Bug 1356701 - Export unprefixed malloc and duplication functions on OSX. r=njn
☠☠ backed out by 11755fd63168 ☠ ☠
authorMike Hommey <mh+mozilla@glandium.org>
Tue, 04 Jul 2017 15:01:50 +0900
changeset 367232 261d61f4eeecbcf143a816fbfd43476b511779de
parent 367231 09218c30275a5ee66eee1e990aac19bcba374451
child 367233 493a2e4824e076e27bb5f9877aaec932231966e9
push id32128
push userphilringnalda@gmail.com
push dateWed, 05 Jul 2017 03:30:48 +0000
treeherdermozilla-central@0893f6685e15 [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
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last release without
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nightly win32
nightly win64
Bug 1356701 - Export unprefixed malloc and duplication functions on OSX. r=njn Going through the system zone allocator for every call to realloc/free on OSX is costly, because the zone allocator needs to first verify that the allocations do belong to the allocator it invokes (which ends up calling jemalloc's malloc_usable_size), which is unnecessary when we expect the allocations to belong to jemalloc. So, we export the malloc/realloc/free/etc. symbols from libmozglue.dylib, such that libraries and programs linked against it calls directly into jemalloc instead of going through the system zone allocator, effectively shortcutting the allocator verification. The risk is that some things in Gecko try to realloc/free pointers it got from system libraries, if those were allocated with a system zone that is not jemalloc.
--- a/memory/build/mozmemory_wrap.c
+++ b/memory/build/mozmemory_wrap.c
@@ -63,17 +63,16 @@ mozmem_malloc_impl(_ZdaPvRKSt9nothrow_t)
 /* strndup and strdup may be defined as macros in string.h, which would
  * clash with the definitions below. */
 #undef strndup
 #undef strdup
-#ifndef XP_DARWIN
 strndup_impl(const char *src, size_t len)
   char* dst = (char*) malloc_impl(len + 1);
   if (dst) {
     strncpy(dst, src, len);
     dst[len] = '\0';
@@ -81,17 +80,16 @@ strndup_impl(const char *src, size_t len
 strdup_impl(const char *src)
   size_t len = strlen(src);
   return strndup_impl(src, len);
-#endif /* XP_DARWIN */
 #ifdef ANDROID
 #include <stdarg.h>
 #include <stdio.h>
 vasprintf_impl(char **str, const char *fmt, va_list ap)
--- a/memory/build/mozmemory_wrap.h
+++ b/memory/build/mozmemory_wrap.h
@@ -48,21 +48,20 @@
  *   specific functions are left unprefixed. All these functions are however
  *   aliased when exporting them, such that the resulting mozglue.dll exports
  *   them unprefixed (see $(topsrcdir)/mozglue/build/mozglue.def.in). The
  *   prefixed malloc implementation and duplication functions are not
  *   exported.
  * - On MacOSX, the system libc has a zone allocator, which allows us to
  *   hook custom malloc implementation functions without exporting them.
- *   The malloc implementation functions are all prefixed with "je_" and used
- *   this way from the custom zone allocator. They are not exported.
- *   Duplication functions are not included, since they will call the custom
- *   zone allocator anyways. Jemalloc-specific functions are also left
- *   unprefixed.
+ *   However, since we want things in Firefox to skip the system zone
+ *   allocator, the malloc implementation functions are all exported
+ *   unprefixed, as well as duplication functions.
+ *   Jemalloc-specific functions are also left unprefixed.
  * - On Android and Gonk, all functions are left unprefixed. Additionally,
  *   C++ allocation functions (operator new/delete) are also exported and
  *   unprefixed.
  * - On other systems (mostly Linux), all functions are left unprefixed.
  * Only Android and Gonk add C++ allocation functions.
@@ -129,17 +128,17 @@
 #  if defined(MOZ_JEMALLOC_IMPL) && defined(MOZ_REPLACE_MALLOC)
 #    define mozmem_malloc_impl(a)     je_ ## a
 #    define mozmem_jemalloc_impl(a)   je_ ## a
 #  else
-#    if (defined(XP_WIN) || defined(XP_DARWIN))
+#    if defined(XP_WIN)
 #      if defined(MOZ_REPLACE_MALLOC)
 #        define mozmem_malloc_impl(a)   a ## _impl
 #      else
 #        define mozmem_malloc_impl(a)   je_ ## a
 #      endif
 #    else
 #      if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_GONK)