preproc: add %count() function

Add %count(), giving a count of the number of arguments.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Author: H. Peter Anvin

asm/preproc.c

@@ -7013,6 +7013,16 @@ stdmac_cond_sel(const SMacro *s, Token **params, int nparams)
     return new_Token(NULL, tok_smac_param(which), "", 0);
 }
 
+/* %count() */
+static Token *
+stdmac_count(const SMacro *s, Token **params, int nparams)
+{
+    (void)s;
+    (void)params;
+
+    return make_tok_num(NULL, nparams);
+}
+
 /* Add magic standard macros */
 struct magic_macros {
     const char *name;
@@ -7028,6 +7038,7 @@ static void pp_add_magic_stdmac(void)
         { "__?LINE?__", true, 0, 0, stdmac_line },
         { "__?BITS?__", true, 0, 0, stdmac_bits },
         { "__?PTR?__",  true, 0, 0, stdmac_ptr },
+        { "%count",     false, 1, SPARM_VARADIC, stdmac_count },
         { "%eval",      false, 1, SPARM_EVAL|SPARM_VARADIC, stdmac_join },
         { "%str",       false, 1, SPARM_GREEDY|SPARM_STR, stdmac_join },
         { "%strcat",    false, 1, SPARM_GREEDY, stdmac_strcat },

doc/nasmdoc.src

@@ -2867,13 +2867,28 @@ to \c{%sel(2-!(x),y,z)}.
 The argument not selected is never expanded.
 
 
+\S{f_count} \i\c{%count()} Function
+
+The \c{%count()} function expands to the number of argments passed to
+the macro. Note that just as for single-line macros, \c{%count()}
+treats an empty argument list as a single empty argument.
+
+\c %xdefine empty %count()        ; %define empty 1
+\c %xdefine one   %count(1) 	  ; %define one 1
+\c %xdefine two   %count(5,q)	  ; %define two 2
+\c %define  list  a,b,46
+\c %xdefine lc1   %count(list)	  ; %define lc 1 (just one argument)
+\c %xdefine lc2   %count(%[list]) ; %define lc 3 (indirection expands)
+
+
 \S{f_eval} \i\c{%eval()} Function
 
 The \c{%eval()} function evaluates its argument as a numeric
-expression in much the same way the \i\c{%assign} directive would, see
-\k{assign}. Unlike \c{%assign}, \c{%eval()} supports more than one
-argument; if more than one argument is specified, it is expanded to a
-comma-separated list of values.
+expression and expands to the result as an integer constant in much
+the same way the \i\c{%assign} directive would, see \k{assign}. Unlike
+\c{%assign}, \c{%eval()} supports more than one argument; if more than
+one argument is specified, it is expanded to a comma-separated list of
+values.
 
 \c %assign a    2
 \c %assign b    3