cmd/cgo: use a plausible position for typedef error messages

Fixes #28069

Change-Id: I7e0f96b8b6d123de283325fcb78ec76455050f6d
Reviewed-on: https://go-review.googlesource.com/c/152158
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

misc/cgo/errors/errors_test.go

@@ -126,7 +126,12 @@ func TestReportsTypeErrors(t *testing.T) {
 	}
 
 	if sizeofLongDouble(t) > 8 {
-		check(t, "err4.go")
+		for _, file := range []string{
+			"err4.go",
+			"issue28069.go",
+		} {
+			check(t, file)
+		}
 	}
 }
 

misc/cgo/errors/src/issue28069.go

@@ -0,0 +1,26 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that the error message for an unrepresentable typedef in a
+// union appears on the right line. This test is only run if the size
+// of long double is larger than 64.
+
+package main
+
+/*
+typedef long double             Float128;
+
+typedef struct SV {
+    union {
+        Float128         float128;
+    } value;
+} SV;
+*/
+import "C"
+
+type ts struct {
+	tv *C.SV // ERROR HERE
+}
+
+func main() {}

src/cmd/cgo/gcc.go

@@ -171,11 +171,13 @@ func (p *Package) Translate(f *File) {
 	for len(p.typedefs) > numTypedefs {
 		numTypedefs = len(p.typedefs)
 		// Also ask about any typedefs we've seen so far.
-		for _, a := range p.typedefList {
+		for _, info := range p.typedefList {
-			f.Name[a] = &Name{
+			n := &Name{
-				Go: a,
+				Go: info.typedef,
-				C:  a,
+				C:  info.typedef,
 			}
+			f.Name[info.typedef] = n
+			f.NamePos[n] = info.pos
 		}
 		needType := p.guessKinds(f)
 		if len(needType) > 0 {
@@ -573,7 +575,7 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 				fatalf("malformed __cgo__ name: %s", name)
 			}
 			types[i] = t.Type
-			p.recordTypedefs(t.Type)
+			p.recordTypedefs(t.Type, f.NamePos[names[i]])
 		}
 		if e.Tag != dwarf.TagCompileUnit {
 			r.SkipChildren()
@@ -641,10 +643,11 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 }
 
 // recordTypedefs remembers in p.typedefs all the typedefs used in dtypes and its children.
-func (p *Package) recordTypedefs(dtype dwarf.Type) {
+func (p *Package) recordTypedefs(dtype dwarf.Type, pos token.Pos) {
-	p.recordTypedefs1(dtype, map[dwarf.Type]bool{})
+	p.recordTypedefs1(dtype, pos, map[dwarf.Type]bool{})
 }
-func (p *Package) recordTypedefs1(dtype dwarf.Type, visited map[dwarf.Type]bool) {
+
+func (p *Package) recordTypedefs1(dtype dwarf.Type, pos token.Pos, visited map[dwarf.Type]bool) {
 	if dtype == nil {
 		return
 	}
@@ -660,23 +663,23 @@ func (p *Package) recordTypedefs1(dtype dwarf.Type, visited map[dwarf.Type]bool)
 		}
 		if !p.typedefs[dt.Name] {
 			p.typedefs[dt.Name] = true
-			p.typedefList = append(p.typedefList, dt.Name)
+			p.typedefList = append(p.typedefList, typedefInfo{dt.Name, pos})
-			p.recordTypedefs1(dt.Type, visited)
+			p.recordTypedefs1(dt.Type, pos, visited)
 		}
 	case *dwarf.PtrType:
-		p.recordTypedefs1(dt.Type, visited)
+		p.recordTypedefs1(dt.Type, pos, visited)
 	case *dwarf.ArrayType:
-		p.recordTypedefs1(dt.Type, visited)
+		p.recordTypedefs1(dt.Type, pos, visited)
 	case *dwarf.QualType:
-		p.recordTypedefs1(dt.Type, visited)
+		p.recordTypedefs1(dt.Type, pos, visited)
 	case *dwarf.FuncType:
-		p.recordTypedefs1(dt.ReturnType, visited)
+		p.recordTypedefs1(dt.ReturnType, pos, visited)
 		for _, a := range dt.ParamType {
-			p.recordTypedefs1(a, visited)
+			p.recordTypedefs1(a, pos, visited)
 		}
 	case *dwarf.StructType:
 		for _, f := range dt.Field {
-			p.recordTypedefs1(f.Type, visited)
+			p.recordTypedefs1(f.Type, pos, visited)
 		}
 	}
 }

src/cmd/cgo/main.go

@@ -47,7 +47,14 @@ type Package struct {
 	GccFiles    []string        // list of gcc output files
 	Preamble    string          // collected preamble for _cgo_export.h
 	typedefs    map[string]bool // type names that appear in the types of the objects we're interested in
-	typedefList []string
+	typedefList []typedefInfo
+}
+
+// A typedefInfo is an element on Package.typedefList: a typedef name
+// and the position where it was required.
+type typedefInfo struct {
+	typedef string
+	pos     token.Pos
 }
 
 // A File collects information about a single Go input file.