cc @randall77 for decision

This was useful for something I've been working on

Could you describe how it would be useful?

Darwin objdump (Apple LLVM version 9.0.0 (clang-900.0.38)) does not have this option. My linux objdump does, but it didn't make the cut for the binary's one-page help page.

I wanted to extract the text for a given symbol, or set of symbols.

Yes this is probably a niche use case, and there are other ways to do it (hence why its not made it into LLVM-based objdump). On the other hand its a fairly simple feature.

FWIW this gist shows a script to do it using the cmd/internal/objfile package https://gist.github.com/mmcloughlin/6167deb9591994183e96210d612c88a0 (objfile and other packages copied out of the internal namespace).

It seems to me that you really want to be using a programmatic interface (like the gist) and not parsing objdump output. It seems a lot simpler than shelling out to objdump, parsing the output, then opening the file and reading the ranges you want.

objdump output is for humans. I don't want to add to it unless it's useful for humans. There are other interfaces that programs can use to access this information.

There are other interfaces that programs can use to access this information.

I think the only problem with this is that the package you need to access objdump-like functionality is in an internal package.

Actually occurs to me that this feature may have been more useful in nm, for my use case at least. Then the script to do this is a simple combination of go tool nm and dd.

This works on public interfaces only (but ELF only):

package main

import (
	"debug/elf"
	"fmt"
	"os"
)

func main() {
	file := os.Args[1]
	e, err := elf.Open(file)
	if err != nil {
		panic(err)
	}
	syms, err := e.Symbols()
	if err != nil {
		panic(err)
	}
	for _, s := range syms {
		if elf.ST_TYPE(s.Info) != elf.STT_FUNC {
			continue
		}
		sect := e.Sections[s.Section]
		fmt.Printf("%16x %16x %s\n", s.Value-sect.Addr+sect.Offset, s.Size, s.Name)
	}
}

It should be easy to grab the actual instruction bytes using the elf.Section.ReaderAt.

Nice. Of course the benefit of the internal package is the abstraction layer over the object file format.

Feel free to close the ticket, it's not something I feel strongly about.