Alexander Arhipenko wrote:
I have 2 major comment on the updated patch. Consider following snippet from gcc.hpp: #if __GNUC__ >= 4 && !defined(__MINGW32__) && !defined(__CYGWIN__) # define BOOST_SYMBOL_EXPORT __attribute__((visibility("default"))) # define BOOST_SYMBOL_HIDE __attribute__((visibility("hidden"))) # define BOOST_SYMBOL_IMPORT BOOST_SYMBOL_EXPORT
...And assume following scenario: Someone is writing shared library (let's name it foo) with 'visilibility=hidden' option. Library foo is using e.g. boost_filesystem. In this case, all the symbols marked with BOOST_FILESYSTEM_DECL will be exported from foo library. This could easily break foo library's ABI (in case of migration to the newest boost version etc.), so BOOST_SYMBOL_IMPORT should be defined for gcc as empty macro: # define BOOST_SYMBOL_IMPORT.
The second comment: BOOST_EXCEPTION_EXPORT/IMPORT are intended for re-exporting exceptions from shared library. So, they should be defined for gcc as:
# define BOOST_EXCEPTION_EXPORT BOOST_SYMBOL_EXPORT # define BOOST_EXCEPTION_IMPORT BOOST_SYMBOL_EXPORT
and not as:
# define BOOST_EXCEPTION_EXPORT BOOST_SYMBOL_EXPORT # define BOOST_EXCEPTION_IMPORT BOOST_SYMBOL_IMPORT
Oh, now I am confused. How exactly those symbols are to be used? Say, I declare an exception class in a header -- what modifiers should I use? Do we need BOOST_WHATEVER_EXCEPTION_DECL? Maybe you can write up some guidance for library authors? - Volodya