[PATCH] Fix version namespace build

[Jonathan Wakely]

On 09/02/21 22:05 +0100, François Dumont via Libstdc++ wrote:
>    libstdc++: Fix versioned namespace build
>
>    libstdc++-v3/ChangeLog:
>
>            * libsupc++/eh_ptr.cc (exception_ptr(__safe_bool)): Define if
>            _GLIBCXX_EH_PTR_COMPAT is defined.
>            (exception_ptr::_M_safe_bool_dummy()): Likewise.
>            (exception_ptr::operator!()): Likewise.
>            (exception_ptr::opeerator __safe_bool()): Likewise.
>
>Ok to commit ?

No, this is not correct. Those functions are declared in the
header if included from C++98 code:

#if (__cplusplus < 201103L) || defined (_GLIBCXX_EH_PTR_COMPAT)
       typedef void (exception_ptr::*__safe_bool)();

       // For construction from nullptr or 0.
       exception_ptr(__safe_bool) _GLIBCXX_USE_NOEXCEPT;
#endif

With your change, C++98 code that calls those functions will be unable
to link to libstdc++.so.8 because the functions won't be defined in
the library.

The simplest fix would be to revert this change:

--- a/libstdc++-v3/libsupc++/eh_ptr.cc
+++ b/libstdc++-v3/libsupc++/eh_ptr.cc
@@ -25,7 +25,12 @@
  #include <bits/c++config.h>
  #include "eh_atomics.h"

+#if ! _GLIBCXX_INLINE_VERSION
+// This macro causes exception_ptr to declare an older API (with corresponding
+// definitions in this file) and to mark some inline functions as "used" so
+// that definitions will be emitted in this translation unit.
  #define _GLIBCXX_EH_PTR_COMPAT
+#endif

  #include <exception>
  #include <bits/exception_ptr.h>

But that leaves the unwanted operator== definitions in libstdc++.so.8
so the attached patch (only tested with unversioned namespace) is
probably what we want to do. Does it fix the problem?


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