Jasper Woudenberg (Feb 04 2025 at 18:55): Jasper Woudenberg (Feb 04 2025 at 18:55):The static site generation platform I'm working on has a file watcher which rebuilds the site if a source file changes. I'd also like to rebuild if the main.roc file which contains the build rules changes. To do that currently I'm letting the host exec into a fresh roc run .. call on main.roc, but this means that if there's compiler errors the file watching process will exit.
I'm trying to change this logic to instead run roc build --lib main.roc in a spawned process, then dlopen the shared library roc outputs. I'm running into a problem though: dlopen fails saying roc_alloc could not be found. That sort of makes sense, roc_alloc is defined in the binary that's currently running and which is calling dlopen.
From searching I've learned that the -rdynamic linker flag exists for this precise purpose, and I've enabled it in my build.zig file for the linker=legacy library I'm building. (I haven't had luck using the surgical linker for this platform since a while ago, so it's out of the picture). Even with -rdynamic set the linker error is still there.
I'm still learning about linking so was hoping someone might be able to confirm/reject this hypothesis: Could it be that this is because the linking that Roc performs as part of building the final binary overrules me setting rdynamic on the library I build? If so, is there currently a way to tell the legacy linker it should be using the rdynamic option?
If it doesn't work out I can go back to using the exec option for now, I'm just curious and looking to learn :smile:
Brendan Hansknecht (Feb 04 2025 at 22:02):If you are using --lib it shouldn't be using the legacy linker at all
Brendan Hansknecht (Feb 04 2025 at 22:03):As for -rdynamic my guess is that zig is helpfully garbage collecting your unused code
Brendan Hansknecht (Feb 04 2025 at 22:03):As such, roc_alloc and friends are not available
Brendan Hansknecht (Feb 04 2025 at 22:04):Frankly, rdynamic is kinda a hack anyway and I'm glad we plan to make more things explicit to avoid these pains
Jasper Woudenberg (Feb 04 2025 at 22:11):Ah yeah, it makes sense that --lib wouldn't be using the linker.
Shouldn't zig leave roc_alloc alone, since it's explicitly marked as an extern fn and zig can't know what the artifact it produces might get linked with later?
Jasper Woudenberg (Feb 04 2025 at 22:13):Frankly, rdynamic is kinda a hack anyway and I'm glad we plan to make more things explicit to avoid these pains
Yeah, reading the new plans it sounds like things will be decidedly less magical in the future. Exciting times!
Brendan Hansknecht (Feb 04 2025 at 22:19):When making executables extern is often a lie
Brendan Hansknecht (Feb 04 2025 at 22:19):Cause the executable is seen as the final thing
Last updated: Jul 26 2025 at 12:14 UTC