1diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
2index c4a44e3..4626e9b 100644
3--- a/doc/jemalloc.xml.in
4+++ b/doc/jemalloc.xml.in
5@@ -53,11 +53,23 @@
6     <para>This manual describes jemalloc @jemalloc_version@.  More information
7     can be found at the <ulink
8     url="http://www.canonware.com/jemalloc/">jemalloc website</ulink>.</para>
9+
10+    <para>The following configuration options are enabled in libc's built-in
11+    jemalloc: <option>--enable-fill</option>,
12+    <option>--enable-lazy-lock</option>, <option>--enable-munmap</option>,
13+    <option>--enable-stats</option>, <option>--enable-tcache</option>,
14+    <option>--enable-tls</option>, <option>--enable-utrace</option>, and
15+    <option>--enable-xmalloc</option>.  Additionally,
16+    <option>--enable-debug</option> is enabled in development versions of
17+    FreeBSD (controlled by the <constant>MK_MALLOC_PRODUCTION</constant> make
18+    variable).</para>
19+
20   </refsect1>
21   <refsynopsisdiv>
22     <title>SYNOPSIS</title>
23     <funcsynopsis>
24-      <funcsynopsisinfo>#include &lt;<filename class="headerfile">jemalloc/jemalloc.h</filename>&gt;</funcsynopsisinfo>
25+      <funcsynopsisinfo>#include &lt;<filename class="headerfile">stdlib.h</filename>&gt;
26+#include &lt;<filename class="headerfile">malloc_np.h</filename>&gt;</funcsynopsisinfo>
27       <refsect2>
28         <title>Standard API</title>
29         <funcprototype>
30@@ -2961,4 +2973,18 @@ malloc_conf = "lg_chunk:24";]]></programlisting></para>
31     <para>The <function>posix_memalign<parameter/></function> function conforms
32     to IEEE Std 1003.1-2001 (&ldquo;POSIX.1&rdquo;).</para>
33   </refsect1>
34+  <refsect1 id="history">
35+    <title>HISTORY</title>
36+    <para>The <function>malloc_usable_size<parameter/></function> and
37+    <function>posix_memalign<parameter/></function> functions first appeared in
38+    FreeBSD 7.0.</para>
39+
40+    <para>The <function>aligned_alloc<parameter/></function>,
41+    <function>malloc_stats_print<parameter/></function>, and
42+    <function>mallctl*<parameter/></function> functions first appeared in
43+    FreeBSD 10.0.</para>
44+
45+    <para>The <function>*allocx<parameter/></function> functions first appeared
46+    in FreeBSD 11.0.</para>
47+  </refsect1>
48 </refentry>
49diff --git a/include/jemalloc/internal/arena.h b/include/jemalloc/internal/arena.h
50index b1de2b6..da6b6d2 100644
51--- a/include/jemalloc/internal/arena.h
52+++ b/include/jemalloc/internal/arena.h
53@@ -718,8 +718,13 @@ arena_miscelm_get_mutable(arena_chunk_t *chunk, size_t pageind)
54 JEMALLOC_ALWAYS_INLINE const arena_chunk_map_misc_t *
55 arena_miscelm_get_const(const arena_chunk_t *chunk, size_t pageind)
56 {
57+#if 1 /* Work around gcc bug. */
58+	arena_chunk_t *mchunk = (arena_chunk_t *)chunk;
59 
60+	return (arena_miscelm_get_mutable(mchunk, pageind));
61+#else
62 	return (arena_miscelm_get_mutable((arena_chunk_t *)chunk, pageind));
63+#endif
64 }
65 
66 JEMALLOC_ALWAYS_INLINE size_t
67@@ -778,8 +783,13 @@ arena_mapbitsp_get_mutable(arena_chunk_t *chunk, size_t pageind)
68 JEMALLOC_ALWAYS_INLINE const size_t *
69 arena_mapbitsp_get_const(const arena_chunk_t *chunk, size_t pageind)
70 {
71+#if 1 /* Work around gcc bug. */
72+	arena_chunk_t *mchunk = (arena_chunk_t *)chunk;
73 
74+	return (arena_mapbitsp_get_mutable(mchunk, pageind));
