cmd/cgo: use the export'ed file/line in error messages #76118

ariel-anieli · 2025-10-30T12:53:38Z

When an unpinned Go pointer (or a pointer to an unpinned Go pointer) is
returned from Go to C,

 1  package main
 2
 3  import (
 4          "C"
 5  )
 6
 7  //export foo
 8  func foo(CLine *C.char) string {
 9          return C.GoString(CLine)
10  }
11
12
13  func main() {
14  }

The error message mentions the file/line of the cgo wrapper,

panic: runtime error: cgo result is unpinned Go pointer or points to unpinned Go pointer

goroutine 17 [running, locked to thread]:
panic({0x798f2341a4c0?, 0xc000112000?})
        /usr/lib/go/src/runtime/panic.go:802 +0x168
runtime.cgoCheckArg(0x798f23417e20, 0xc000066e50, 0x0?, 0x0, {0x798f233f5a62, 0x42})
        /usr/lib/go/src/runtime/cgocall.go:679 +0x35b
runtime.cgoCheckResult({0x798f23417e20, 0xc000066e50})
        /usr/lib/go/src/runtime/cgocall.go:795 +0x4b
_cgoexp_3c910ddb72c4_foo(0x7ffc9fa9bfa0)
        _cgo_gotypes.go:65 +0x5d
runtime.cgocallbackg1(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0)
        /usr/lib/go/src/runtime/cgocall.go:446 +0x289
runtime.cgocallbackg(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0)
        /usr/lib/go/src/runtime/cgocall.go:350 +0x132
runtime.cgocallbackg(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0)
        <autogenerated>:1 +0x2b
runtime.cgocallback(0x0, 0x0, 0x0)
        /usr/lib/go/src/runtime/asm_amd64.s:1082 +0xcd
runtime.goexit({})
        /usr/lib/go/src/runtime/asm_amd64.s:1693 +0x1

The cgo wrapper (_cgoexp_3c910ddb72c4_foo) is located in a temporary
build artifact (_cgo_gotypes.go)

$ go tool cgo -objdir objdir parse.go
$ cat -n objdir/_cgo_gotypes.go | sed -n '55,70p'
    55  //go:cgo_export_dynamic foo
    56  //go:linkname _cgoexp_d48770e267d1_foo _cgoexp_d48770e267d1_foo
    57  //go:cgo_export_static _cgoexp_d48770e267d1_foo
    58  func _cgoexp_d48770e267d1_foo(a *struct {
    59                  p0 *_Ctype_char
    60                  r0 string
    61          }) {
    62          a.r0 = foo(a.p0)
    63          _cgoCheckResult(a.r0)
    64  }

The file/line of the export'ed function is expected in the error message.

Use it in error messages.

panic: runtime error: cgo result is unpinned Go pointer or points to unpinned Go pointer

goroutine 17 [running, locked to thread]:
panic({0x7df72b1d8ae0?, 0x3ec8a1790030?})
        /mnt/go/src/runtime/panic.go:877 +0x16f
runtime.cgoCheckArg(0x7df72b1d62c0, 0x3ec8a16eee50, 0x68?, 0x0, {0x7df72b1ad44c, 0x42})
        /mnt/go/src/runtime/cgocall.go:679 +0x35b
runtime.cgoCheckResult({0x7df72b1d62c0, 0x3ec8a16eee50})
        /mnt/go/src/runtime/cgocall.go:795 +0x4b
_cgoexp_3c910ddb72c4_foo(0x7ffca1b21020)
        /mnt/tmp/parse.go:8 +0x5d
runtime.cgocallbackg1(0x7df72b1a4360, 0x7ffca1b21020, 0x0)
        /mnt/go/src/runtime/cgocall.go:446 +0x289
runtime.cgocallbackg(0x7df72b1a4360, 0x7ffca1b21020, 0x0)
        /mnt/go/src/runtime/cgocall.go:350 +0x132
runtime.cgocallbackg(0x7df72b1a4360, 0x7ffca1b21020, 0x0)
        <autogenerated>:1 +0x2b
runtime.cgocallback(0x0, 0x0, 0x0)
        /mnt/go/src/runtime/asm_amd64.s:1101 +0xcd
runtime.goexit({})
        /mnt/go/src/runtime/asm_amd64.s:1712 +0x1

So doing, fix typos in comments.

Link: https://web.archive.org/web/20251008114504/https://dave.cheney.net/2018/01/08/gos-hidden-pragmas
Suggested-by: Keith Randall khr@golang.org
For #75856

gopherbot · 2025-10-30T12:58:54Z

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gopherbot · 2025-10-30T13:08:51Z

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gopherbot · 2025-10-30T13:08:52Z

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gopherbot · 2025-10-30T13:18:15Z

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gopherbot · 2025-10-30T14:36:17Z

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gopherbot · 2025-10-30T14:46:02Z

This PR (HEAD: eb376d9) has been imported to Gerrit for code review.

