Disable CGo when loading packages.

nevkontakte · nevkontakte · commit 49f2893b27d5 · 2022-04-19T11:29:32.000+01:00
GopherJS doesn't support CGo. This was originally enabled to address gopherjs#215 by providing a better error when attempting to build a CGo package (instead of a compiler panic). However, this approach makes GopherJS refuse to build packages, which have a CGo and purego versions guarded by the `cgo` build tag: GopherJS woudl try to load the cgo version and error out. After this change GopherJS won't attempt to load Go sources with `import "C"`, and it will load sources with `//go:build !cgo` instead. For packages that require CGo one of the following errors will be returned: - "No buildable sources" if all Go sources import C. - "Undefined symbol" for symbols defined in the Go sources that import C and that are referenced by other Go source files. - "Unknown import path C" if you try to `gopherjs run` a source with import C directly.
diff --git a/build/build.go b/build/build.go
@@ -47,16 +47,6 @@ var DefaultGOROOT = func() string {
 	return build.Default.GOROOT
 }()
 
-// ImportCError is returned when GopherJS attempts to build a package that uses
-// CGo.
-type ImportCError struct {
-	pkgPath string
-}
-
-func (e *ImportCError) Error() string {
-	return e.pkgPath + `: importing "C" is not supported by GopherJS`
-}
-
 // NewBuildContext creates a build context for building Go packages
 // with GopherJS compiler.
 //
diff --git a/build/context.go b/build/context.go
@@ -98,10 +98,6 @@ func (sc simpleCtx) Import(importPath string, srcDir string, mode build.ImportMo
 	}
 	pkg = sc.applyPostloadTweaks(pkg)
 
-	if len(pkg.CgoFiles) > 0 {
-		return nil, &ImportCError{pkg.ImportPath}
-	}
-
 	return &PackageData{
 		Package:   pkg,
 		IsVirtual: sc.isVirtual,
@@ -224,10 +220,6 @@ func (sc simpleCtx) applyPreloadTweaks(importPath string, srcDir string, mode bu
 		bctx.GOARCH = "wasm"
 	}
 	switch importPath {
-	case "crypto/x509", "os/user":
-		// These stdlib packages have cgo and non-cgo versions (via build tags); we
-		// want the latter.
-		bctx.CgoEnabled = false
 	case "github.com/gopherjs/gopherjs/js", "github.com/gopherjs/gopherjs/nosync":
 		// These packages are already embedded via gopherjspkg.FS virtual filesystem
 		// (which can be safely vendored). Don't try to use vendor directory to
@@ -342,7 +334,7 @@ func goCtx(e Env) *simpleCtx {
 			InstallSuffix: e.InstallSuffix,
 			Compiler:      "gc",
 			BuildTags:     append(append([]string{}, e.BuildTags...), defaultBuildTags...),
-			CgoEnabled:    true, // detect `import "C"` to throw proper error
+			CgoEnabled:    false, // CGo is not supported by GopherJS.
 
 			// go/build supports modules, but only when no FS access functions are
 			// overridden and when provided ReleaseTags match those of the default
diff --git a/compiler/linkname.go b/compiler/linkname.go
@@ -101,15 +101,6 @@ func parseGoLinknames(fset *token.FileSet, pkgPath string, file *ast.File) ([]Go
 
 		obj := file.Scope.Lookup(localName)
 		if obj == nil {
-			if pkgPath == "syscall" {
-				// Syscall uses go:cgo_import_dynamic pragma to import symbols from
-				// dynamic libraries when build with GOOS=darwin, which GopherJS doesn't
-				// support. Silently ignore such directives.
-				//
-				// In the long term https://github.com/gopherjs/gopherjs/issues/693 is a
-				// preferred solution.
-				return nil
-			}
 			return fmt.Errorf("//go:linkname local symbol %q is not found in the current source file", localName)
 		}
 
