This is the mail archive of the
libstdc++@gcc.gnu.org
mailing list for the libstdc++ project.
[patch] libstdc++/66327 don't pass null pointers to memcmp
- From: Jonathan Wakely <jwakely at redhat dot com>
- To: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Thu, 28 May 2015 23:35:47 +0100
- Subject: [patch] libstdc++/66327 don't pass null pointers to memcmp
- Authentication-results: sourceware.org; auth=none
std::equal((int*)0, (int*)0, p) and std::equal(p, p, (int*)0) are
valid for any input iterator p, and must not pass a null pointer to
memcpy.
Similarly, std::lexicographical_compare((int*)0, (int*)0, p, q) and
std::lexicographical_compare(p, q, (int*)0, (int*)0) are valid for any
input iterators p and q, and must not pass a null pointer to memcpy.
This is a rather brute force fix, but if noone has any better ideas
I'll commit this to the trunk and 4.9 and 5 branches tomorrow. (I
think it should go on the branches, because 4.9 is known to optimise
away null pointer checks after invalid calls to memcmp like this).
I am not adding tests for these as we have no way to use ubsan in the
testsuite at present. I plan to make that possible, and will go back
and add tests using -fsanitize=undefined for all the recent fixes I've
made for ubsan errors.
Tested powerpc64le-linux.
commit 323133a6f623e827c7e70fa6918c7149e8932443
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu May 28 20:23:22 2015 +0100
PR libstdc++/66327
* include/bits/stl_algobase.h (__equal<true>::equal): Do not call
memcmp with null pointers.
(__lexicographical_compare<true>::__lc): Do not call memcmp for empty
ranges.
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 409ef36..db065e2 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -812,6 +812,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static bool
equal(const _Tp* __first1, const _Tp* __last1, const _Tp* __first2)
{
+ if (__first1 == 0 || __first2 == 0)
+ return __first1 == __last1;
+
return !__builtin_memcmp(__first1, __first2, sizeof(_Tp)
* (__last1 - __first1));
}
@@ -917,9 +920,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
const size_t __len1 = __last1 - __first1;
const size_t __len2 = __last2 - __first2;
- const int __result = __builtin_memcmp(__first1, __first2,
- std::min(__len1, __len2));
- return __result != 0 ? __result < 0 : __len1 < __len2;
+ if (__len1 && __len2)
+ {
+ if (int __result = __builtin_memcmp(__first1, __first2,
+ std::min(__len1, __len2)))
+ {
+ return __result < 0;
+ }
+ }
+ return __len1 < __len2;
}
};