[release-branch.go1.9] 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>
Reviewed-on: https://go-review.googlesource.com/70975
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

7 files changed, 43 insertions, 18 deletions

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 7a1ea2707c..54c48434cc 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -41,7 +41,7 @@ func parseFiles(filenames []string) uint {
 			}
 			defer f.Close()
 
-			p.file, _ = syntax.Parse(base, f, p.error, p.pragma, syntax.CheckBranches) // errors are tracked via p.error
+			p.file, _ = syntax.Parse(base, f, p.error, p.pragma, fileh, syntax.CheckBranches) // errors are tracked via p.error
 		}(filename)
 	}
 
@@ -70,6 +70,10 @@ func yyerrorpos(pos src.Pos, format string, args ...interface{}) {
 
 var pathPrefix string
 
+func fileh(name string) string {
+	return objabi.AbsFile("", name, pathPrefix)
+}
+
 func absFilename(name string) string {
 	return objabi.AbsFile(Ctxt.Pathname, name, pathPrefix)
 }
diff --git a/src/cmd/compile/internal/syntax/nodes_test.go b/src/cmd/compile/internal/syntax/nodes_test.go
index be9d5d897c..1bba9eeacf 100644
--- a/src/cmd/compile/internal/syntax/nodes_test.go
+++ b/src/cmd/compile/internal/syntax/nodes_test.go
@@ -291,7 +291,7 @@ func testPos(t *testing.T, list []test, prefix, suffix string, extract func(*Fil
 		}
 
 		// build syntaxt tree
-		file, err := ParseBytes(nil, []byte(src), nil, nil, 0)
+		file, err := ParseBytes(nil, []byte(src), nil, nil, nil, 0)
 		if err != nil {
 			t.Errorf("parse error: %s: %v (%s)", src, err, test.nodetyp)
 			continue
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index bcf56d5faa..b9129b0d9c 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -16,9 +16,10 @@ const debug = false
 const trace = false
 
 type parser struct {
-	base *src.PosBase
-	errh ErrorHandler
-	mode Mode
+	base  *src.PosBase
+	errh  ErrorHandler
+	fileh FilenameHandler
+	mode  Mode
 	scanner
 
 	first  error  // first error encountered
@@ -29,9 +30,10 @@ type parser struct {
 	indent []byte // tracing support
 }
 
-func (p *parser) init(base *src.PosBase, r io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) {
+func (p *parser) init(base *src.PosBase, r io.Reader, errh ErrorHandler, pragh PragmaHandler, fileh FilenameHandler, mode Mode) {
 	p.base = base
 	p.errh = errh
+	p.fileh = fileh
 	p.mode = mode
 	p.scanner.init(
 		r,
@@ -76,7 +78,11 @@ func (p *parser) updateBase(line, col uint, text string) {
 		p.error_at(p.pos_at(line, col+uint(i+1)), "invalid line number: "+nstr)
 		return
 	}
-	p.base = src.NewLinePragmaBase(src.MakePos(p.base.Pos().Base(), line, col), text[:i], uint(n))
+	absFile := text[:i]
+	if p.fileh != nil {
+		absFile = p.fileh(absFile)
+	}
+	p.base = src.NewLinePragmaBase(src.MakePos(p.base.Pos().Base(), line, col), absFile, uint(n))
 }
 
 func (p *parser) got(tok token) bool {
diff --git a/src/cmd/compile/internal/syntax/parser_test.go b/src/cmd/compile/internal/syntax/parser_test.go
index 4c317dab60..0478088ec8 100644
--- a/src/cmd/compile/internal/syntax/parser_test.go
+++ b/src/cmd/compile/internal/syntax/parser_test.go
@@ -131,7 +131,7 @@ func verifyPrint(filename string, ast1 *File) {
 		panic(err)
 	}
 
-	ast2, err := ParseBytes(src.NewFileBase(filename, filename), buf1.Bytes(), nil, nil, 0)
+	ast2, err := ParseBytes(src.NewFileBase(filename, filename), buf1.Bytes(), nil, nil, nil, 0)
 	if err != nil {
 		panic(err)
 	}
@@ -155,7 +155,7 @@ func verifyPrint(filename string, ast1 *File) {
 }
 
 func TestIssue17697(t *testing.T) {
-	_, err := ParseBytes(nil, nil, nil, nil, 0) // return with parser error, don't panic
+	_, err := ParseBytes(nil, nil, nil, nil, nil, 0) // return with parser error, don't panic
 	if err == nil {
 		t.Errorf("no error reported")
 	}
@@ -199,8 +199,16 @@ func TestLineDirectives(t *testing.T) {
 		// test effect of //line directive on (relative) position information
 		{"//line foo:123\n   foo", "syntax error: package statement must be first", "foo", 123 - linebase, 3},
 		{"//line foo:123\n//line bar:345\nfoo", "syntax error: package statement must be first", "bar", 345 - linebase, 0},
+
+		{"//line " + runtime.GOROOT() + "/src/a/a.go:123\n   foo", "syntax error: package statement must be first", "$GOROOT/src/a/a.go", 123 - linebase, 3},
 	} {
-		_, err := ParseBytes(nil, []byte(test.src), nil, nil, 0)
+		fileh := func(name string) string {
+			if strings.HasPrefix(name, runtime.GOROOT()) {
+				return "$GOROOT" + name[len(runtime.GOROOT()):]
+			}
+			return name
+		}
+		_, err := ParseBytes(nil, []byte(test.src), nil, nil, fileh, 0)
 		if err == nil {
 			t.Errorf("%s: no error reported", test.src)
 			continue
diff --git a/src/cmd/compile/internal/syntax/printer_test.go b/src/cmd/compile/internal/syntax/printer_test.go
index 14652f4ac6..bbf75a957d 100644
--- a/src/cmd/compile/internal/syntax/printer_test.go
+++ b/src/cmd/compile/internal/syntax/printer_test.go
@@ -29,7 +29,7 @@ func TestPrintString(t *testing.T) {
 		"package p; type _ = int; type T1 = struct{}; type ( _ = *struct{}; T2 = float32 )",
 		// TODO(gri) expand
 	} {
-		ast, err := ParseBytes(nil, []byte(want), nil, nil, 0)
+		ast, err := ParseBytes(nil, []byte(want), nil, nil, nil, 0)
 		if err != nil {
 			t.Error(err)
 			continue
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)
 }
diff --git a/src/cmd/internal/objabi/line.go b/src/cmd/internal/objabi/line.go
index ed509b7001..1c671b211f 100644
--- a/src/cmd/internal/objabi/line.go
+++ b/src/cmd/internal/objabi/line.go
@@ -44,7 +44,7 @@ func AbsFile(dir, file, pathPrefix string) string {
 		abs = "??"
 	}
 
-	return filepath.Clean(abs)
+	return abs
 }
 
 // Does s have t as a path prefix?