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debug/macho: no SymtabCmd data in *macho.Symtab Load after calling macho.Open() #38556

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ClarkGuan opened this issue Apr 21, 2020 · 4 comments
Open

debug/macho: no SymtabCmd data in *macho.Symtab Load after calling macho.Open() #38556

ClarkGuan opened this issue Apr 21, 2020 · 4 comments
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help wanted NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Unplanned

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@ClarkGuan
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ClarkGuan commented Apr 21, 2020 •
edited

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

$ go version
go version go1.14.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/didi/Library/Caches/go-build"
GOENV="/Users/didi/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/didi/dev/source/golang/gopath"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/n5/26_m50tn4_j2n3gmvt19300h0000gn/T/go-build965858086=/tmp/go-build -gno-record-gcc-switches -fno-common"

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
}
@andybons andybons changed the title no SymtabCmd data in *macho.Symtab Load after calling macho.Open() debug/macho: no SymtabCmd data in *macho.Symtab Load after calling macho.Open() Apr 21, 2020
@andybons andybons added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Apr 21, 2020
@andybons andybons added this to the Unplanned milestone Apr 21, 2020
@andybons
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Does this issue reproduce with the latest release?
No.

I’m confused. Are you saying this doesn‘t reproduce on tip? 1.14.2 is the latest release.

@andybons andybons added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Apr 21, 2020
@ClarkGuan
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Does this issue reproduce with the latest release?
No.

I’m confused. Are you saying this doesn‘t reproduce on tip? 1.14.2 is the latest release.

Sorry, wrong input... I mean I can reproduce with the latest release.

@andybons andybons removed the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Apr 22, 2020
@andybons
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Got it. Thanks.

@griesemer @rsc

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Change https://golang.org/cl/241237 mentions this issue: debug/macho: add SymtabCmd data to *macho.Symtab in parseSymtab

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