go.tools/go/loader: enable cgo processing of files that import "C".
Files that import "C" are not valid Go source files and
require preprocessing. Until now, the loader has simply
hard-coded CGO_ENABLED=0 (in effect) which causes go/build to
use build tags select pure Go implementations where they exist
(e.g. in $GOROOT). Where they don't (e.g. arbitrary user
code) this leads to masses of spurious type errors.
(Reported by Guillaume Charmes, private correspondence.)
This change causes the loader to invoke the cgo preprocessor
on such files and to load the preprocessed files instead,
using the original names. This means that the syntax offset
position information is garbage, although thanks to //line
directives, the line numbers at least should be good.
See comment in cgo.go for details.
This CL changes the loader's default behaviour and may make it slower.
CGO_ENABLED=0 enables the old behaviour.
Tested via stdlib_test, which now loads all standard packages
using cgo, and also exercises CGO_ENABLED=0 for "net" and "os/user".
LGTM=gri
R=gri, rsc
CC=golang-codereviews, guillaume.charmes
https://golang.org/cl/86140043
diff --git a/go/loader/loader.go b/go/loader/loader.go
index 04b54cb..534cfd1 100644
--- a/go/loader/loader.go
+++ b/go/loader/loader.go
@@ -186,6 +186,11 @@
// If Build is non-nil, it is used to locate source packages.
// Otherwise &build.Default is used.
+ //
+ // By default, cgo is invoked to preprocess Go files that
+ // import the fake package "C". This behaviour can be
+ // disabled by setting CGO_ENABLED=0 in the environment prior
+ // to startup, or by setting Build.CgoEnabled=false.
Build *build.Context
// If DisplayPath is non-nil, it is used to transform each
@@ -612,18 +617,15 @@
// then loads, parses and returns them.
//
// 'which' indicates which files to include:
-// 'g': include non-test *.go source files (GoFiles)
+// 'g': include non-test *.go source files (GoFiles + processed CgoFiles)
// 't': include in-package *_test.go source files (TestGoFiles)
// 'x': include external *_test.go source files. (XTestGoFiles)
//
+// TODO(adonovan): don't fail just because some files contain parse errors.
+//
func (conf *Config) parsePackageFiles(path string, which rune) ([]*ast.File, error) {
- // Set the "!cgo" go/build tag, preferring (dummy) Go to
- // native C implementations of net.cgoLookupHost et al.
- ctxt := *conf.build() // copy
- ctxt.CgoEnabled = false
-
// Import(srcDir="") disables local imports, e.g. import "./foo".
- bp, err := ctxt.Import(path, "", 0)
+ bp, err := conf.build().Import(path, "", 0)
if _, ok := err.(*build.NoGoError); ok {
return nil, nil // empty directory
}
@@ -642,7 +644,22 @@
default:
panic(which)
}
- return parseFiles(conf.fset(), &ctxt, conf.DisplayPath, bp.Dir, filenames, conf.ParserMode)
+
+ files, err := parseFiles(conf.fset(), conf.build(), conf.DisplayPath, bp.Dir, filenames, conf.ParserMode)
+ if err != nil {
+ return nil, err
+ }
+
+ // Preprocess CgoFiles and parse the outputs (sequentially).
+ if which == 'g' && bp.CgoFiles != nil {
+ cgofiles, err := processCgoFiles(bp, conf.fset(), conf.ParserMode)
+ if err != nil {
+ return nil, err
+ }
+ files = append(files, cgofiles...)
+ }
+
+ return files, nil
}
// doImport imports the package denoted by path.
