From: Christopher Dykes <cdykes@fb.com>
Date: Thu, 26 Oct 2017 19:15:55 +0000 (-0700)
Subject: Just use a volatile static in Malloc.h
X-Git-Tag: v2017.10.30.00~11
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a15fcb1e76444f7d464b263ad37bf3b5fbfdf33e;p=folly.git

Just use a volatile static in Malloc.h

Summary: As suggested late in the initial diff (D5840883), just mark it volatile, as it works under all supported platforms.

Reviewed By: davidtgoldblatt, yfeldblum

Differential Revision: D6155241

fbshipit-source-id: 00c07a11dc7fc2e33c2d1f9a45fd28006eeff6f9
---

diff --git a/folly/memory/Malloc.h b/folly/memory/Malloc.h
index 2726c9d8..5bad7484 100644
--- a/folly/memory/Malloc.h
+++ b/folly/memory/Malloc.h
@@ -183,15 +183,12 @@ FOLLY_MALLOC_NOINLINE inline bool usingJEMalloc() noexcept {
 
     uint64_t origAllocated = *counter;
 
-    const void* ptr = malloc(1);
+    static const void* volatile ptr = malloc(1);
     if (!ptr) {
       // wtf, failing to allocate 1 byte
       return false;
     }
 
-    /* Avoid optimizing away the malloc.  */
-    asm volatile("" ::"m"(ptr) : "memory");
-
     return (origAllocated != *counter);
   }();