On Wed, Apr 29, 2009 at 7:13 AM, Manuel López-Ibáñez <lopeziba...@gmail.com> wrote:
>>> * In C a const variable which is neither "extern" nor "static" is >>> visible outside of the current translation unit. In C++ it is not, >>> without an explicit "extern" declaration. I'm not sure how best to >>> handle this with -Wc++-compat, since C does not permit initializing an >>> "extern const" variable. >> >> C does permit it; there's a warning, not a pedwarn. Add an option to >> disable this warning (at least where "const" is used)? > > In any case, -Wc++-compat should warn about the difference in > behaviour, shouldn't it? > > I see the current code already handles this somehow: > > /* It is fine to have 'extern const' when compiling at C > and C++ intersection. */ > if (!(warn_cxx_compat && constp)) > warning (0, "%qs initialized and declared %<extern%>", name); > > BTW, why is this warned about? I believe I'm the author of that code. We had had this debate a couple of years back, when I had more resources to work on GCC. At the time, I was doing an incremental version of the amazing job Ian just accomplished and the CPP component had the construct that declared a variable as const but did not initialize it, and did not contain the `extern' specifier. That in C++ meant that the variable has an internal linkage -- but in C, the variable would have an external linkage. So, to write the code that meant the same thing in C and in C++, an 'extern' specifier is needed. The C people (I bellieve) at the time felt strongly that if not -Wc++-compat it probably should be warned about (because it is not "typical" C). -- Gaby
