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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.
This commit is contained in:
Jason Merrill 2021-12-10 11:21:50 -05:00
parent 0bceef1671
commit 2e8067041d
2 changed files with 14 additions and 4 deletions
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10
gcc/testsuite/g++.dg/warn/Wstringop-overflow-8.C Normal file
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@ -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;
}

8
libstdc++-v3/include/bits/basic_string.h
View File

@ -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.