golang/go · error · PackageError

Objective-C source files not allowed when not using cgo or S

Error message

Objective-C source files not allowed when not using cgo or SWIG: %s

What it means

A Go package contains Objective-C source files (.m) but neither cgo nor SWIG is active. Like the C++ check, this restriction applies to all compiler toolchains. The check is len(p.MFiles) > 0 && !p.UsesCgo() && !p.UsesSwig(). Objective-C files are typically used for macOS/iOS framework integration.

Source

Thrown at src/cmd/go/internal/load/pkg.go:2115

		// and HFiles are okay (they might be used by the SFiles).
		// Also Sysofiles are okay (they might not contain object
		// code; see issue #16050).
	}

	// The gc toolchain only permits C source files with cgo or SWIG.
	if len(p.CFiles) > 0 && !p.UsesCgo() && !p.UsesSwig() && cfg.BuildContext.Compiler == "gc" {
		setError(fmt.Errorf("C source files not allowed when not using cgo or SWIG: %s", strings.Join(p.CFiles, " ")))
		return
	}

	// C++, Objective-C, and Fortran source files are permitted only with cgo or SWIG,
	// regardless of toolchain.
	if len(p.CXXFiles) > 0 && !p.UsesCgo() && !p.UsesSwig() {
		setError(fmt.Errorf("C++ source files not allowed when not using cgo or SWIG: %s", strings.Join(p.CXXFiles, " ")))
		return
	}
	if len(p.MFiles) > 0 && !p.UsesCgo() && !p.UsesSwig() {
		setError(fmt.Errorf("Objective-C source files not allowed when not using cgo or SWIG: %s", strings.Join(p.MFiles, " ")))
		return
	}
	if len(p.FFiles) > 0 && !p.UsesCgo() && !p.UsesSwig() {
		setError(fmt.Errorf("Fortran source files not allowed when not using cgo or SWIG: %s", strings.Join(p.FFiles, " ")))
		return
	}
}

// An EmbedError indicates a problem with a go:embed directive.
type EmbedError struct {
	Pattern string
	Err     error
}

func (e *EmbedError) Error() string {
	return fmt.Sprintf("pattern %s: %v", e.Pattern, e.Err)
}

View on GitHub (pinned to b6b368adc5)

Solutions

  1. Enable cgo and add a proper // #cgo preamble in a .go file that wraps the Objective-C code.
  2. Ensure CGO_ENABLED=1, especially on macOS (go env CGO_ENABLED).
  3. Remove .m files if Objective-C integration is not needed for the current build target.
  4. Consider SWIG for complex Objective-C framework bridging.

Example fix

// before — .m file present but no cgo
// mypackage/
//   main.go
//   delegate.m

// after — add cgo wrapping ObjC code
// mypackage/main.go
package main

/*
#cgo darwin LDFLAGS: -framework Foundation
#import <Foundation/Foundation.h>
#include "delegate.h"
*/
import "C"
// mypackage/delegate.m remains
Defensive patterns

Strategy: validation

Validate before calling

// Check that Objective-C files are accompanied by cgo or SWIG before building.
func checkObjcCgoRequirement(pkgDir string) error {
    entries, _ := os.ReadDir(pkgDir)
    var hasM, hasCgo, hasSwig bool
    for _, e := range entries {
        name := e.Name()
        if strings.HasSuffix(name, ".m") {
            hasM = true
        }
        if strings.HasSuffix(name, ".swig") || strings.HasSuffix(name, ".swigcxx") {
            hasSwig = true
        }
        if strings.HasSuffix(name, ".go") {
            data, _ := os.ReadFile(filepath.Join(pkgDir, name))
            if bytes.Contains(data, []byte("import \"C\"")) {
                hasCgo = true
            }
        }
    }
    if hasM && !hasCgo && !hasSwig {
        return fmt.Errorf("Objective-C files present without cgo or SWIG")
    }
    return nil
}

Prevention

When it happens

Trigger: Adding .m files to a package directory without setting up cgo or SWIG integration. Having leftover Objective-C files from a previous macOS-specific build configuration. Cross-compiling away from macOS while .m files remain in the source tree.

Common situations: Integrating macOS frameworks (Foundation, UIKit, AppKit) via Objective-C without proper cgo setup. Accidental inclusion of .m files in a cross-platform package. Removing cgo integration but forgetting to delete .m files. Third-party macOS bindings that ship .m files.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/f46b9f75ac882cbb. Report an issue: GitHub.