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C.free(unsafe.Pointer(cs)) returns "could not determine kind of name for C.free" #39871

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yusufbuyruk opened this issue Jun 26, 2020 · 2 comments
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@yusufbuyruk
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@yusufbuyruk yusufbuyruk commented Jun 26, 2020

I have copied this code from https://golang.org/cmd/cgo/
`package main

import "C"
import "unsafe"

func main() {
cs := C.CString("Hello from stdio")
C.myprint(cs)
C.free(unsafe.Pointer(cs))
}`

And here is my code
`package main

import "C"
import "unsafe"
import "fmt"

func main() {
s := "Hello World!"
cs := C.CString(s)
C.free(unsafe.Pointer(cs))
fmt.Println(s)
}`

Returns compiler error: "could not determine kind of name for C.free"

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

$ go version
go version go1.14.3 windows/amd64

Does this issue reproduce with the latest release?

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

go env Output
$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\yusuf\AppData\Local\go-build
set GOENV=C:\Users\yusuf\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\yusuf\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\yusuf\AppData\Local\Temp\go-build313812094=/tmp/go-build -gno-record-gcc-switches
PS C:\Users\yusuf\Desktop\cfree-compiler-error>

What did you do?

`package main

import "C"
import "unsafe"
import "fmt"

func main() {
s := "Hello World!"
cs := C.CString(s)
C.free(unsafe.Pointer(cs))
fmt.Println(s)
}`

What did you expect to see?

"Hello World!"

What did you see instead?

compiler error: "could not determine kind of name for C.free"

@mattn
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@mattn mattn commented Jun 26, 2020

C.free can be used with include stdlib.h. Please try this:

package main

/*
#include <stdlib.h>
*/
import "C"
import "unsafe"
import "fmt"

func main() {
    s := "Hello World!"
    cs := C.CString(s)
    C.free(unsafe.Pointer(cs))
    fmt.Println(s)
}

If you want to use Windows APIs, you should #include <windows.h> instead.

@yusufbuyruk
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@yusufbuyruk yusufbuyruk commented Jun 26, 2020

@mattn
Thank you very much. Problem solved.

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