75+#else
76 	return (arena_mapbitsp_get_mutable((arena_chunk_t *)chunk, pageind));
77+#endif
78 }
79 
80 JEMALLOC_ALWAYS_INLINE size_t
81diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
82index 8f82edd..78e2df2 100644
83--- a/include/jemalloc/internal/jemalloc_internal.h.in
84+++ b/include/jemalloc/internal/jemalloc_internal.h.in
85@@ -8,6 +8,9 @@
86 #include <sys/ktrace.h>
87 #endif
88 
89+#include "un-namespace.h"
90+#include "libc_private.h"
91+
92 #define	JEMALLOC_NO_DEMANGLE
93 #ifdef JEMALLOC_JET
94 #  define JEMALLOC_N(n) jet_##n
95@@ -42,13 +45,7 @@ static const bool config_fill =
96     false
97 #endif
98     ;
99-static const bool config_lazy_lock =
100-#ifdef JEMALLOC_LAZY_LOCK
101-    true
102-#else
103-    false
104-#endif
105-    ;
106+static const bool config_lazy_lock = true;
107 static const char * const config_malloc_conf = JEMALLOC_CONFIG_MALLOC_CONF;
108 static const bool config_prof =
109 #ifdef JEMALLOC_PROF
110diff --git a/include/jemalloc/internal/jemalloc_internal_decls.h b/include/jemalloc/internal/jemalloc_internal_decls.h
111index 2b8ca5d..42d97f2 100644
112--- a/include/jemalloc/internal/jemalloc_internal_decls.h
113+++ b/include/jemalloc/internal/jemalloc_internal_decls.h
114@@ -1,6 +1,9 @@
115 #ifndef JEMALLOC_INTERNAL_DECLS_H
116 #define	JEMALLOC_INTERNAL_DECLS_H
117 
118+#include "libc_private.h"
119+#include "namespace.h"
120+
121 #include <math.h>
122 #ifdef _WIN32
123 #  include <windows.h>
124diff --git a/include/jemalloc/internal/mutex.h b/include/jemalloc/internal/mutex.h
125index 5221799..60ab041 100644
126--- a/include/jemalloc/internal/mutex.h
127+++ b/include/jemalloc/internal/mutex.h
128@@ -52,9 +52,6 @@ struct malloc_mutex_s {
129 
130 #ifdef JEMALLOC_LAZY_LOCK
131 extern bool isthreaded;
132-#else
133-#  undef isthreaded /* Undo private_namespace.h definition. */
134-#  define isthreaded true
135 #endif
136 
137 bool	malloc_mutex_init(malloc_mutex_t *mutex, const char *name,
138@@ -62,6 +59,7 @@ bool	malloc_mutex_init(malloc_mutex_t *mutex, const char *name,
139 void	malloc_mutex_prefork(tsdn_t *tsdn, malloc_mutex_t *mutex);
140 void	malloc_mutex_postfork_parent(tsdn_t *tsdn, malloc_mutex_t *mutex);
141 void	malloc_mutex_postfork_child(tsdn_t *tsdn, malloc_mutex_t *mutex);
142+bool	malloc_mutex_first_thread(void);
143 bool	malloc_mutex_boot(void);
144 
145 #endif /* JEMALLOC_H_EXTERNS */
146diff --git a/include/jemalloc/internal/private_symbols.txt b/include/jemalloc/internal/private_symbols.txt
147index f2b6a55..69369c9 100644
148--- a/include/jemalloc/internal/private_symbols.txt
149+++ b/include/jemalloc/internal/private_symbols.txt
150@@ -311,7 +311,6 @@ iralloct_realign
151 isalloc
152 isdalloct
153 isqalloc
154-isthreaded
155 ivsalloc
156 ixalloc
157 jemalloc_postfork_child
158diff --git a/include/jemalloc/jemalloc_FreeBSD.h b/include/jemalloc/jemalloc_FreeBSD.h
159new file mode 100644
160index 0000000..c58a8f3
161--- /dev/null
162+++ b/include/jemalloc/jemalloc_FreeBSD.h
163@@ -0,0 +1,162 @@
164+/*
165+ * Override settings that were generated in jemalloc_defs.h as necessary.
166+ */
167+
168+#undef JEMALLOC_OVERRIDE_VALLOC
169+
170+#ifndef MALLOC_PRODUCTION
171+#define	JEMALLOC_DEBUG
172+#endif
173+
174+#undef JEMALLOC_DSS
175+
176+/*
177+ * The following are architecture-dependent, so conditionally define them for
178+ * each supported architecture.
