Fix iconv build with GCC mainline
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dj/TryBot-apply_patch |
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Patch applied to master at the time it was sent
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dj/TryBot-32bit |
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Build for i686
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Commit Message
Current GCC mainline produces -Wstringop-overflow errors building some
iconv converters, as discussed at
<https://gcc.gnu.org/pipermail/gcc/2021-July/236943.html>. Add an
__builtin_unreachable call as suggested so that GCC can see the case
that would involve a buffer overflow is unreachable; because the
unreachability depends on valid conversion state being passed into the
function from previous conversion steps, it's not something the
compiler can reasonably deduce on its own.
Tested with build-many-glibcs.py that, together with
<https://sourceware.org/pipermail/libc-alpha/2021-August/130244.html>,
it restores the glibc build for powerpc-linux-gnu.
Comments
Ping. This patch
<https://sourceware.org/pipermail/libc-alpha/2021-August/130315.html> is
pending review.
On Aug 19 2021, Joseph Myers wrote:
> Current GCC mainline produces -Wstringop-overflow errors building some
> iconv converters, as discussed at
> <https://gcc.gnu.org/pipermail/gcc/2021-July/236943.html>. Add an
> __builtin_unreachable call as suggested so that GCC can see the case
> that would involve a buffer overflow is unreachable; because the
> unreachability depends on valid conversion state being passed into the
> function from previous conversion steps, it's not something the
> compiler can reasonably deduce on its own.
Ok.
Andreas.
@@ -436,6 +436,12 @@ SINGLE(LOOPFCT) (struct __gconv_step *step,
return __GCONV_FULL_OUTPUT;
/* Now add characters from the normal input buffer. */
+ if (inlen >= MAX_NEEDED_INPUT)
+ /* 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. */
+ __builtin_unreachable ();
do
bytebuf[inlen++] = *inptr++;
while (inlen < MAX_NEEDED_INPUT && inptr < inend);