From 08270c3e18673f7f1319dce9d27d84c9a4c8eb49 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Thu, 9 Nov 2017 23:58:42 -0500
Subject: [PATCH] cmd/cover: do not report coverage for assembly functions

cover -func mode was reporting a coverage for function
declarations without bodies - assembly functions.
Since we are not annotating their code, we have no data
for those functions and should not report them at all.

Fixes #6880.

Change-Id: I4b8cd90805accf61f54e3ee167f54f4dc10c7c59
Reviewed-on: https://go-review.googlesource.com/77152
Reviewed-by: Ian Lance Taylor <iant@golang.org>
---
 src/cmd/cover/func.go                      |  4 ++++
 src/cmd/go/go_test.go                      | 13 +++++++++++++
 src/cmd/go/testdata/src/coverasm/p.go      |  7 +++++++
 src/cmd/go/testdata/src/coverasm/p.s       |  2 ++
 src/cmd/go/testdata/src/coverasm/p_test.go |  7 +++++++
 5 files changed, 33 insertions(+)
 create mode 100644 src/cmd/go/testdata/src/coverasm/p.go
 create mode 100644 src/cmd/go/testdata/src/coverasm/p.s
 create mode 100644 src/cmd/go/testdata/src/coverasm/p_test.go

diff --git a/src/cmd/cover/func.go b/src/cmd/cover/func.go
index 05c7c12c99..1673fbf315 100644
--- a/src/cmd/cover/func.go
+++ b/src/cmd/cover/func.go
@@ -113,6 +113,10 @@ type FuncVisitor struct {
 func (v *FuncVisitor) Visit(node ast.Node) ast.Visitor {
 	switch n := node.(type) {
 	case *ast.FuncDecl:
+		if n.Body == nil {
+			// Do not count declarations of assembly functions.
+			break
+		}
 		start := v.fset.Position(n.Pos())
 		end := v.fset.Position(n.End())
 		fe := &FuncExtent{
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index d2933bc3cb..9dd5f8347c 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -2457,6 +2457,19 @@ func TestCoverageErrorLine(t *testing.T) {
 	}
 }
 
+func TestCoverageFunc(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.makeTempdir()
+	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
+
+	tg.run("test", "-coverprofile="+filepath.Join(tg.tempdir, "cover.out"), "coverasm")
+	tg.run("tool", "cover", "-func="+filepath.Join(tg.tempdir, "cover.out"))
+	tg.grepStdout(`\tg\t*100.0%`, "did not find g 100% covered")
+	tg.grepStdoutNot(`\tf\t*[0-9]`, "reported coverage for assembly function f")
+}
+
 func TestPluginNonMain(t *testing.T) {
 	wd, err := os.Getwd()
 	if err != nil {
diff --git a/src/cmd/go/testdata/src/coverasm/p.go b/src/cmd/go/testdata/src/coverasm/p.go
new file mode 100644
index 0000000000..ab0c300d72
--- /dev/null
+++ b/src/cmd/go/testdata/src/coverasm/p.go
@@ -0,0 +1,7 @@
+package p
+
+func f()
+
+func g() {
+	println("g")
+}
diff --git a/src/cmd/go/testdata/src/coverasm/p.s b/src/cmd/go/testdata/src/coverasm/p.s
new file mode 100644
index 0000000000..5e728f9946
--- /dev/null
+++ b/src/cmd/go/testdata/src/coverasm/p.s
@@ -0,0 +1,2 @@
+// empty asm file,
+// so go test doesn't complain about declaration of f in p.go.
diff --git a/src/cmd/go/testdata/src/coverasm/p_test.go b/src/cmd/go/testdata/src/coverasm/p_test.go
new file mode 100644
index 0000000000..3cb3bd5664
--- /dev/null
+++ b/src/cmd/go/testdata/src/coverasm/p_test.go
@@ -0,0 +1,7 @@
+package p
+
+import "testing"
+
+func Test(t *testing.T) {
+	g()
+}