179+ */
180+#undef JEMALLOC_TLS_MODEL
181+#undef STATIC_PAGE_SHIFT
182+#undef LG_SIZEOF_PTR
183+#undef LG_SIZEOF_INT
184+#undef LG_SIZEOF_LONG
185+#undef LG_SIZEOF_INTMAX_T
186+
187+#ifdef __i386__
188+#  define LG_SIZEOF_PTR		2
189+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
190+#endif
191+#ifdef __ia64__
192+#  define LG_SIZEOF_PTR		3
193+#endif
194+#ifdef __sparc64__
195+#  define LG_SIZEOF_PTR		3
196+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
197+#endif
198+#ifdef __amd64__
199+#  define LG_SIZEOF_PTR		3
200+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
201+#endif
202+#ifdef __arm__
203+#  define LG_SIZEOF_PTR		2
204+#endif
205+#ifdef __aarch64__
206+#  define LG_SIZEOF_PTR		3
207+#endif
208+#ifdef __mips__
209+#ifdef __mips_n64
210+#  define LG_SIZEOF_PTR		3
211+#else
212+#  define LG_SIZEOF_PTR		2
213+#endif
214+#endif
215+#ifdef __powerpc64__
216+#  define LG_SIZEOF_PTR		3
217+#elif defined(__powerpc__)
218+#  define LG_SIZEOF_PTR		2
219+#endif
220+#ifdef __riscv__
221+#  define LG_SIZEOF_PTR		3
222+#endif
223+
224+#ifndef JEMALLOC_TLS_MODEL
225+#  define JEMALLOC_TLS_MODEL	/* Default. */
226+#endif
227+
228+#define	STATIC_PAGE_SHIFT	PAGE_SHIFT
229+#define	LG_SIZEOF_INT		2
230+#define	LG_SIZEOF_LONG		LG_SIZEOF_PTR
231+#define	LG_SIZEOF_INTMAX_T	3
232+
233+#undef CPU_SPINWAIT
234+#include <machine/cpu.h>
235+#include <machine/cpufunc.h>
236+#define	CPU_SPINWAIT		cpu_spinwait()
237+
238+/* Disable lazy-lock machinery, mangle isthreaded, and adjust its type. */
239+#undef JEMALLOC_LAZY_LOCK
240+extern int __isthreaded;
241+#define	isthreaded		((bool)__isthreaded)
242+
243+/* Mangle. */
244+#undef je_malloc
245+#undef je_calloc
246+#undef je_posix_memalign
247+#undef je_aligned_alloc
248+#undef je_realloc
249+#undef je_free
250+#undef je_malloc_usable_size
251+#undef je_mallocx
252+#undef je_rallocx
253+#undef je_xallocx
254+#undef je_sallocx
255+#undef je_dallocx
256+#undef je_sdallocx
257+#undef je_nallocx
258+#undef je_mallctl
259+#undef je_mallctlnametomib
260+#undef je_mallctlbymib
261+#undef je_malloc_stats_print
262+#undef je_allocm
263+#undef je_rallocm
264+#undef je_sallocm
265+#undef je_dallocm
266+#undef je_nallocm
267+#define	je_malloc		__malloc
268+#define	je_calloc		__calloc
269+#define	je_posix_memalign	__posix_memalign
270+#define	je_aligned_alloc	__aligned_alloc
271+#define	je_realloc		__realloc
272+#define	je_free			__free
273+#define	je_malloc_usable_size	__malloc_usable_size
274+#define	je_mallocx		__mallocx
275+#define	je_rallocx		__rallocx
276+#define	je_xallocx		__xallocx
277+#define	je_sallocx		__sallocx
278+#define	je_dallocx		__dallocx
279+#define	je_sdallocx		__sdallocx
280+#define	je_nallocx		__nallocx
281+#define	je_mallctl		__mallctl
282+#define	je_mallctlnametomib	__mallctlnametomib
283+#define	je_mallctlbymib		__mallctlbymib
284+#define	je_malloc_stats_print	__malloc_stats_print
285+#define	je_allocm		__allocm
286+#define	je_rallocm		__rallocm
287+#define	je_sallocm		__sallocm
288+#define	je_dallocm		__dallocm
289+#define	je_nallocm		__nallocm
290+#define	open			_open
291+#define	read			_read
292+#define	write			_write
293+#define	close			_close
294+#define	pthread_mutex_lock	_pthread_mutex_lock
295+#define	pthread_mutex_unlock	_pthread_mutex_unlock
296+
297+#ifdef JEMALLOC_C_
298+/*
299+ * Define 'weak' symbols so that an application can have its own versions
300+ * of malloc, calloc, realloc, free, et al.
