Correct prediction hint for nullptr in do_free_with_size()

TCMalloc Team · copybara-github · commit 9b4d2fd2ea0b · 2025-10-08T17:08:22.000-07:00
Change `ABSL_PREDICT_TRUE` to `ABSL_PREDICT_FALSE` for the `ptr == nullptr` check within the non-normal memory path of do_free_with_size(). Deleting a nullptr is a valid but expectedly rare operation in this context.

PiperOrigin-RevId: 816920767
Change-Id: I7037b6190a2c1a7dbccc762111fa923e5da22364
diff --git a/tcmalloc/tcmalloc.cc b/tcmalloc/tcmalloc.cc
@@ -824,7 +824,7 @@ inline ABSL_ATTRIBUTE_ALWAYS_INLINE void do_free_with_size(void* ptr,
   // The optimized path doesn't work with non-normal objects (sampled, cold),
   // whose deletions trigger more operations and require to visit metadata.
   if (ABSL_PREDICT_FALSE(!IsNormalMemory(ptr))) {
-    if (ABSL_PREDICT_TRUE(ptr == nullptr)) {
+    if (ABSL_PREDICT_FALSE(ptr == nullptr)) {
       return;
     }
     if (ABSL_PREDICT_TRUE(IsSelSanMemory(ptr))) {

Original file line number	Diff line number	Diff line change
`@@ -824,7 +824,7 @@ inline ABSL_ATTRIBUTE_ALWAYS_INLINE void do_free_with_size(void* ptr,`
`824`	`824`	`// The optimized path doesn't work with non-normal objects (sampled, cold),`
`825`	`825`	`// whose deletions trigger more operations and require to visit metadata.`
`826`	`826`	`if (ABSL_PREDICT_FALSE(!IsNormalMemory(ptr))) {`
`827`		`- if (ABSL_PREDICT_TRUE(ptr == nullptr)) {`
	`827`	`+ if (ABSL_PREDICT_FALSE(ptr == nullptr)) {`
`828`	`828`	`return;`
`829`	`829`	`}`
`830`	`830`	`if (ABSL_PREDICT_TRUE(IsSelSanMemory(ptr))) {`