[OskarS]

I have no dog in this fight either way, I'm just very curious about the answer: if something like 30-40% in a Go executable that clocks in at more than a 100 megabytes is not taken up by either symbols, debug information or the pclntab, what exactly is in it? You mentioned "necessary metadata for garbage collection and reflection in a statically-compiled language" in a previous comment. Can you give some more details on what that means?

[rsc]

You can see the true size of the Go pclntab in ELF binaries using "readelf -S" and in Mac binaries using "otool -l". Its not zero.

One thing that did change from Go 1.15 to Go 1.16 is that we broke up the pclntab into a few different pieces. Again, it's all in the section headers. But the pieces are not in the actual binary's symbol table anymore, because they don't need to be. And since the format is different, we would have removed the old "runtime.pclntab" symbol entirely, except some old tools got mad if the symbol was missing. So we left the old symbol table entry present, with a zero length.

Clearly, we could emit many more symbols accurately describing all these specific pieces of the binary. But ironically that would just make the binary even larger. Leaving them out is probably the right call for nearly all use case.

Except perhaps trying to analyze binary size, although even there even symbols don't paint a full picture. OK, the pclntab is large. Why is it large? What are the specific things in it that are large? Symbols don't help there at all. You need to analyze the actual data, add debug prints to the linker, and so on.

That would make an interesting post, and perhaps we will write one like that. But not today.

[haberman]

> OK, the pclntab is large. Why is it large? What are the specific things in it that are large?

Is it reasonably easy to attribute individual entries in pclntab to specific symbols? If so I'd love to add this capability to https://github.com/google/bloaty which already tries to do per-symbol analysis of many other sections (eh_frame, rela.dyn, etc).

[rsc]

It's reasonably easy for a specific Go release, but the details can and often do change from release to release. At some point we may write a more detailed, general-purpose binary size analysis tool that could dump JSON for bloaty to import, but today that tool does not exist.