On Mon, May 2, 2011 at 12:02 PM, Lorenzo Bettini <lorenzo.bett...@gmail.com> wrote: > On 04/25/2011 06:36 PM, Bruno Haible wrote: >> >> Lorenzo Bettini wrote: >>> >>> on the manual I read >>> >>> "These Gnulib substitute header files rely on<config.h> being already >>> included. Furthermore<config.h> must be the first include in every >>> compilation unit. This means that to all your source files and likely >>> also to all your tests source files you need to add an ‘#include >>> <config.h>’ at the top. Which source files are affected? Exactly those >>> whose compilation includes a ‘-I’ option that refers to the Gnulib >>> library directory. " >> >> This paragraph is correct. >> >>> Would it be correct to put config.h only say in file1.cpp (and use the >>> ‘-I’ option that refers to the Gnulib library directory for that file >>> only), and not in file2.cpp and file3.cpp (where I don't use -I to refer >>> to gnulib library directory), and then link all the 3 files together by >>> also putting -lgnu? >> >> This will work find as long as data types defined in system headers >> defined by >> gnulib (such as structs, function pointers, pointers to socklen_t, etc.) >> are >> not exchanged between file1.cpp on one side and file2.cpp and file3.cpp on >> the >> other side. >> >> For example, if file1.cpp passes a 'struct stat' to file2.cpp through some >> function call or global variable, then you must be aware that the 'struct >> stat' >> that file1.cpp sees is 64-bit safe and therefore larger than the 32-bit >> 'struct stat' that file2.cpp sees. Similarly for 'struct sched_param' in >> <sched.h> and others. Typically this leads to crashes that are very hard >> to >> debug because the source code suggests to you that the two 'struct stat's >> are the same when they are not. > > Thanks for the answer > > but what about libraries? > For instance, I can live with including config.h in all .cpp library files, > but I wouldn't add it to library header files. Header files are not > referring to any struct defined in system header files of gnulib... at least > I guess (basically my library header files only use string form C++ standard > library)... would that be safe?
What why bruce is trying to create libposix... Bastien > thanks > Lorenzo > > -- > Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino > HOME: http://www.lorenzobettini.it MUSIC: http://www.purplesucker.com > BLOGS: http://tronprog.blogspot.com http://longlivemusic.blogspot.com > > > >
