Variadic C functions now count arguments with ptrdiff_t.

This partly undoes my 2011-03-30 change, which replaced int with size_t.
Back then I didn't know that the Emacs coding style prefers signed int.
Also, in the meantime I found a few more instances where arguments
were being counted with int, which may truncate counts on 64-bit
machines, or EMACS_INT, which may be unnecessarily wide.
* lisp.h (struct Lisp_Subr.function.aMANY)
(DEFUN_ARGS_MANY, internal_condition_case_n, safe_call):
Arg counts are now ptrdiff_t, not size_t.
All variadic functions and their callers changed accordingly.
(struct gcpro.nvars): Now size_t, not size_t.  All uses changed.
* bytecode.c (exec_byte_code): Check maxdepth for overflow,
to avoid potential buffer overrun.  Don't assume arg counts fit in 'int'.
* callint.c (Fcall_interactively): Check arg count for overflow,
to avoid potential buffer overrun.  Use signed char, not 'int',
for 'varies' array, so that we needn't bother to check its size
calculation for overflow.
* editfns.c (Fformat): Use ptrdiff_t, not EMACS_INT, to count args.
* eval.c (apply_lambda):
* fns.c (Fmapconcat): Use XFASTINT, not XINT, to get args length.
(struct textprop_rec.argnum): Now ptrdiff_t, not int.  All uses changed.
(mapconcat): Use ptrdiff_t, not int and EMACS_INT, to count args.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/charset.c b/src/charset.c
index 29f98f24089..55234aa76aa 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -844,7 +844,7 @@ DEFUN ("define-charset-internal", Fdefine_charset_internal,
        Sdefine_charset_internal, charset_arg_max, MANY, 0,
        doc: /* For internal use only.
 usage: (define-charset-internal ...)  */)
-  (size_t nargs, Lisp_Object *args)
+  (ptrdiff_t nargs, Lisp_Object *args)
 {
   /* Charset attr vector.  */
   Lisp_Object attrs;
@@ -2145,11 +2145,11 @@ DEFUN ("set-charset-priority", Fset_charset_priority, Sset_charset_priority,
        1, MANY, 0,
        doc: /* Assign higher priority to the charsets given as arguments.
 usage: (set-charset-priority &rest charsets)  */)
-  (size_t nargs, Lisp_Object *args)
+  (ptrdiff_t nargs, Lisp_Object *args)
 {
   Lisp_Object new_head, old_list, arglist[2];
   Lisp_Object list_2022, list_emacs_mule;
-  size_t i;
+  ptrdiff_t i;
   int id;
 
   old_list = Fcopy_sequence (Vcharset_ordered_list);