On 12/11/15 13:39 +0000, Jonathan Wakely wrote:
One downside of this change is that we introduce some (hopefully safe)
ODR violations, where inline functions and templates that depend on
_GLIBCXX_USE_C99_FOO might now be defined differently in C++98 and
C++11 code. Previously they had the same definition, even though in
C++11 mode the value of the _GLIBCXX_USE_C99_FOO macro might have been
sub-optimal (i.e. the C99 features were usable, but the macro said
they weren't). Those ODR violatiosn could be avoided if needed, by
always using the _GLIBCXX98_USE_C99_FOO macro in code that can be
included from either C++98 or C++11. We could still use the
_GLIBCXX11_USE_C99_FOO macro in pure C++11 code (such as the numeric
conversion functions) and get most of the benefit of this change.
This patch (relative to the previous one) would avoid the ODR
problems, by only using the C++98 macro in code that gets used in
C++98 and later, and using the _GLIBCXX11_XXX ones in code that is
never compiled as C++98 (specifically, the numeric conversion
functions).
Maybe this is a safer, more conservative change.