[release-branch.go1.19] cmd/cgo: error out if the source path used in line directives would contain a newline

cmd/cgo uses '//line' directives to map generated source
files back to the original source file and line nmubers.

The line directives have no way to escape newline characters,
so cmd/cgo must not be used if the line directives would contain
such characters.

Updates #60515.
Updates #60167.

Change-Id: I8581cea74d6c08f82e86ed87127e81252e1bf78c
Reviewed-on: https://go-review.googlesource.com/c/go/+/501576
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
(cherry picked from commit c48228312e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/501821
TryBot-Bypass: Bryan Mills <bcmills@google.com>

src/cmd/cgo/ast.go

@@ -80,6 +80,11 @@ func (f *File) ParseGo(abspath string, src []byte) {
 				cg = d.Doc
 			}
 			if cg != nil {
+				if strings.ContainsAny(abspath, "\r\n") {
+					// This should have been checked when the file path was first resolved,
+					// but we double check here just to be sure.
+					fatalf("internal error: ParseGo: abspath contains unexpected newline character: %q", abspath)
+				}
 				f.Preamble += fmt.Sprintf("#line %d %q\n", sourceLine(cg), abspath)
 				f.Preamble += commentText(cg) + "\n"
 				f.Preamble += "#line 1 \"cgo-generated-wrapper\"\n"

src/cmd/cgo/main.go

@@ -357,6 +357,12 @@ func main() {
 
 		// Apply trimpath to the file path. The path won't be read from after this point.
 		input, _ = objabi.ApplyRewrites(input, *trimpath)
+		if strings.ContainsAny(input, "\r\n") {
+			// ParseGo, (*Package).writeOutput, and printer.Fprint in SourcePos mode
+			// all emit line directives, which don't permit newlines in the file path.
+			// Bail early if we see anything newline-like in the trimmed path.
+			fatalf("input path contains newline character: %q", input)
+		}
 		goFiles[i] = input
 
 		f := new(File)

src/cmd/cgo/out.go

@@ -642,6 +642,11 @@ func (p *Package) writeOutput(f *File, srcfile string) {
 
 	// Write Go output: Go input with rewrites of C.xxx to _C_xxx.
 	fmt.Fprintf(fgo1, "// Code generated by cmd/cgo; DO NOT EDIT.\n\n")
+	if strings.ContainsAny(srcfile, "\r\n") {
+		// This should have been checked when the file path was first resolved,
+		// but we double check here just to be sure.
+		fatalf("internal error: writeOutput: srcfile contains unexpected newline character: %q", srcfile)
+	}
 	fmt.Fprintf(fgo1, "//line %s:1:1\n", srcfile)
 	fgo1.Write(f.Edit.Bytes())
 

src/cmd/go/testdata/script/build_cwd_newline.txt

@@ -43,6 +43,19 @@ stderr 'package example: invalid package directory .*uh-oh'
 ! stdout .
 ! exists obj_
 
+# The cgo tool should only accept the source file if the working directory
+# is not written in line directives in the resulting files.
+
+[cgo] ! go tool cgo main.go
+[cgo] stderr 'cgo: input path contains newline character: .*uh-oh'
+[cgo] ! exists _obj
+
+[cgo] go tool cgo -trimpath=$PWD main.go
+[cgo] grep '//line main\.go:1:1' _obj/main.cgo1.go
+[cgo] ! grep 'uh-oh' _obj/main.cgo1.go
+[cgo] rm _obj
+
+
 # Since we do preserve $PWD (or set it appropriately) for commands, and we do
 # not resolve symlinks unnecessarily, referring to the contents of the unsafe
 # directory via a safe symlink should be ok, and should not inject the data from
@@ -92,6 +105,9 @@ go test -v .
 ! stderr panic
 stdout '^ok$'  # 'go test' combines the test's stdout into stderr
 
+[cgo] go tool cgo main.go
+[cgo] grep '//line .*'${/}'link'${/}'main\.go:1:1' _obj/main.cgo1.go
+[cgo] ! grep 'uh-oh' _obj/main.cgo1.go
 
 -- $WORK/go.mod --
 module example