cmd/cgo/internal/test: skip TestMultipleAssign when using UCRT on Windows

The Universal C Runtime (UCRT) default behavior is to crash the program
when strtol is called with an invalid base (that is, not 0 or 2..36).
This an invalid base (that is, not 0 or 2..36). This changes the test to
skip when running on Windows and linking with UCRT.

When using external linking mode this test passes if using the Mingw-w64
toolchain, even when linking with UCRT. That's because the Mingw-w64
linker adds a _set_invalid_parameter_handler call at startup that
overrides the default UCRT behavior. However, other toolchains, like
MSVC and LLVM, doesn't override the default behavior.

Overriding the default behavior is out of the scope for this test, so
the test is skipped instead.

Fixes #62887

Change-Id: I60f140faf0eda80a2de4e10876be25e0dbe442d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/705455
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

src/cmd/cgo/internal/test/test.go

@@ -1096,6 +1096,12 @@ func testErrno(t *testing.T) {
 }
 
 func testMultipleAssign(t *testing.T) {
+	if runtime.GOOS == "windows" && usesUCRT(t) {
+		// UCRT's strtol throws an unrecoverable crash when
+		// using an invalid base (that is, not 0 or 2..36).
+		// See go.dev/issue/62887.
+		t.Skip("skipping test on Windows when linking with UCRT")
+	}
 	p := C.CString("234")
 	n, m := C.strtol(p, nil, 345), C.strtol(p, nil, 10)
 	defer C.free(unsafe.Pointer(p))

src/cmd/cgo/internal/test/test_unix.go

@@ -6,6 +6,13 @@
 
 package cgotest
 
-import "syscall"
+import (
+	"syscall"
+	"testing"
+)
 
 var syscall_dot_SIGCHLD = syscall.SIGCHLD
+
+func usesUCRT(t *testing.T) bool {
+	return false
+}

src/cmd/cgo/internal/test/test_windows.go

@@ -4,6 +4,20 @@
 
 package cgotest
 
-import "syscall"
+import (
+	"internal/syscall/windows"
+	"syscall"
+	"testing"
+)
 
 var syscall_dot_SIGCHLD syscall.Signal
+
+// usesUCRT reports whether the test is using the Windows UCRT (Universal C Runtime).
+func usesUCRT(t *testing.T) bool {
+	name, err := syscall.UTF16PtrFromString("ucrtbase.dll")
+	if err != nil {
+		t.Fatal(err)
+	}
+	h, err := windows.GetModuleHandle(name)
+	return err == nil && h != 0
+}