301+ */
302+__weak_reference(__malloc, malloc);
303+__weak_reference(__calloc, calloc);
304+__weak_reference(__posix_memalign, posix_memalign);
305+__weak_reference(__aligned_alloc, aligned_alloc);
306+__weak_reference(__realloc, realloc);
307+__weak_reference(__free, free);
308+__weak_reference(__malloc_usable_size, malloc_usable_size);
309+__weak_reference(__mallocx, mallocx);
310+__weak_reference(__rallocx, rallocx);
311+__weak_reference(__xallocx, xallocx);
312+__weak_reference(__sallocx, sallocx);
313+__weak_reference(__dallocx, dallocx);
314+__weak_reference(__sdallocx, sdallocx);
315+__weak_reference(__nallocx, nallocx);
316+__weak_reference(__mallctl, mallctl);
317+__weak_reference(__mallctlnametomib, mallctlnametomib);
318+__weak_reference(__mallctlbymib, mallctlbymib);
319+__weak_reference(__malloc_stats_print, malloc_stats_print);
320+__weak_reference(__allocm, allocm);
321+__weak_reference(__rallocm, rallocm);
322+__weak_reference(__sallocm, sallocm);
323+__weak_reference(__dallocm, dallocm);
324+__weak_reference(__nallocm, nallocm);
325+#endif
326diff --git a/include/jemalloc/jemalloc_rename.sh b/include/jemalloc/jemalloc_rename.sh
327index f943891..47d032c 100755
328--- a/include/jemalloc/jemalloc_rename.sh
329+++ b/include/jemalloc/jemalloc_rename.sh
330@@ -19,4 +19,6 @@ done
331 
332 cat <<EOF
333 #endif
334+
335+#include "jemalloc_FreeBSD.h"
336 EOF
337diff --git a/src/jemalloc.c b/src/jemalloc.c
338index 5d1f493..46dd1d1 100644
339--- a/src/jemalloc.c
340+++ b/src/jemalloc.c
341@@ -4,6 +4,10 @@
342 /******************************************************************************/
343 /* Data. */
344 
345+/* Work around <http://llvm.org/bugs/show_bug.cgi?id=12623>: */
346+const char	*__malloc_options_1_0 = NULL;
347+__sym_compat(_malloc_options, __malloc_options_1_0, FBSD_1.0);
348+
349 /* Runtime configuration options. */
350 const char	*je_malloc_conf JEMALLOC_ATTR(weak);
351 bool	opt_abort =
352@@ -2673,6 +2677,107 @@ je_malloc_usable_size(JEMALLOC_USABLE_SIZE_CONST void *ptr)
353  */
354 /******************************************************************************/
355 /*
356+ * Begin compatibility functions.
357+ */
358+
359+#define	ALLOCM_LG_ALIGN(la)	(la)
360+#define	ALLOCM_ALIGN(a)		(ffsl(a)-1)
361+#define	ALLOCM_ZERO		((int)0x40)
362+#define	ALLOCM_NO_MOVE		((int)0x80)
363+
364+#define	ALLOCM_SUCCESS		0
365+#define	ALLOCM_ERR_OOM		1
366+#define	ALLOCM_ERR_NOT_MOVED	2
367+
368+int
369+je_allocm(void **ptr, size_t *rsize, size_t size, int flags)
370+{
371+	void *p;
372+
373+	assert(ptr != NULL);
374+
375+	p = je_mallocx(size, flags);
376+	if (p == NULL)
377+		return (ALLOCM_ERR_OOM);
378+	if (rsize != NULL)
379+		*rsize = isalloc(tsdn_fetch(), p, config_prof);
380+	*ptr = p;
381+	return (ALLOCM_SUCCESS);
382+}
383+
384+int
385+je_rallocm(void **ptr, size_t *rsize, size_t size, size_t extra, int flags)
386+{
387+	int ret;
388+	bool no_move = flags & ALLOCM_NO_MOVE;
389+
390+	assert(ptr != NULL);
391+	assert(*ptr != NULL);
392+	assert(size != 0);
393+	assert(SIZE_T_MAX - size >= extra);
394+
395+	if (no_move) {
396+		size_t usize = je_xallocx(*ptr, size, extra, flags);
397+		ret = (usize >= size) ? ALLOCM_SUCCESS : ALLOCM_ERR_NOT_MOVED;
398+		if (rsize != NULL)
399+			*rsize = usize;
400+	} else {
401+		void *p = je_rallocx(*ptr, size+extra, flags);
402+		if (p != NULL) {
403+			*ptr = p;
404+			ret = ALLOCM_SUCCESS;
405+		} else
406+			ret = ALLOCM_ERR_OOM;
407+		if (rsize != NULL)
408+			*rsize = isalloc(tsdn_fetch(), *ptr, config_prof);
409+	}
410+	return (ret);
411+}
412+
413+int
414+je_sallocm(const void *ptr, size_t *rsize, int flags)
415+{
416+
417+	assert(rsize != NULL);
418+	*rsize = je_sallocx(ptr, flags);
419+	return (ALLOCM_SUCCESS);
420+}
421+
422+int
423+je_dallocm(void *ptr, int flags)
424+{
425+
426+	je_dallocx(ptr, flags);
427+	return (ALLOCM_SUCCESS);
428+}
429+
430+int
431+je_nallocm(size_t *rsize, size_t size, int flags)
432+{
433+	size_t usize;
434+
435+	usize = je_nallocx(size, flags);
436+	if (usize == 0)
437+		return (ALLOCM_ERR_OOM);
438+	if (rsize != NULL)
439+		*rsize = usize;
440+	return (ALLOCM_SUCCESS);
441+}
442+
443+#undef ALLOCM_LG_ALIGN
444+#undef ALLOCM_ALIGN
445+#undef ALLOCM_ZERO
446+#undef ALLOCM_NO_MOVE
447+
448+#undef ALLOCM_SUCCESS
449+#undef ALLOCM_ERR_OOM
450+#undef ALLOCM_ERR_NOT_MOVED
451+
452+/*
453+ * End compatibility functions.
