Improvement: span_id should not break strict aliasing.

hcoona · hcoona · commit cc4c09c4a8e6 · 2021-11-16T12:11:21.000+08:00
diff --git a/api/include/opentelemetry/trace/span_id.h b/api/include/opentelemetry/trace/span_id.h
@@ -61,7 +61,8 @@ class SpanId final
   bool IsValid() const noexcept
   {
     static_assert(kSize == 8, "update is needed if kSize is not 8");
-    return *reinterpret_cast<const uint64_t *>(&rep_) != 0ull;
+    static constexpr uint8_t kEmptyRep[kSize] = {0};
+    return memcmp(rep_, kEmptyRep, kSize) != 0;
   }
 
   // Copies the opaque SpanId data to dest.

Original file line number	Diff line number	Diff line change
`@@ -61,7 +61,8 @@ class SpanId final`
`61`	`61`	`bool IsValid() const noexcept`
`62`	`62`	`{`
`63`	`63`	`static_assert(kSize == 8, "update is needed if kSize is not 8");`
`64`		`- return reinterpret_cast<const uint64_t >(&rep_) != 0ull;`
	`64`	`+ static constexpr uint8_t kEmptyRep[kSize] = {0};`
	`65`	`+ return memcmp(rep_, kEmptyRep, kSize) != 0;`
`65`	`66`	`}`
`66`	`67`
`67`	`68`	`// Copies the opaque SpanId data to dest.`