Fix use of std::errc() for C++ < 11

[stbergmann]

After 8fc2538 "Reapply '[libc++] Optimize num_put integral functions' (#131613) (#133572)",

#include <locale>

started to fail with

$ clang++ -stdlib=libc++ -std=c++03 -fsyntax-only test.cc
In file included from test.cc:1:
~/llvm/inst/bin/../include/c++/v1/locale:1280:41: error: no matching constructor for initialization of 'std::errc'
1280 | _LIBCPP_ASSERT_INTERNAL(__res.__ec == std::errc(), "to_chars: invalid maximum buffer size computed?");
| ^
~/llvm/inst/bin/../include/c++/v1/__assert:94:86: note: expanded from macro '_LIBCPP_ASSERT_INTERNAL'
94 | # define _LIBCPP_ASSERT_INTERNAL(expression, message) _LIBCPP_ASSERT(expression, message)
| ^
~/llvm/inst/bin/../include/c++/v1/__assert:21:39: note: expanded from macro '_LIBCPP_ASSERT'
21 | (__builtin_expect(static_cast(expression), 1)
| ^
~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:262:36: note: candidate constructor not viable: requires single argument '__v', but no arguments were provided
262 | _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(errc)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
~/llvm/inst/bin/../include/c++/v1/__config:618:29: note: expanded from macro '_LIBCPP_DECLARE_STRONG_ENUM_EPILOG'
618 | _LIBCPP_HIDE_FROM_ABI x(__lx __v) : _v(__v) {}
| ^ ~~~~~~~~
~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:262:36: note: candidate constructor not viable: requires single argument '__v', but no arguments were provided
262 | _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(errc)
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
~/llvm/inst/bin/../include/c++/v1/__config:619:38: note: expanded from macro '_LIBCPP_DECLARE_STRONG_ENUM_EPILOG'
619 | _LIBCPP_HIDE_FROM_ABI explicit x(int __v) : _v(static_cast<__lx>(__v)) {}
| ^ ~~~~~~~
~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:143:29: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 0 were provided
143 | _LIBCPP_DECLARE_STRONG_ENUM(errc){
| ^~~~
1 error generated.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Stephan Bergmann (stbergmann)

Changes

After 8fc2538 "Reapply '[libc++] Optimize num_put integral functions' (#131613) (#133572)",

> $ cat test.cc
> #include <locale>

started to fail with

> $ clang++ -stdlib=libc++ -std=c++03 -fsyntax-only test.cc
> In file included from test.cc:1:
> ~/llvm/inst/bin/../include/c++/v1/locale:1280:41: error: no matching constructor for initialization of 'std::errc'
> 1280 | _LIBCPP_ASSERT_INTERNAL(__res.__ec == std::errc(), "to_chars: invalid maximum buffer size computed?");
> | ^
> ~/llvm/inst/bin/../include/c++/v1/__assert:94:86: note: expanded from macro '_LIBCPP_ASSERT_INTERNAL'
> 94 | # define _LIBCPP_ASSERT_INTERNAL(expression, message) _LIBCPP_ASSERT(expression, message)
> | ^
> ~/llvm/inst/bin/../include/c++/v1/__assert:21:39: note: expanded from macro '_LIBCPP_ASSERT'
> 21 | (__builtin_expect(static_cast<bool>(expression), 1)
> | ^
> ~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:262:36: note: candidate constructor not viable: requires single argument '__v', but no arguments were provided
> 262 | _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(errc)
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
> ~/llvm/inst/bin/../include/c++/v1/__config:618:29: note: expanded from macro '_LIBCPP_DECLARE_STRONG_ENUM_EPILOG'
> 618 | _LIBCPP_HIDE_FROM_ABI x(__lx __v) : _v(__v) {}
> | ^ ~~~~~~~~
> ~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:262:36: note: candidate constructor not viable: requires single argument '__v', but no arguments were provided
> 262 | _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(errc)
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
> ~/llvm/inst/bin/../include/c++/v1/__config:619:38: note: expanded from macro '_LIBCPP_DECLARE_STRONG_ENUM_EPILOG'
> 619 | _LIBCPP_HIDE_FROM_ABI explicit x(int __v) : _v(static_cast<__lx>(__v)) {}
> | ^ ~~~~~~~
> ~/llvm/inst/bin/../include/c++/v1/__system_error/errc.h:143:29: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 0 were provided
> 143 | _LIBCPP_DECLARE_STRONG_ENUM(errc){
> | ^~~~
> 1 error generated.

---

Full diff: https://github.com/llvm/llvm-project/pull/138522.diff

1 Files Affected:

• (modified) libcxx/include/locale (+1-1)

diff --git a/libcxx/include/locale b/libcxx/include/locale
index fa2620d883598..b206bf8f162f9 100644
--- a/libcxx/include/locale
+++ b/libcxx/include/locale
@@ -1277,7 +1277,7 @@ _LIBCPP_HIDE_FROM_ABI inline _OutputIterator num_put<_CharT, _OutputIterator>::_
   }
 
   auto __res = std::__to_chars_integral(__buffer_ptr, __char_buffer + __buffer_size, __uval, __base);
-  _LIBCPP_ASSERT_INTERNAL(__res.__ec == std::errc(), "to_chars: invalid maximum buffer size computed?");
+  _LIBCPP_ASSERT_INTERNAL(__res.__ec == std::errc(0), "to_chars: invalid maximum buffer size computed?");
 
   // Make letters uppercase
   if (__flags & ios_base::hex && __flags & ios_base::uppercase) {

[ldionne]

Looks like this fell through the cracks of our CI because this requires a combination of hardening mode = Debug and C++03. I don't think it makes sense to add that combination specifically, though -- while we should test all combinations in theory, in practice this is not feasible due to combinatorial explosion. So I think I'll take the patch as-is without increasing test coverage.