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gopherbot · 2025-10-30T14:55:40Z

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gopherbot · 2025-10-31T11:13:18Z

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The title and description of the GitHub PR are used to construct the final commit message.
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gopherbot · 2025-10-31T11:21:19Z

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gopherbot · 2025-10-31T22:06:19Z

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When an unpinned Go pointer (or a pointer to an unpinned Go pointer) is returned from Go to C, 1 package main 2 3 import ( 4 "C" 5 ) 6 7 //export foo 8 func foo(CLine *C.char) string { 9 return C.GoString(CLine) 10 } 11 12 13 func main() { 14 } The error message mentions the file/line of the cgo wrapper, panic: runtime error: cgo result is unpinned Go pointer or points to unpinned Go pointer goroutine 17 [running, locked to thread]: panic({0x798f2341a4c0?, 0xc000112000?}) /usr/lib/go/src/runtime/panic.go:802 +0x168 runtime.cgoCheckArg(0x798f23417e20, 0xc000066e50, 0x0?, 0x0, {0x798f233f5a62, 0x42}) /usr/lib/go/src/runtime/cgocall.go:679 +0x35b runtime.cgoCheckResult({0x798f23417e20, 0xc000066e50}) /usr/lib/go/src/runtime/cgocall.go:795 +0x4b _cgoexp_3c910ddb72c4_foo(0x7ffc9fa9bfa0) _cgo_gotypes.go:65 +0x5d runtime.cgocallbackg1(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0) /usr/lib/go/src/runtime/cgocall.go:446 +0x289 runtime.cgocallbackg(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0) /usr/lib/go/src/runtime/cgocall.go:350 +0x132 runtime.cgocallbackg(0x798f233ec780, 0x7ffc9fa9bfa0, 0x0) <autogenerated>:1 +0x2b runtime.cgocallback(0x0, 0x0, 0x0) /usr/lib/go/src/runtime/asm_amd64.s:1082 +0xcd runtime.goexit({}) /usr/lib/go/src/runtime/asm_amd64.s:1693 +0x1 The cgo wrapper (_cgoexp_3c910ddb72c4_foo) is located in a temporary build artifact (_cgo_gotypes.go) $ go tool cgo -objdir objdir parse.go $ cat -n objdir/_cgo_gotypes.go | sed -n '55,70p' 55 //go:cgo_export_dynamic foo 56 //go:linkname _cgoexp_d48770e267d1_foo _cgoexp_d48770e267d1_foo 57 //go:cgo_export_static _cgoexp_d48770e267d1_foo 58 func _cgoexp_d48770e267d1_foo(a *struct { 59 p0 *_Ctype_char 60 r0 string 61 }) { 62 a.r0 = foo(a.p0) 63 _cgoCheckResult(a.r0) 64 } The file/line of the export'ed function is expected in the error message. Use it in error messages. panic: runtime error: cgo result is unpinned Go pointer or points to unpinned Go pointer goroutine 17 [running, locked to thread]: panic({0x7df72b1d8ae0?, 0x3ec8a1790030?}) /mnt/go/src/runtime/panic.go:877 +0x16f runtime.cgoCheckArg(0x7df72b1d62c0, 0x3ec8a16eee50, 0x68?, 0x0, {0x7df72b1ad44c, 0x42}) /mnt/go/src/runtime/cgocall.go:679 +0x35b runtime.cgoCheckResult({0x7df72b1d62c0, 0x3ec8a16eee50}) /mnt/go/src/runtime/cgocall.go:795 +0x4b _cgoexp_3c910ddb72c4_foo(0x7ffca1b21020) /mnt/tmp/parse.go:8 +0x5d runtime.cgocallbackg1(0x7df72b1a4360, 0x7ffca1b21020, 0x0) /mnt/go/src/runtime/cgocall.go:446 +0x289 runtime.cgocallbackg(0x7df72b1a4360, 0x7ffca1b21020, 0x0) /mnt/go/src/runtime/cgocall.go:350 +0x132 runtime.cgocallbackg(0x7df72b1a4360, 0x7ffca1b21020, 0x0) <autogenerated>:1 +0x2b runtime.cgocallback(0x0, 0x0, 0x0) /mnt/go/src/runtime/asm_amd64.s:1101 +0xcd runtime.goexit({}) /mnt/go/src/runtime/asm_amd64.s:1712 +0x1 So doing, fix typos in comments. Link: https://web.archive.org/web/20251008114504/https://dave.cheney.net/2018/01/08/gos-hidden-pragmas Suggested-by: Keith Randall <khr@golang.org> For golang#75856

gopherbot · 2025-11-01T01:45:00Z

This PR (HEAD: e65839c) has been imported to Gerrit for code review.

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To change your code in response to feedback:
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The title and description of the GitHub PR are used to construct the final commit message.
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See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2025-11-01T01:52:33Z

Message from Ariel Otilibili Anieli:

Patch Set 3:

(3 comments)

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gopherbot · 2025-11-01T10:19:15Z

Message from t hepudds:

Patch Set 4: Commit-Queue+1

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gopherbot · 2025-11-01T10:26:46Z

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Patch Set 4:

Dry run: CV is trying the patch.

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gopherbot · 2025-11-01T10:41:42Z

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Patch Set 4: -Commit-Queue

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gopherbot · 2025-11-01T10:41:43Z

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gopherbot · 2025-11-01T10:41:43Z

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gopherbot · 2025-11-01T11:04:06Z

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Patch Set 4:

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gopherbot · 2025-11-01T13:51:46Z

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Patch Set 4: Code-Review+1

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gopherbot · 2025-11-01T14:28:59Z

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Patch Set 5:

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austinderek mentioned this pull request Oct 30, 2025

cmd/cgo: use the export'ed details in error messages PullRequestInc/go#130

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ariel-anieli force-pushed the cgo-export-orig-func-name branch from 956aa4b to eb376d9 Compare October 30, 2025 14:39

ariel-anieli force-pushed the cgo-export-orig-func-name branch from eb376d9 to 533628d Compare October 31, 2025 11:08

ariel-anieli force-pushed the cgo-export-orig-func-name branch from 533628d to e65839c Compare November 1, 2025 01:40

ariel-anieli changed the title ~~cmd/cgo: use the export'ed details in error messages~~ Nov 1, 2025

ariel-anieli changed the title ~~cmd/cgo: use the export'ed file/line in error messages~~ Nov 1, 2025

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