cmd/compile: replace GOROOT in //line directives

The compiler replaces any path of the form /path/to/goroot/src/net/port.go
with GOROOT/src/net/port.go so that the same object file is
produced if the GOROOT is moved. It was skipping this transformation
for any absolute path into the GOROOT that came from //line directives,
such as those generated by cmd/cgo.

Fixes #21373
Fixes #21720
Fixes #21825

Change-Id: I2784c701b4391cfb92e23efbcb091a84957d61dd
Reviewed-on: https://go-review.googlesource.com/63693
Run-TryBot: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 13 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/syntax/syntax.go b/src/cmd/compile/internal/syntax/syntax.go
index ed5e254724..f58d5efd29 100644
--- a/src/cmd/compile/internal/syntax/syntax.go
+++ b/src/cmd/compile/internal/syntax/syntax.go
@@ -39,11 +39,15 @@ type ErrorHandler func(err error)
 // appropriate.
 type Pragma uint16
 
-// A PragmaHandler is used to process //line and //go: directives as
+// A PragmaHandler is used to process //go: directives as
 // they're scanned. The returned Pragma value will be unioned into the
 // next FuncDecl node.
 type PragmaHandler func(pos src.Pos, text string) Pragma
 
+// A FilenameHandler is used to process each filename encountered
+// in //line directives. The returned value is used as the absolute filename.
+type FilenameHandler func(name string) string
+
 // Parse parses a single Go source file from src and returns the corresponding
 // syntax tree. If there are errors, Parse will return the first error found,
 // and a possibly partially constructed syntax tree, or nil if no correct package
@@ -55,8 +59,11 @@ type PragmaHandler func(pos src.Pos, text string) Pragma
 //
 // If a PragmaHandler is provided, it is called with each pragma encountered.
 //
+// If a FilenameHandler is provided, it is called to process each filename
+// encountered in //line directives.
+//
 // The Mode argument is currently ignored.
-func Parse(base *src.PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) (_ *File, first error) {
+func Parse(base *src.PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHandler, fileh FilenameHandler, mode Mode) (_ *File, first error) {
 	defer func() {
 		if p := recover(); p != nil {
 			if err, ok := p.(Error); ok {
@@ -68,14 +75,14 @@ func Parse(base *src.PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHand
 	}()
 
 	var p parser
-	p.init(base, src, errh, pragh, mode)
+	p.init(base, src, errh, pragh, fileh, mode)
 	p.next()
 	return p.fileOrNil(), p.first
 }
 
 // ParseBytes behaves like Parse but it reads the source from the []byte slice provided.
-func ParseBytes(base *src.PosBase, src []byte, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
-	return Parse(base, &bytesReader{src}, errh, pragh, mode)
+func ParseBytes(base *src.PosBase, src []byte, errh ErrorHandler, pragh PragmaHandler, fileh FilenameHandler, mode Mode) (*File, error) {
+	return Parse(base, &bytesReader{src}, errh, pragh, fileh, mode)
 }
 
 type bytesReader struct {
@@ -101,5 +108,5 @@ func ParseFile(filename string, errh ErrorHandler, pragh PragmaHandler, mode Mod
 		return nil, err
 	}
 	defer f.Close()
-	return Parse(src.NewFileBase(filename, filename), f, errh, pragh, mode)
+	return Parse(src.NewFileBase(filename, filename), f, errh, pragh, nil, mode)
 }