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From: Jason Merrill <jason@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-5906] libstdc++: check length in string append [PR103534] Date: Sat, 11 Dec 2021 04:58:24 +0000 (GMT) [thread overview] Message-ID: <20211211045824.402C93858D39@sourceware.org> (raw) https://gcc.gnu.org/g:2e8067041d1d69da02bd7578f58abc11eb35a04b commit r12-5906-g2e8067041d1d69da02bd7578f58abc11eb35a04b Author: Jason Merrill <jason@redhat.com> Date: Fri Dec 10 11:21:50 2021 -0500 libstdc++: check length in string append [PR103534] In the testcase for 103534 we get a warning about append leading to memcpy of a very large number of bytes overflowing the buffer. This turns out to be because we weren't calling _M_check_length for string append. Rather than do that directly, let's go through the public pointer append that calls it. PR c++/103534 libstdc++-v3/ChangeLog: * include/bits/basic_string.h (append (basic_string)): Call pointer append instead of _M_append directly. gcc/testsuite/ChangeLog: * g++.dg/warn/Wstringop-overflow-8.C: New test. Diff: --- libstdc++-v3/include/bits/basic_string.h | 8 ++++---- gcc/testsuite/g++.dg/warn/Wstringop-overflow-8.C | 10 ++++++++++ 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index 4007a8d2d7c..3da2f8088ac 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -1382,7 +1382,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 _GLIBCXX20_CONSTEXPR basic_string& append(const basic_string& __str) - { return _M_append(__str._M_data(), __str.size()); } + { return this->append(__str._M_data(), __str.size()); } /** * @brief Append a substring. @@ -1400,9 +1400,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 _GLIBCXX20_CONSTEXPR basic_string& append(const basic_string& __str, size_type __pos, size_type __n = npos) - { return _M_append(__str._M_data() - + __str._M_check(__pos, "basic_string::append"), - __str._M_limit(__pos, __n)); } + { return this->append(__str._M_data() + + __str._M_check(__pos, "basic_string::append"), + __str._M_limit(__pos, __n)); } /** * @brief Append a C substring. diff --git a/gcc/testsuite/g++.dg/warn/Wstringop-overflow-8.C b/gcc/testsuite/g++.dg/warn/Wstringop-overflow-8.C new file mode 100644 index 00000000000..d0ef5e73f93 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wstringop-overflow-8.C @@ -0,0 +1,10 @@ +// PR c++/103534 +// { dg-additional-options "-O -Wall" } + +#include <string> + +std::string foo(std::string x) +{ + // This used to get a bogus -Wstringop-overflow warning. + return std::string("1234567890123456") + x; +}
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