Re: mem_insert, etc

[Gerd Moellmann]

Richard Stallman <address@hidden> writes:

> Could someone please document with comments in alloc.c the overall
> purpose of lisp_malloc, and mem_insert and friends?  All it says about
> mem_insert and friends is that they are "for stack marking", but it does
> not say how they relate to it or why they exist.

I've added the comment below.

Index: alloc.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/alloc.c,v
retrieving revision 1.258
diff -c -c -r1.258 alloc.c
*** alloc.c     16 Dec 2001 21:52:36 -0000      1.258
--- alloc.c     29 Dec 2001 12:46:54 -0000
***************
*** 2711,2716 ****
--- 2711,2727 ----
  
  #if GC_MARK_STACK || defined GC_MALLOC_CHECK
  
+ /* Conservative C stack marking requires a method to identify possibly
+    live Lisp objects given a pointer value.  We do this by keeping
+    track of blocks of Lisp data that are allocated in a red-black tree
+    (see also the comment of mem_node which is the type of nodes in
+    that tree).  Function lisp_malloc adds information for an allocated
+    block to the red-black tree with calls to mem_insert, and function
+    lisp_free removes it with mem_delete.  Functions live_string_p etc
+    call mem_find to lookup information about a given pointer in the
+    tree, and use that to determine if the pointer points to a Lisp
+    object or not.  */
+ 
  /* Initialize this part of alloc.c.  */
  
  static void