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cmd/go: go install doesn't recognize changes to c code in another directory #19883

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alexd765 opened this issue Apr 7, 2017 · 3 comments
Closed

cmd/go: go install doesn't recognize changes to c code in another directory #19883

alexd765 opened this issue Apr 7, 2017 · 3 comments
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@alexd765
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alexd765 commented Apr 7, 2017

Please answer these questions before submitting your issue. Thanks!

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

go version devel +a8b2e4a Fri Mar 31 21:24:09 2017 +0000 linux/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/alex/gopath"
GORACE=""
GOROOT="/home/alex/go"
GOTOOLDIR="/home/alex/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build681403283=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

  • go install -v program with c code
  • make changes to c code in different directory
  • go install -v again

If possible, provide a recipe for reproducing the error.

cat main.go:
package main

import "fmt"

/*
#include "test/test.h"
*/
import "C"

func main() {
	fmt.Println(C.x)
}

cat test/test.h:
int x=1;

on github

What did you expect to see?

go install -v
github.com/alexd765/cgo-issue

change to x=2 in test/test.h

go install -v
github.com/alexd765/cgo-issue

What did you see instead?

go install -v
github.com/alexd765/cgo-issue

change to x=2 in test/test.h

go install -v
  • go install thinks the code didn't change.
  • It works if the c code is in the same directory.
  • it doesn't work if the c code is in another directory (outside or subdirectory).
@alexd765 alexd765 changed the title cmd/go: go install doesn't recognise changes in c code in different directories cmd/go: go install doesn't recognize changes to c code in different directories Apr 7, 2017
@alexd765 alexd765 changed the title cmd/go: go install doesn't recognize changes to c code in different directories cmd/go: go install doesn't recognize changes to c code in another directory Apr 7, 2017
@bradfitz bradfitz added this to the Unplanned milestone Apr 9, 2017
@bradfitz
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bradfitz commented Apr 9, 2017

Of note: cmd/go is a Go build system and not a C build system. But I'll let @rsc decide what to do here, if anything.

@alexd765
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That makes sense.

This is obviously a minimal example. I want to give a little bit more context how I ran into this:

We have a not-so-thin wrapper around a C library that is a mix of Go and C code that we install with go install (without the -v). When we make changes to go code and c code at the same time everything works.
When we made only changes to the C Code it was quite surprising that the new version didn't get installed.

The workaround is to force rebuilding with go install -a.

@rsc
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rsc commented Apr 10, 2017

The Go command essentially requires that your C code be in the same directory as the Go package using it, not in a subdirectory or other directory. This is by design: package directories are meant to be completely self-contained, although obviously this is difficult/impossible to enforce in all cases.

@rsc rsc closed this as completed Apr 10, 2017
@golang golang locked and limited conversation to collaborators Apr 10, 2018
@rsc rsc removed their assignment Jun 23, 2022
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