Do not initialize the allocator on free(nullptr). (#74366)

free(nullptr) is guaranteed by ISO and POSIX to be a no-op, we should not pay for the overhead of maybeInit() in this case.

Additionally, Bionic calls free(nullptr) before the allocator settings are finalized.
Scudo should not run allocator initialization at that time. Doing so
causes various bad things to happen, like mapping primary regions with
the wrong PROT_MTE setting.

Author: eugenis

compiler-rt/lib/scudo/standalone/combined.h

@@ -522,6 +522,9 @@ class Allocator {
 
   NOINLINE void deallocate(void *Ptr, Chunk::Origin Origin, uptr DeleteSize = 0,
                            UNUSED uptr Alignment = MinAlignment) {
+    if (UNLIKELY(!Ptr))
+      return;
+
     // For a deallocation, we only ensure minimal initialization, meaning thread
     // local data will be left uninitialized for now (when using ELF TLS). The
     // fallback cache will be used instead. This is a workaround for a situation
@@ -530,9 +533,6 @@ class Allocator {
     // being destroyed properly. Any other heap operation will do a full init.
     initThreadMaybe(/*MinimalInit=*/true);
 
-    if (UNLIKELY(!Ptr))
-      return;
-
 #ifdef GWP_ASAN_HOOKS
     if (UNLIKELY(GuardedAlloc.pointerIsMine(Ptr))) {
       GuardedAlloc.deallocate(Ptr);