Add new function `malloc-trim'

* configure.ac (PGTK_LIBS): Check for malloc_trim.

* src/alloc.c (Fmalloc_trim): Add new function (bug#45200).

1 files changed, 34 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
index b9712859c38..661f37dd5cc 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -7479,6 +7479,37 @@ arenas.  */)
 }
 #endif
 
+#ifdef HAVE_MALLOC_TRIM
+DEFUN ("malloc-trim", Fmalloc_trim, Smalloc_trim, 0, 1, "",
+       doc: /* Release free memory from the heap.
+This function asks libc to return unused memory back to the operating
+system.  This function isn't guaranteed to do anything, and is mainly
+meant as a debugging tool.
+
+If LEAVE_PADDING is given, ask the system to leave that much unused
+spaced in the heap.  This should be an integer, and if not given,
+defaults to 0.
+
+This function returns nil if no memory could be returned to the
+system, and non-nil if some memory could be returned.  */)
+  (Lisp_Object leave_padding)
+{
+  int pad = 0;
+
+  if (! NILP (leave_padding))
+    {
+      CHECK_FIXNAT (leave_padding);
+      pad = XFIXNUM (leave_padding);
+    }
+
+  /* 1 means that memory was released to the system.  */
+  if (malloc_trim (pad) == 1)
+    return Qt;
+  else
+    return Qnil;
+}
+#endif
+
 static bool
 symbol_uses_obj (Lisp_Object symbol, Lisp_Object obj)
 {
@@ -7830,6 +7861,9 @@ N should be nonnegative.  */);
 
   defsubr (&Smalloc_info);
 #endif
+#ifdef HAVE_MALLOC_TRIM
+  defsubr (&Smalloc_trim);
+#endif
   defsubr (&Ssuspicious_object);
 
   Lisp_Object watcher;