"Boris" <[EMAIL PROTECTED]> writes: > Paul Pluzhnikov wrote: >> Assuming Linux, the answer is to use linker version script and >> explicitly make only your "public" interface visible, hiding >> everything else. > > Why is this so complicated? If I build a shared library like this: > > g++ -shared -o libfoo.so foo.o -lbar > > why doesn't the linker (I'm on Linux) hides automatically all the symbols > from libbar?
Because it can't know that's what you wanted it to do. Linking against archive library is almost the same as linking against an object. Should it also hide all objects from foo.o as well, and export nothing at all? > Isn't it safe to assume that libfoo probably wants to get > linked to some symbols in libbar but does not want to export these symbols? Not at all. A lot of people build their DSOs like this: - compile a bunch of sources in multiple directories into src1.a, src2.a, etc. - link them all into giant DSO like this: ld -shared -o giant.so --whole-archive src1.a src2.a --no-whole-archive In this case, the user explicitly wants to have everything in src*.a to be included and exported from giant.so > In my example where I link a shared library to the Expat XML parser I want > to make use of some functions from Expat and not create a shared library > which among others provides the same functions as Expat does already. So why are you linking agains libExpat.a ? Link against libExpat.so instead. You probably want to use code from Expat, do not want to force the user to link agains libExpat.so, and do not want that code to conflict with potentially different version of Expat that the user might link against, and you want the static linker to guess your intent. Tough luck. You'll have to explicitly tell the linker what your intent is. > What's > the rationale of exporting all symbols by default? The rationale is that shared libraries should work just as archive libraries did. When you do 'ar r foo.a foo.o bar.o' foo.a has everything that foo.o and bar.o had. So 'ld -shared -o foo.so foo.o bar.o' should do the same. And as I said, from linker perspective there is not buch difference between 'ld -shared -o foo.so foo.o bar.o' and 'ld -shared -o foo.so foo.o bar.a' Cheers, -- In order to understand recursion you must first understand recursion. Remove /-nsp/ for email. _______________________________________________ help-gplusplus mailing list help-gplusplus@gnu.org http://lists.gnu.org/mailman/listinfo/help-gplusplus
