [this message]
2022-06-13 6:31 ` Siddhesh Poyarekar
2022-06-14 9:10 ` Stefan Liebler
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