Port to FreeBSD 11 AMD

Problem reported by Ashish Shukla (Bug#24892).  I tested
this on FreeBSD 11 x86-64 with HAVE_SBRK manually undefined.
* configure.ac (system_malloc): Set to 'yes' if there is no sbrk.
(sbrk): Check whether it exists.
* src/alloc.c (my_heap_start) [!GNU_LINUX]:
Do not define, since this function is now used only on GNU/Linux,
and sbrk might not exist on other platforms.
(malloc_initialize_hook) [!GNU_LINUX]:
Do not call my_heap_start, since its side effect will never be used.
(Fmemory_limit) [!HAVE_SBRK]: Do not call sbrk.
* src/unexelf.c (unexec) [!HAVE_SBRK]: Assume that nothing like
sbrk exists.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index a58dc13cbd7..90c6f9441fa 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -97,7 +97,7 @@ static bool valgrind_p;
 #include "w32heap.h"    /* for sbrk */
 #endif
 
-#if defined DOUG_LEA_MALLOC || defined GNU_LINUX
+#ifdef GNU_LINUX
 /* The address where the heap starts.  */
 void *
 my_heap_start (void)
@@ -130,7 +130,9 @@ malloc_initialize_hook (void)
 
   if (! initialized)
     {
+#ifdef GNU_LINUX
       my_heap_start ();
+#endif
       malloc_using_checking = getenv ("MALLOC_CHECK_") != NULL;
     }
   else
@@ -7053,7 +7055,7 @@ We divide the value by 1024 to make sure it fits in a Lisp integer.  */)
 {
   Lisp_Object end;
 
-#ifdef HAVE_NS
+#if defined HAVE_NS || !HAVE_SBRK
   /* Avoid warning.  sbrk has no relation to memory allocated anyway.  */
   XSETINT (end, 0);
 #else