shithub: femtolisp

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read: fix a possible crash

If a gigantic expression is loaded, there is a high chance gc
kicked in before ios_eof got called on a non-updated pointer
(unfortunately).

Don't even need a gc handle here.

--- a/iostream.c

+++ b/iostream.c

@@ -117,20 +117,13 @@

 BUILTIN("read", read)

 {

-	value_t arg = 0;

 	if(nargs > 1)

 		argcount(nargs, 1);

-	else if(nargs == 0)

-		arg = symbol_value(FL(instrsym));

-	else

-		arg = args[0];

-	ios_t *s = toiostream(arg);

-	fl_gc_handle(&arg);

-	value_t v = fl_read_sexpr(arg);

-	fl_free_gc_handles(1);

-	if(ios_eof(s))

-		return FL(eof);

-	return v;

+	value_t a = nargs == 0 ? symbol_value(FL(instrsym)) : args[0];

+	USED(toiostream(a));

+	value_t v = fl_read_sexpr(a);

+	a = nargs == 0 ? symbol_value(FL(instrsym)) : args[0];

+	return ios_eof(toiostream(a)) ? FL(eof) : v;

 }

 BUILTIN("io-getc", io_getc)