jemalloc cpp new/delete bindings

Adds cpp bindings for jemalloc, along with necessary autoconf settings.
This is mostly to add sized deallocation support, which can't be added
from C directly.  Sized deallocation is ~10% microbench improvement.

* Import ax_cxx_compile_stdcxx.m4 from the autoconf repo, seems like the
  easiest way to get c++14 detection.
* Adds various other changes, like CXXFLAGS, to configure.ac.
* Adds new rules to Makefile.in for src/jemalloc-cpp.cpp, and a basic
  unittest.
* Both new and delete are overridden, to ensure jemalloc is used for
  both.
* TODO future enhancement of avoiding extra PLT thunks for new and
  delete - sdallocx and malloc are publicly exported jemalloc symbols,
  using an alias would link them directly.  Unfortunately, was having
  trouble getting it to play nice with jemalloc's namespace support.

Testing:
Tested gcc 4.8, gcc 5, gcc 5.2, clang 4.0.  Only gcc >= 5 has sized
deallocation support, verified that the rest build correctly.

Tested mac osx and Centos.

Tested --with-jemalloc-prefix and --without-export.

This resolves #202.

3 files changed, 17 insertions, 6 deletions

diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index 85b34012..ba5207d8 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -1,6 +1,10 @@
 #ifndef JEMALLOC_INTERNAL_H
 #define	JEMALLOC_INTERNAL_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "jemalloc_internal_defs.h"
 #include "jemalloc/internal/jemalloc_internal_decls.h"
 
@@ -135,7 +139,7 @@ static const bool config_cache_oblivious =
 #endif
     ;
 
-#ifdef JEMALLOC_C11ATOMICS
+#if defined(JEMALLOC_C11ATOMICS) && !defined(__cplusplus)
 #include <stdatomic.h>
 #endif
 
@@ -888,7 +892,7 @@ arena_get(tsdn_t *tsdn, unsigned ind, bool init_if_missing)
 
 	ret = arenas[ind];
 	if (unlikely(ret == NULL)) {
-		ret = atomic_read_p((void *)&arenas[ind]);
+		ret = (arena_t *)atomic_read_p((void **)&arenas[ind]);
 		if (init_if_missing && unlikely(ret == NULL))
 			ret = arena_init(tsdn, ind);
 	}
@@ -1194,4 +1198,9 @@ ixalloc(tsdn_t *tsdn, extent_t *extent, void *ptr, size_t oldsize, size_t size,
 
 #undef JEMALLOC_H_INLINES
 /******************************************************************************/
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* JEMALLOC_INTERNAL_H */
diff --git a/include/jemalloc/internal/jemalloc_internal_macros.h b/include/jemalloc/internal/jemalloc_internal_macros.h
index a08ba772..57492049 100644
--- a/include/jemalloc/internal/jemalloc_internal_macros.h
+++ b/include/jemalloc/internal/jemalloc_internal_macros.h
@@ -52,6 +52,6 @@
 #  define	__DECONST(type, var)	((type)(uintptr_t)(const void *)(var))
 #endif
 
-#ifndef JEMALLOC_HAS_RESTRICT
+#if !defined(JEMALLOC_HAS_RESTRICT) || defined(__cplusplus)
 #  define restrict
 #endif
diff --git a/include/jemalloc/internal/rtree.h b/include/jemalloc/internal/rtree.h
index 9c6cc22f..b2a2800e 100644
--- a/include/jemalloc/internal/rtree.h
+++ b/include/jemalloc/internal/rtree.h
@@ -260,7 +260,7 @@ rtree_child_tryread(rtree_elm_t *elm, bool dependent)
 	/* Double-checked read (first read may be stale). */
 	child = elm->child;
 	if (!dependent && !rtree_node_valid(child))
-		child = atomic_read_p(&elm->pun);
+		child = (rtree_elm_t *)atomic_read_p(&elm->pun);
 	assert(!dependent || child != NULL);
 	return (child);
 }
@@ -320,8 +320,10 @@ rtree_subtree_tryread(rtree_t *rtree, unsigned level, bool dependent)
 
 	/* Double-checked read (first read may be stale). */
 	subtree = rtree->levels[level].subtree;
-	if (!dependent && unlikely(!rtree_node_valid(subtree)))
-		subtree = atomic_read_p(&rtree->levels[level].subtree_pun);
+	if (!dependent && unlikely(!rtree_node_valid(subtree))) {
+		subtree = (rtree_elm_t *)atomic_read_p(
+		    &rtree->levels[level].subtree_pun);
+	}
 	assert(!dependent || subtree != NULL);
 	return (subtree);
 }