cgo: fix line/column reporting in syntax error messages

cgo/cgo.go

@@ -391,7 +391,10 @@ func Process(files []*ast.File, dir string, fset *token.FileSet, cflags []string
 
 	// Process all CGo imports.
 	for _, genDecl := range statements {
-		cgoComment := genDecl.Doc.Text()
+		if genDecl.Doc == nil {
+			continue
+		}
+		cgoComment := getCommentText(genDecl.Doc)
 
 		pos := genDecl.Pos()
 		if genDecl.Doc != nil {
@@ -1402,3 +1405,20 @@ func renameFieldName(fieldList *ast.FieldList, name string) {
 	renameFieldName(fieldList, "_"+name)
 	ident.Name = "_" + ident.Name
 }
+
+// getCommentText returns the raw text of an *ast.CommentGroup. It is similar to
+// the Text() method but differs in that it doesn't strip anything and tries to
+// keep all offsets correct by adding spaces and newlines where necessary.
+func getCommentText(g *ast.CommentGroup) string {
+	var text string
+	for _, comment := range g.List {
+		c := comment.Text
+		if c[1] == '/' { /* comment */
+			c = "  " + c[2:]
+		} else { // comment
+			c = "  " + c[2:len(c)-2]
+		}
+		text += c + "\n"
+	}
+	return text
+}

cgo/libclang.go

@@ -81,7 +81,7 @@ func (p *cgoPackage) parseFragment(fragment string, cflags []string, posFilename
 	defer C.free(unsafe.Pointer(filenameC))
 
 	// fix up error locations
-	fragment = fmt.Sprintf("# %d %#v\n", posLine+1, posFilename) + fragment
+	fragment = fmt.Sprintf("# %d %#v\n", posLine, posFilename) + fragment
 
 	fragmentC := C.CString(fragment)
 	defer C.free(unsafe.Pointer(fragmentC))

cgo/testdata/basic.out.go

@@ -13,14 +13,3 @@ type C.uint32_t = uint32
 type C.uint64_t = uint64
 type C.uint8_t = uint8
 type C.uintptr_t = uintptr
-type C.char uint8
-type C.int int32
-type C.long int32
-type C.longlong int64
-type C.schar int8
-type C.short int16
-type C.uchar uint8
-type C.uint uint32
-type C.ulong uint32
-type C.ulonglong uint64
-type C.ushort uint16

cgo/testdata/errors.go

@@ -14,6 +14,9 @@ typedef someType noType; // undefined type
 #define SOME_CONST_2 6) // const not used (so no error)
 #define SOME_CONST_3 1234 // const too large for byte
 */
+//
+//
+// #define SOME_CONST_4 8) // after some empty lines
 import "C"
 
 // Make sure that errors for the following lines won't change with future
@@ -30,4 +33,6 @@ var (
 	_ = C.SOME_CONST_1
 
 	_ byte = C.SOME_CONST_3
+
+	_ = C.SOME_CONST_4
 )

cgo/testdata/errors.out.go

@@ -2,12 +2,14 @@
 //     testdata/errors.go:4:2: warning: some warning
 //     testdata/errors.go:11:9: error: unknown type name 'someType'
 //     testdata/errors.go:13:23: unexpected token ), expected end of expression
+//     testdata/errors.go:19:26: unexpected token ), expected end of expression
 
 // Type checking errors after CGo processing:
 //     testdata/errors.go:102: cannot use 2 << 10 (untyped int constant 2048) as uint8 value in variable declaration (overflows)
 //     testdata/errors.go:105: unknown field z in struct literal
 //     testdata/errors.go:108: undeclared name: C.SOME_CONST_1
 //     testdata/errors.go:110: cannot use C.SOME_CONST_3 (untyped int constant 1234) as byte value in variable declaration (overflows)
+//     testdata/errors.go:112: undeclared name: C.SOME_CONST_4
 
 package main