[PATCH] D142279: [cmake] Use LLVM_ENABLE_ASSERTIONS to enable assertions in libstdc++

[Steven Johnson via Phabricator via llvm-commits]

srj added a comment.

This change introduces compilation errors when building in at least some version(s) of gcc/g++; while what we're seeing is clearly a gcc/g++ bug, it would be good to avoid it if possible.

With gcc at version Debian 12.2.0-10:

  echo '#include <string>
  void f(int n) {
    for (int i = 0; i < n; i++) {
      std::string s;
      switch (i) {
      case 0: s = "x"; break;
      case 1: s = "y"; break;
      case 2: s = "z"; break;
      case 3: s = "w"; break;
      default: s = std::to_string(i); break;
      }
    }
  }
  ' | g++ -D_GLIBCXX_ASSERTIONS -x c++ - -O3 -Werror=restrict -c -o /dev/null

This will result in the compilation failure:

  In file included from /usr/include/c++/12/string:40,
                   from <stdin>:1:
  In static member function ‘static std::char_traits<char>::char_type* std::char_traits<char>::copy(char_type*, const char_type*, std::size_t)’,
      inlined from ‘static 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 ‘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 ‘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 ‘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 ‘void f(int)’ at <stdin>:6:17:
  /usr/include/c++/12/bits/char_traits.h:431:56: error: ‘void* __builtin_memcpy(void*, const void*, long unsigned int)’ accessing 9223372036854775810 or more bytes at offsets [18, 9223372036854775807] and 17 may overlap up to 9223372036854775813 bytes at offset -3 [-Werror=restrict]
    431 |         return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));
        |                                        ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

...again, while this seems almost certainly to be a bug in defining _GLIBCXX_ASSERTIONS for (some?) versions of gcc, it means you can't compile LLVM from source using this version of gcc with this patch in place.

If it possible to finesse this patch to detect the gcc version and avoid defining _GLIBCXX_ASSERTIONS? Alternately, could there be a way to continue allowing LLVM_ENABLE_ASSERTIONS to  be set, without defining _GLIBCXX_ASSERTIONS?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D142279/new/

https://reviews.llvm.org/D142279