misc/cgo/testsigfwd: move to runtime/testprog/testprogcgo

This migrates testsigfwd, which uses some one-off build
infrastructure, to be part of the runtime's testprogcgo.

The test is largely unchanged. Because it's part of a larger binary,
this CL renames a few things and gates the constructor-time signal
handler registration on an environment variable. This CL also replaces
an errant fmt.Errorf with fmt.Fprintf.

For #37486, since it eliminates a non-go-test from dist.

Change-Id: I0efd146ea0a0a3f0b361431349a419af0f0ecc61
Reviewed-on: https://go-review.googlesource.com/c/go/+/443068
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/dist/test.go

@@ -831,9 +831,6 @@ func (t *tester) registerTests() {
 		if t.hasBash() && goos != "android" && !t.iOS() && gohostos != "windows" {
 			t.registerHostTest("cgo_errors", "../misc/cgo/errors", "misc/cgo/errors", ".")
 		}
-		if gohostos == "linux" && t.extLink() {
-			t.registerTest("testsigfwd", "../misc/cgo/testsigfwd", "go", "run", ".")
-		}
 	}
 
 	if goos != "android" && !t.iOS() {

src/runtime/crash_cgo_test.go

@@ -8,6 +8,7 @@ package runtime_test
 
 import (
 	"fmt"
+	"internal/goos"
 	"internal/testenv"
 	"os"
 	"os/exec"
@@ -753,3 +754,15 @@ func TestCgoTraceParserWithOneProc(t *testing.T) {
 		t.Fatalf("GOMAXPROCS=1, want %s, got %s\n", want, output)
 	}
 }
+
+func TestCgoSigfwd(t *testing.T) {
+	t.Parallel()
+	if goos.IsLinux == 0 {
+		t.Skipf("only supported on Linux")
+	}
+
+	got := runTestProg(t, "testprogcgo", "CgoSigfwd", "GO_TEST_CGOSIGFWD=1")
+	if want := "OK\n"; got != want {
+		t.Fatalf("expected %q, but got:\n%s", want, got)
+	}
+}

src/runtime/testdata/testprogcgo/sigfwd.go

@@ -2,9 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux
+
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+)
 
 /*
 #include <signal.h>
@@ -12,21 +17,25 @@ import "fmt"
 #include <stdio.h>
 #include <string.h>
 
-int *p;
+int *sigfwdP;
 static void sigsegv() {
-	*p = 1;
+	*sigfwdP = 1;
 	fprintf(stderr, "ERROR: C SIGSEGV not thrown on caught?.\n");
 	exit(2);
 }
 
 static void segvhandler(int signum) {
 	if (signum == SIGSEGV) {
-		fprintf(stdout, "ok\ttestsigfwd\n");
+		fprintf(stdout, "OK\n");
 		exit(0);  // success
 	}
 }
 
 static void __attribute__ ((constructor)) sigsetup(void) {
+	if (getenv("GO_TEST_CGOSIGFWD") == NULL) {
+		return;
+	}
+
 	struct sigaction act;
 
 	memset(&act, 0, sizeof act);
@@ -36,7 +45,11 @@ static void __attribute__ ((constructor)) sigsetup(void) {
 */
 import "C"
 
-var p *byte
+func init() {
+	register("CgoSigfwd", CgoSigfwd)
+}
+
+var nilPtr *byte
 
 func f() (ret bool) {
 	defer func() {
@@ -46,14 +59,19 @@ func f() (ret bool) {
 		}
 		ret = true
 	}()
-	*p = 1
+	*nilPtr = 1
 	return false
 }
 
-func main() {
+func CgoSigfwd() {
+	if os.Getenv("GO_TEST_CGOSIGFWD") == "" {
+		fmt.Fprintf(os.Stderr, "test must be run with GO_TEST_CGOSIGFWD set\n")
+		os.Exit(1)
+	}
+
 	// Test that the signal originating in Go is handled (and recovered) by Go.
 	if !f() {
-		fmt.Errorf("couldn't recover from SIGSEGV in Go.")
+		fmt.Fprintf(os.Stderr, "couldn't recover from SIGSEGV in Go.\n")
 		C.exit(2)
 	}