golang/go

debug/macho: no SymtabCmd data in *macho.Symtab Load after calling macho.Open()

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#38,556 opened on Apr 21, 2020

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Description

What version of Go are you using (go version)?

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

What did you do?

file, _ := macho.Open("xxx.o")    // which has Mach-O format with MH_OBJECT type
for i, l := range file.Loads {
    switch lo := l.(type) {
        case *macho.Symtab:
            fmt.Println(lo.SymtabCmd)    // nothing but zero value
    }
}

What did you expect to see?

Non-zero value of lo.SymtabCmd.

What did you see instead?

Zero value of lo.SymtabCmd.

Possible causes

parseSymtab() function in debug/macho/file.go:

        ...
	st := new(Symtab)
	st.LoadBytes = LoadBytes(cmddat)
	st.Syms = symtab
	return st, nil
}

ignore st.SymtabCmd ? It cound be:

        ...
	st := new(Symtab)
	st.LoadBytes = LoadBytes(cmddat)
	st.Syms = symtab
        st.SymtabCmd = *hdr
	return st, nil
}

Contributor guide

Research direction
Examine the parseSymtab function in debug/macho/file.go and add the missing assignment of st.SymtabCmd = *hdr to preserve the SymtabCmd data.
Tech stack
go
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Go
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75