[dtrace] Make sure when instrumenting release to be sure that arg0 is not nullptr. I had this check with swift_retain, but I forgot to use it in swift_release.

gottesmm · gottesmm · commit 25674b7adb49 · 2016-02-25T12:31:11.000-08:00
diff --git a/utils/runtime_statistics.d b/utils/runtime_statistics.d
@@ -33,7 +33,7 @@ pid$target:libswiftCore:swift_retain:entry / arg0 != 0 /
     @counts["swift_retain", "global"] = count();
 }
 
-pid$target:*:swift_release:entry
+pid$target:*:swift_release:entry / arg0 != 0 /
 {
     this->ptr = (HeapObject *)copyin(arg0, sizeof(HeapObject));
     this->metadata = (ClassMetadata *)copyin(this->ptr->M, sizeof(ClassMetadata));

Original file line number	Diff line number	Diff line change
`@@ -33,7 +33,7 @@ pid$target:libswiftCore:swift_retain:entry / arg0 != 0 /`
`33`	`33`	`@counts["swift_retain", "global"] = count();`
`34`	`34`	`}`
`35`	`35`
`36`		`-pid$target:*:swift_release:entry`
	`36`	`+pid$target:*:swift_release:entry / arg0 != 0 /`
`37`	`37`	`{`
`38`	`38`	`this->ptr = (HeapObject *)copyin(arg0, sizeof(HeapObject));`
`39`	`39`	`this->metadata = (ClassMetadata *)copyin(this->ptr->M, sizeof(ClassMetadata));`