Use system allocator when jemalloc is unavailable

This commit adds support for systems where the jemalloc library is not
available as a package, here's the quick summary:

  * On Linux - the jemalloc is usually available as a package, if
    configured --without-jemalloc, the shim would be used around
    malloc(), free(), realloc() and malloc_usable_size()

  * On macOS - the jemalloc is available from homebrew or macports, if
    configured --without-jemalloc, the shim would be used around
    malloc(), free(), realloc() and malloc_size()

  * On FreeBSD - the jemalloc is *the* system allocator, we just need
    to check for <malloc_np.h> header to get access to non-standard API

  * On NetBSD - the jemalloc is *the* system allocator, we just need to
    check for <jemalloc/jemalloc.h> header to get access to non-standard
    API

  * On a system hostile to users and developers (read OpenBSD) - the
    jemalloc API is emulated by using ((size_t *)ptr)[-1] field to hold
    the size information.  The OpenBSD developers care only for
    themselves, so why should we care about speed on OpenBSD?

lib/isc/Makefile.am

@@ -167,6 +167,7 @@ libisc_la_SOURCES =		\
 	httpd.c			\
 	interfaceiter.c		\
 	iterated_hash.c		\
+	jemalloc_shim.h		\
 	lex.c			\
 	lib.c			\
 	log.c			\

lib/isc/jemalloc_shim.h

@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#pragma once
+
+#if !defined(HAVE_JEMALLOC)
+
+#include <isc/util.h>
+
+const char *malloc_conf = NULL;
+
+#if defined(HAVE_MALLOC_SIZE) || defined(HAVE_MALLOC_USABLE_SIZE)
+
+#include <stdlib.h>
+
+static inline void *
+mallocx(size_t size, int flags) {
+	UNUSED(flags);
+	void *__ptr = malloc(size);
+	REQUIRE(__ptr != NULL);
+	return (__ptr);
+}
+
+static inline void
+sdallocx(void *ptr, size_t size, int flags) {
+	UNUSED(size);
+	UNUSED(flags);
+
+	free(ptr);
+}
+
+static inline void *
+rallocx(void *ptr, size_t size, int flags) {
+	UNUSED(flags);
+	REQUIRE(size != 0);
+
+	void *__ptr = realloc(ptr, size);
+	REQUIRE(__ptr != NULL);
+
+	return (__ptr);
+}
+
+#ifdef HAVE_MALLOC_SIZE
+
+#include <malloc/malloc.h>
+
+static inline size_t
+sallocx(void *ptr, int flags) {
+	UNUSED(flags);
+
+	return (malloc_size(ptr));
+}
+
+#elif HAVE_MALLOC_USABLE_SIZE
+
+#include <malloc.h>
+
+static inline size_t
+sallocx(void *ptr, int flags) {
+	UNUSED(flags);
+
+	return (malloc_usable_size(ptr));
+}
+
+#endif /* HAVE_MALLOC_SIZE */
+
+#else /* defined(HAVE_MALLOC_SIZE) || defined (HAVE_MALLOC_USABLE_SIZE) */
+
+#include <stdlib.h>
+
+static inline void *
+mallocx(size_t size, int flags) {
+	UNUSED(flags);
+
+	size_t *__ptr = malloc(size + sizeof(size_t));
+	REQUIRE(__ptr != NULL);
+	__ptr[0] = size;
+
+	return (&__ptr[1]);
+}
+
+static inline void
+sdallocx(void *ptr, size_t size, int flags) {
+	UNUSED(size);
+	UNUSED(flags);
+
+	free(&((size_t *)ptr)[-1]);
+}
+
+static inline size_t
+sallocx(void *ptr, int flags) {
+	UNUSED(flags);
+
+	return (((size_t *)ptr)[-1]);
+}
+
+static inline void *
+rallocx(void *ptr, size_t size, int flags) {
+	UNUSED(flags);
+
+	size_t *__ptr = realloc(&((size_t *)ptr)[-1], size);
+	REQUIRE(__ptr != NULL);
+	__ptr[0] = size;
+
+	return (&__ptr[1]);
+}
+
+#endif /* defined(HAVE_MALLOC_SIZE) || defined (HAVE_MALLOC_USABLE_SIZE) */
+
+#endif /* !defined(HAVE_JEMALLOC) */

lib/isc/mem.c

@@ -42,8 +42,19 @@
 #include <json_object.h>
 #endif /* HAVE_JSON_C */
 
+#if defined(HAVE_MALLOC_NP_H)
+#include <malloc_np.h>
+#elif defined(HAVE_JEMALLOC)
 #include <jemalloc/jemalloc.h>
 
+#if JEMALLOC_VERSION_MAJOR < 4
+#define sdallocx(ptr, size, flags) dallocx(ptr, flags)
+#endif /* JEMALLOC_VERSION_MAJOR < 4 */
+
+#else
+#include "jemalloc_shim.h"
+#endif
+
 #include "mem_p.h"
 
 #define MCTXLOCK(m)   LOCK(&m->lock)