>>> We just discovered that every symbol is libjvm is being exported on OSX. >>> The OSX/BSD makefiles were copied from the linux ones and so have the >>> options for linker scripts and mapfiles, but as OSX doesn't support linker >>> scripts this is disabled by setting LDNOMAP=true - hence all symbols are >>> exported. >>> >>> However the OSX linker does support -exported_symbols_list >>> >>> https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/ld.1.html >>> >>> so I was wondering why the build wasn't modified to use that so that we >>> only export the JVM symbols we intend to export? (That's a question for the >>> macosx-port-dev folk :) ). >>> >>> Does anyone have experience using this such that we can get the hotspot >>> build fixed? >> >> Exports should be handled by the visibility settings. Until recently the >> JNIEXPORT macro resolved to nothing, now it sets __attribute__(("visibility" >> ("default))) (at least in 8, that should be backported to 7u if it hasn't >> already). The "default" visibility means export that symbol. To hide >> non-exported symbols you need to provide --fvisibility=hidden to gcc or >> clang when compiling. >> >> Hotspot has it's own jni_md.h headers with macros to determine JNIEXPORT, >> but they were wrong last I checked. It appears they attempted to clear the >> macro if a certain version of gcc was used, but what happens is it disables >> it for all versions of gcc above a particular release (which hasn't been >> used on Mac is quite some time). I pointed this out when the JNIEXPORT patch >> was posted for review to core-libs-dev (I think...), it was CC'd to the >> hotspot list too so someone has to have seen it. I'm not sure if it's been >> fixed or not. > > The visibility setting changes should aid with the primary exported > interfaces (JNI_ and JVM_) but looking at the build there are other symbols > (for Serviceability Agent I think) that get dynamically added to the mapfiles > - so I'm not sure if the visibility setting alone will help here. I think we > will still want the "exported_symbol_file" (but it seems whatever ld we are > using for OSX builds doesn't actually recognize that option ?? :( Or I'm > doing something wrong in trying to pass it)
Apple's ld supports "-exported_symbols_list filename" which is similar to (but not the same as) export map files for GNU ld. I don't know if the use of that argument overrides the -fvisibility setting though. Some minor experimentation should provide answers to that question... Can those symbols just be marked with JNIEXPORT or some similar macro? -DrD-
