golang/go

cmd/cgo: warning: built-in function ‘free’ declared as non-function

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#32,411 opened on Jun 3, 2019

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Description

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

Does this issue reproduce with the latest release?

Yes.

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

What did you do?

go run the following program that is using C.free as a value. (In actual code, it’s passed to a foo_set_free_fun(void (*)(void *)).) The warning is not emit when calling C.free(), nor is it when e.g. printing the address of C.getenv.

package main

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

func main() {
        fmt.Printf("%#v\n", C.free)
}

What did you expect to see?

What did you see instead?

Contributor guide

Research direction
Investigate how cgo generates wrapper code for C.free and why it triggers a GCC warning about built in function 'free' declared as non function. Look into the cgo source code in src/cmd/cgo/ and understand how it handles C function pointers, especially for functions like free that are built in in GCC. Find a way to suppress or fix the warning, possibly by modifying the generated C code or by using pragmas.
Tech stack
go
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Gocgo
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65