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GCC 12 warns about there could be overlap during memcpy #2134

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cngzhnp opened this issue May 9, 2023 · 3 comments · Fixed by #2137
Closed

GCC 12 warns about there could be overlap during memcpy #2134

cngzhnp opened this issue May 9, 2023 · 3 comments · Fixed by #2137
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@cngzhnp
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cngzhnp commented May 9, 2023

Describe your environment

GCC 12.2.0
OpenTelemetry Version 1.9.0

Steps to reproduce
Build opentelemetry-cpp project with "-Wall -Wextra" flags.

What is the expected behavior?
There should not be any warning due to these flags.

What is the actual behavior?
GCC shows a warning about overlap.

Additional context
Here is the output during compilation:

In static member function 'static constexpr std::char_traits<char>::char_type* std::char_traits<char>::copy(char_type*, const char_type*, std::size_t)',
    inlined from 'static constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:423:21,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Allocator>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_replace(size_type, size_type, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.tcc:532:22,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::assign(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:1647:19,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:815:28,
    inlined from 'opentelemetry::v1::ext::http::common::UrlParser::UrlParser(std::string)' at /3rdParty/opentelemetry-cpp/ext/include/opentelemetry/ext/http/common/url_parser.h:86:15:
/usr/include/c++/12/bits/char_traits.h:431:56: warning: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' accessing 9223372036854775810 or more bytes at offsets -4611686018427387902 and [-4611686018427387903, 4611686018427387904] may overlap up to 9223372036854775813 bytes at offset -3 [-Wrestrict]
  431 |         return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));
      |                                        ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
In static member function 'static constexpr std::char_traits<char>::char_type* std::char_traits<char>::copy(char_type*, const char_type*, std::size_t)',
    inlined from 'static constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:423:21,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Allocator>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_replace(size_type, size_type, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.tcc:532:22,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::assign(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:1647:19,
    inlined from 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]' at /usr/include/c++/12/bits/basic_string.h:815:28,
    inlined from 'opentelemetry::v1::ext::http::common::UrlParser::UrlParser(std::string)' at opentelemetry-cpp/ext/include/opentelemetry/ext/http/common/url_parser.h:125:13:
/usr/include/c++/12/bits/char_traits.h:431:56: warning: 'void* __builtin_memcpy(void*, const void*, long unsigned int)' accessing 9223372036854775810 or more bytes at offsets -4611686018427387902 and [-4611686018427387903, 4611686018427387904] may overlap up to 9223372036854775813 bytes at offset -3 [-Wrestrict]
  431 |         return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));
@cngzhnp cngzhnp added the bug Something isn't working label May 9, 2023
@lalitb
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lalitb commented May 10, 2023

Seems to be compiler bug to me - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105329

@cngzhnp
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cngzhnp commented May 10, 2023

If single character is wrapped by "std::string", all warnings are lost by the way. If does not bother, it would be fixed. What do you think?

@lalitb
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lalitb commented May 10, 2023

If single character is wrapped by "std::string", all warnings are lost by the way. If does not bother, it would be fixed. What do you think?

Agree

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