454+ */
455+/******************************************************************************/
456+/*
457  * The following functions are used by threading libraries for protection of
458  * malloc during fork().
459  */
460@@ -2814,4 +2919,11 @@ jemalloc_postfork_child(void)
461 	ctl_postfork_child(tsd_tsdn(tsd));
462 }
463 
464+void
465+_malloc_first_thread(void)
466+{
467+
468+	(void)malloc_mutex_first_thread();
469+}
470+
471 /******************************************************************************/
472diff --git a/src/mutex.c b/src/mutex.c
473index a1fac34..a24e420 100644
474--- a/src/mutex.c
475+++ b/src/mutex.c
476@@ -66,6 +66,17 @@ pthread_create(pthread_t *__restrict thread,
477 #ifdef JEMALLOC_MUTEX_INIT_CB
478 JEMALLOC_EXPORT int	_pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
479     void *(calloc_cb)(size_t, size_t));
480+
481+#pragma weak _pthread_mutex_init_calloc_cb
482+int
483+_pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
484+    void *(calloc_cb)(size_t, size_t))
485+{
486+
487+	return (((int (*)(pthread_mutex_t *, void *(*)(size_t, size_t)))
488+	    __libc_interposing[INTERPOS__pthread_mutex_init_calloc_cb])(mutex,
489+	    calloc_cb));
490+}
491 #endif
492 
493 bool
494@@ -140,7 +151,7 @@ malloc_mutex_postfork_child(tsdn_t *tsdn, malloc_mutex_t *mutex)
495 }
496 
497 bool
498-malloc_mutex_boot(void)
499+malloc_mutex_first_thread(void)
500 {
501 
502 #ifdef JEMALLOC_MUTEX_INIT_CB
503@@ -154,3 +165,14 @@ malloc_mutex_boot(void)
504 #endif
505 	return (false);
506 }
507+
508+bool
509+malloc_mutex_boot(void)
510+{
511+
512+#ifndef JEMALLOC_MUTEX_INIT_CB
513+	return (malloc_mutex_first_thread());
514+#else
515+	return (false);
516+#endif
517+}
518diff --git a/src/util.c b/src/util.c
519index a1c4a2a..04f9153 100644
520--- a/src/util.c
521+++ b/src/util.c
522@@ -67,6 +67,22 @@ wrtmessage(void *cbopaque, const char *s)
523 
524 JEMALLOC_EXPORT void	(*je_malloc_message)(void *, const char *s);
525 
526+JEMALLOC_ATTR(visibility("hidden"))
527+void
528+wrtmessage_1_0(const char *s1, const char *s2, const char *s3,
529+    const char *s4)
530+{
531+
532+	wrtmessage(NULL, s1);
533+	wrtmessage(NULL, s2);
534+	wrtmessage(NULL, s3);
535+	wrtmessage(NULL, s4);
536+}
537+
538+void	(*__malloc_message_1_0)(const char *s1, const char *s2, const char *s3,
539+    const char *s4) = wrtmessage_1_0;
540+__sym_compat(_malloc_message, __malloc_message_1_0, FBSD_1.0);
541+
542 /*
543  * Wrapper around malloc_message() that avoids the need for
544  * je_malloc_message(...) throughout the code.
545