Make fbstring libgcc-safe

[folly.git] / folly / SmallLocks.h

diff --git a/folly/SmallLocks.h b/folly/SmallLocks.h
index cefe2f3a0fe4b5cad386cfe3a2032c2a48664e46..b8f081a668b5e2401ea8f483c5f67901bdede4f9 100644 (file)
--- a/folly/SmallLocks.h
+++ b/folly/SmallLocks.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,8 +44,9 @@
 #include <mutex>
 
 #include <glog/logging.h>
+#include "folly/Portability.h"
 
-#ifndef __x86_64__
+#if !FOLLY_X64
 # error "SmallLocks.h is currently x64-only."
 #endif
 
@@ -78,7 +79,7 @@ namespace detail {
          * linux this varies by kernel version from 1ms to 10ms).
          */
         struct timespec ts = { 0, 500000 };
-        nanosleep(&ts, NULL);
+        nanosleep(&ts, nullptr);
       }
     }
   };
@@ -109,12 +110,13 @@ struct MicroSpinLock {
    */
   bool cas(uint8_t compare, uint8_t newVal) {
     bool out;
-    asm volatile("lock; cmpxchgb %2, (%3);"
-                 "setz %0;"
-                 : "=r" (out)
+    bool memVal; // only set if the cmpxchg fails
+    asm volatile("lock; cmpxchgb %[newVal], (%[lockPtr]);"
+                 "setz %[output];"
+                 : [output] "=r" (out), "=a" (memVal)
                  : "a" (compare), // cmpxchgb constrains this to be in %al
-                   "q" (newVal),  // Needs to be byte-accessible
-                   "r" (&lock_)
+                   [newVal] "q" (newVal),  // Needs to be byte-accessible
+                   [lockPtr] "r" (&lock_)
                  : "memory", "flags");
     return out;
   }
@@ -309,7 +311,6 @@ struct SpinLockArray {
   // Check if T can theoretically cross a cache line.
   // NOTE: It should be alignof(std::max_align_t), but max_align_t
   // isn't supported by gcc 4.6.2.
-  struct MaxAlign { char c; } __attribute__((aligned));
   static_assert(alignof(MaxAlign) > 0 &&
                 FOLLY_CACHE_LINE_SIZE % alignof(MaxAlign) == 0 &&
                 sizeof(T) <= alignof(MaxAlign),