Test for availability of malloc hooks via autoconf

__*_hook() is glibc, but on at least one glibc platform (homebrew),
the __GLIBC__ define isn't set correctly and we miss being able to
use these hooks.

Do a feature test for it during configuration so that we enable it
anywhere the hooks are actually available.

configure.ac

@@ -1340,6 +1340,37 @@ if test "x${enable_zone_allocator}" = "x1" ; then
   AC_DEFINE_UNQUOTED(JEMALLOC_ZONE_VERSION, [$JEMALLOC_ZONE_VERSION])
 fi
 
+dnl ============================================================================
+dnl Check for glibc malloc hooks
+
+JE_COMPILABLE([glibc malloc hook], [
+#include <stddef.h>
+
+extern void (* __free_hook)(void *ptr);
+extern void *(* __malloc_hook)(size_t size);
+extern void *(* __realloc_hook)(void *ptr, size_t size);
+], [
+  void *ptr = 0L;
+  if (__malloc_hook) ptr = __malloc_hook(1);
+  if (__realloc_hook) ptr = __realloc_hook(ptr, 2);
+  if (__free_hook && ptr) __free_hook(ptr);
+], [je_cv_glibc_malloc_hook])
+if test "x${je_cv_glibc_malloc_hook}" = "xyes" ; then
+  AC_DEFINE([JEMALLOC_GLIBC_MALLOC_HOOK], [ ])
+fi
+
+JE_COMPILABLE([glibc memalign hook], [
+#include <stddef.h>
+
+extern void *(* __memalign_hook)(size_t alignment, size_t size);
+], [
+  void *ptr = 0L;
+  if (__memalign_hook) ptr = __memalign_hook(16, 7);
+], [je_cv_glibc_memalign_hook])
+if test "x${je_cv_glibc_memalign_hook}" = "xyes" ; then
+  AC_DEFINE([JEMALLOC_GLIBC_MEMALIGN_HOOK], [ ])
+fi
+
 dnl ============================================================================
 dnl Check for typedefs, structures, and compiler characteristics.
 AC_HEADER_STDBOOL

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -209,4 +209,10 @@
 /* sizeof(intmax_t) == 2^LG_SIZEOF_INTMAX_T. */
 #undef LG_SIZEOF_INTMAX_T
 
+/* glibc malloc hooks (__malloc_hook, __realloc_hook, __free_hook) */
+#undef JEMALLOC_GLIBC_MALLOC_HOOK
+
+/* glibc memalign hook */
+#undef JEMALLOC_GLIBC_MEMALIGN_HOOK
+
 #endif /* JEMALLOC_INTERNAL_DEFS_H_ */

src/jemalloc.c

@@ -1336,7 +1336,7 @@ je_valloc(size_t size)
 #define	is_malloc_(a) malloc_is_ ## a
 #define	is_malloc(a) is_malloc_(a)
 
-#if ((is_malloc(je_malloc) == 1) && defined(__GLIBC__) && !defined(__UCLIBC__))
+#if ((is_malloc(je_malloc) == 1) && defined(JEMALLOC_GLIBC_MALLOC_HOOK))
 /*
  * glibc provides the RTLD_DEEPBIND flag for dlopen which can make it possible
  * to inconsistently reference libc's malloc(3)-compatible functions
@@ -1349,8 +1349,10 @@ je_valloc(size_t size)
 JEMALLOC_EXPORT void (*__free_hook)(void *ptr) = je_free;
 JEMALLOC_EXPORT void *(*__malloc_hook)(size_t size) = je_malloc;
 JEMALLOC_EXPORT void *(*__realloc_hook)(void *ptr, size_t size) = je_realloc;
+# ifdef JEMALLOC_GLIBC_MEMALIGN_HOOK
 JEMALLOC_EXPORT void *(*__memalign_hook)(size_t alignment, size_t size) =
     je_memalign;
+# endif
 #endif
 
 /*