Bug 922 – export keyword causes undefined references on linux

Let's say you have a C lib that you want to link with your D app. You'd have a D 'header' like this: // need access to global_var defined in the C lib export extern extern (C) { int global_var; } The export keyword is there to facilitate dynamic linking on Windows. On linux, it causes link failure, both with static and dynamic linking. "undefined reference to `_imp__global_var'". This is not a actual error message, since I don't have access to a linux box. But similar errors have been reported by others. Supposedly, 'export' is not needed with ELF, as all symbols are visible by default. So I suppose dmd should ignore export on linux? The workaround we're using is to have a script remove 'export' from the files before compiling on linux. Pretty ugly. Littering code with version statements, or reorganizing it so we can put 'version (Windows) export:' somewhere wasn't very attractive either.

(In reply to description) > Let's say you have a C lib that you want to link with your D app. You'd have a D 'header' like this: > > // need access to global_var defined in the C lib > export extern extern (C) { > int global_var; > } > > The export keyword is there to facilitate dynamic linking on Windows. > On linux, it causes link failure, both with static and dynamic linking. > "undefined reference to `_imp__global_var'". This is not a actual error > message, since I don't have access to a linux box. But similar errors have > been reported by others. Let's avoid any potential "extern" isssues: # # export int global_var; # # void main(){ printf("%X\n", global_var); # a.d:(.gnu.linkonce.t_Dmain+0x4): undefined reference to `_imp__D1a10global_vari' > Supposedly, 'export' is not needed with ELF, as all symbols are visible by default. > So I suppose dmd should ignore export on linux? DMD doesn't use ELF's visibility features, thus export isn't required under Linux. > The workaround we're using is to have a script remove 'export' from the files > before compiling on linux. Pretty ugly. Littering code with version statements, > or reorganizing it so we can put 'version (Windows) export:' somewhere wasn't > very attractive either. Another option would be to use the GDC compiler. Added to DStress as http://dstress.kuehne.cn/run/e/export_01_A.d

Still happens, looks like the Windows mangling is applied to ELF.

Commits pushed to master at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/fdde441cfd341ad573b3dc9b11e994ed55adfe68 Fix issue 922 - Don't mangle exported symbol names on linux. https://github.com/dlang/dmd/commit/0152061d082bc6ea86fd27df734a3d1d81e825d9 Merge pull request #6250 from LemonBoy/manglelin Fix issue 922 - Don't mangle exported symbol names on linux.

Commits pushed to scope at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/fdde441cfd341ad573b3dc9b11e994ed55adfe68 Fix issue 922 - Don't mangle exported symbol names on linux. https://github.com/dlang/dmd/commit/0152061d082bc6ea86fd27df734a3d1d81e825d9 Merge pull request #6250 from LemonBoy/manglelin

Commits pushed to newCTFE at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/fdde441cfd341ad573b3dc9b11e994ed55adfe68 Fix issue 922 - Don't mangle exported symbol names on linux. https://github.com/dlang/dmd/commit/0152061d082bc6ea86fd27df734a3d1d81e825d9 Merge pull request #6250 from LemonBoy/manglelin