From fee45935eb7f5a098cbbbaf1c8d1a8f9a77ce418 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?P=C3=A9ter=20G=C3=B6m=C3=B6ri?= Date: Sat, 9 Jul 2016 17:21:27 +0200 Subject: Fix infinite loop in merl_transform This can happen when a syntactically incorrect text is passed to a merl:qquote/2,/3 call. The parse transform optimizes calls to some functions in merl by converting strings into templates at compile time. If this evaluation fails (in eval_call/4 - for example because of a sytanx error in the parsed text) the original function call should be kept unchanged. However in case of qquote/3 the call is converted into a combination of quote/2 and subst/2, but upon failure the original qquote/3 call is substituted into the wrong place. E.g.: this expression merl:qquote(Pos, Text, Env) is first converted to merl:subst(merl:quote(Pos, Text), Env) then if evaluating the quote call fails into merl:subst(merl:qquote(Pos, Text, Env), Env) and the expansion is run again on the internal qquote/3 argument resulting in an infinite loop. This is now fixed so in case of failure the original qquote/3 call is kept. --- lib/syntax_tools/src/merl_transform.erl | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'lib/syntax_tools/src/merl_transform.erl') diff --git a/lib/syntax_tools/src/merl_transform.erl b/lib/syntax_tools/src/merl_transform.erl index fe58b6a122..497baddd0a 100644 --- a/lib/syntax_tools/src/merl_transform.erl +++ b/lib/syntax_tools/src/merl_transform.erl @@ -104,10 +104,15 @@ expand_qquote([Text, Env], T, Line) -> case erl_syntax:is_literal(Text) of true -> As = [Line, erl_syntax:concrete(Text)], - %% expand further if possible - expand(merl:qquote(Line, "merl:subst(_@tree, _@env)", - [{tree, eval_call(Line, quote, As, T)}, - {env, Env}])); + case eval_call(Line, quote, As, failed) of + failed -> + T; + T1 -> + %% expand further if possible + expand(merl:qquote(Line, "merl:subst(_@tree, _@env)", + [{tree, T1}, + {env, Env}])) + end; false -> T end; -- cgit v1.2.3