[cexpr] Add string and voidptr types

The string type is useful for passing around strings (the only thing
that they can do, currently), particularly as arguments to functions.
The voidptr type is (currently) never generated by the core cexpr
system, but is useful for storing pointers via cexpr (probably a bit of
a hack, but it seems to work well in my current use).

include/QF/cexpr.h

@@ -151,6 +151,9 @@ extern exprtype_t cexpr_exprval;
 extern exprtype_t cexpr_field;
 extern exprtype_t cexpr_function;
 extern exprtype_t cexpr_plitem;
+extern exprtype_t cexpr_string;
+// generic pointer holder, never generated directly by cexpr
+extern exprtype_t cexpr_voidptr;
 
 extern binop_t cexpr_array_binops[];
 extern binop_t cexpr_struct_binops[];

libs/util/cexpr-lex.l

@@ -76,6 +76,7 @@ static exprval_t *parse_uint (const char *str, exprctx_t *context);
 static exprval_t *parse_size_t (const char *str, exprctx_t *context);
 static exprval_t *parse_float (const char *str, exprctx_t *context);
 static exprval_t *parse_double (const char *str, exprctx_t *context);
+static exprval_t *parse_string (const char *str, exprctx_t *context);
 static exprsym_t *parse_name (const char *str, exprctx_t *context);
 static exprval_t *parse_variable (const char *str, exprctx_t *context);
 
@@ -174,6 +175,8 @@ STRING		\"(\\.|[^"\\])*\"
 					}
 
 {STRING}			{
+						yylval->value = parse_string (yytext, context);
+						return VALUE;
 					}
 @					return '@';
 
@@ -292,6 +295,19 @@ static exprval_t *parse_double (const char *str, exprctx_t *context)
 	return val;
 }
 
+static exprval_t *parse_string (const char *str, exprctx_t *context)
+{
+	exprval_t  *val = cexpr_value (&cexpr_string, context);
+	// str includes the quotes, which add 2 to the length of the string, but
+	// only one byte is needed for the terminating nul
+	size_t      size = strlen (str) - 1;
+	char       *dup = cmemalloc (context->memsuper, size);
+	strncpy (dup, str + 1, size - 1);
+	dup[size - 1] = 0;
+	*(char **) val->value = dup;
+	return val;
+}
+
 static exprsym_t *
 parse_name (const char *name, exprctx_t *context)
 {

libs/util/cexpr-type.c

@@ -774,6 +774,16 @@ exprtype_t cexpr_plitem = {
 	.unops = 0,
 };
 
+exprtype_t cexpr_string = {
+	.name = "string",
+	.size = sizeof (char *),
+};
+
+exprtype_t cexpr_voidptr = {
+	.name = "voidptr",
+	.size = sizeof (void *),
+};
+
 VISIBLE binop_t *
 cexpr_find_cast (exprtype_t *dst_type, exprtype_t *src_type)
 {