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elagergren-spideroak opened this issue Feb 17, 2021 · 5 comments
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runtime/cgo: cannot build with -Wsign-compare #44340

elagergren-spideroak opened this issue Feb 17, 2021 · 5 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.17

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@elagergren-spideroak
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elagergren-spideroak commented Feb 17, 2021 •
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What version of Go are you using (go version)?

$ go version
go version go1.16 linux/amd64
$ gcc version
gcc (Debian 8.3.0-6) 8.3.0

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="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16"
GCCGO="gccgo"
AR="llvm-ar-11"
CC="clang-11"
CXX="clang++-11"
CGO_ENABLED="1"
GOMOD="/dev/null"
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=/tmp/go-build291458045=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ cat x.go
package main

/*
#include <stdio.h>
static inline void hello() {
	puts("hello, world!");
}
*/
import "C"

func main() {
	C.hello()
}
$ CGO_CFLAGS="$(go env CGO_CFLAGS) -Wsign-compare" go build x.go

What did you expect to see?

Successful compilation.

What did you see instead?

# runtime/cgo
linux_syscall.c:42:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:47:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:52:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:57:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:62:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:67:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:73:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:79:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
linux_syscall.c:84:2: error: comparison of integers of different signs: 'uintptr_t' (aka 'unsigned long') and 'int' [-Werror,-Wsign-compare]
linux_syscall.c:35:11: note: expanded from macro 'SET_RETVAL'
@seankhliao seankhliao added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Feb 17, 2021
@gopherbot
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Change https://golang.org/cl/293209 mentions this issue: runtime/cgo: add cast in C code to avoid C compiler warning

@ianlancetaylor
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@gopherbot Please open backport to 1.16.

This problem makes it hard to build 1.16 programs that use cgo if you want to use -Wsign-compare in CGO_CFLAGS (to check your own C code). The CL fixes the problem.

@gopherbot gopherbot mentioned this issue Feb 17, 2021
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@gopherbot
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Backport issue(s) opened: #44346 (for 1.16).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.

@elagergren-spideroak
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@ianlancetaylor thanks.

@gopherbot
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Change https://golang.org/cl/293411 mentions this issue: [release-branch.go1.16] runtime/cgo: add cast in C code to avoid C compiler warning

gopherbot pushed a commit that referenced this issue Feb 18, 2021
@ianlancetaylor
[release-branch.go1.16] runtime/cgo: add cast in C code to avoid C co…
1a7e9af 
…mpiler warning

For #44340
Fixes #44346

Change-Id: Id80dd1f44a988b653933732afcc8e49a826affc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/293209
Reviewed-by: Andrew G. Morgan <agm@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
(cherry picked from commit 07ef313)
Reviewed-on: https://go-review.googlesource.com/c/go/+/293411
TryBot-Result: Go Bot <gobot@golang.org>
@toothrot toothrot added this to the Go1.17 milestone Feb 18, 2021
@dmitshur dmitshur added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Feb 18, 2021
@golang golang locked and limited conversation to collaborators Feb 18, 2022
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