From 89eb9e8002466f3099de77bc42cdabbf67d5dc1b Mon Sep 17 00:00:00 2001
From: Florian Diebold <florian.diebold@freiheit.com>
Date: Fri, 13 Mar 2020 13:57:44 +0100
Subject: [PATCH] Protect against infinite macro expansion in def collector

There was a test for this, but it wasn't actually working because the first
recursive expansion failed. (The comma...)

Even with this limit, that test (when fixed) still takes some time to pass
because of the exponential growth of the expansions, so I disabled it and added
a different one without growth.
---
 crates/ra_hir_def/src/nameres/collector.rs | 48 ++++++++++++++++++----
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index d0459d9b099b..db9838cb5e43 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -102,6 +102,7 @@ struct MacroDirective {
     module_id: LocalModuleId,
     ast_id: AstIdWithPath<ast::MacroCall>,
     legacy: Option<MacroCallId>,
+    depth: usize,
 }
 
 #[derive(Clone, Debug, Eq, PartialEq)]
@@ -134,6 +135,7 @@ fn collect(&mut self) {
         self.def_map.modules[module_id].origin = ModuleOrigin::CrateRoot { definition: file_id };
         ModCollector {
             def_collector: &mut *self,
+            macro_depth: 0,
             module_id,
             file_id: file_id.into(),
             raw_items: &raw_items,
@@ -516,7 +518,7 @@ fn resolve_macros(&mut self) -> ReachedFixedPoint {
         macros.retain(|directive| {
             if let Some(call_id) = directive.legacy {
                 res = ReachedFixedPoint::No;
-                resolved.push((directive.module_id, call_id));
+                resolved.push((directive.module_id, call_id, directive.depth));
                 return false;
             }
 
@@ -530,7 +532,7 @@ fn resolve_macros(&mut self) -> ReachedFixedPoint {
                 );
                 resolved_res.resolved_def.take_macros()
             }) {
-                resolved.push((directive.module_id, call_id));
+                resolved.push((directive.module_id, call_id, directive.depth));
                 res = ReachedFixedPoint::No;
                 return false;
             }
@@ -541,7 +543,7 @@ fn resolve_macros(&mut self) -> ReachedFixedPoint {
             if let Some(call_id) =
                 directive.ast_id.as_call_id(self.db, |path| self.resolve_attribute_macro(&path))
             {
-                resolved.push((directive.module_id, call_id));
+                resolved.push((directive.module_id, call_id, 0));
                 res = ReachedFixedPoint::No;
                 return false;
             }
@@ -552,8 +554,12 @@ fn resolve_macros(&mut self) -> ReachedFixedPoint {
         self.unexpanded_macros = macros;
         self.unexpanded_attribute_macros = attribute_macros;
 
-        for (module_id, macro_call_id) in resolved {
-            self.collect_macro_expansion(module_id, macro_call_id);
+        for (module_id, macro_call_id, depth) in resolved {
+            if depth > 1024 {
+                log::debug!("Max macro expansion depth reached");
+                continue;
+            }
+            self.collect_macro_expansion(module_id, macro_call_id, depth);
         }
 
         res
@@ -573,12 +579,18 @@ fn resolve_attribute_macro(&self, path: &ModPath) -> Option<MacroDefId> {
         None
     }
 
-    fn collect_macro_expansion(&mut self, module_id: LocalModuleId, macro_call_id: MacroCallId) {
+    fn collect_macro_expansion(
+        &mut self,
+        module_id: LocalModuleId,
+        macro_call_id: MacroCallId,
+        depth: usize,
+    ) {
         let file_id: HirFileId = macro_call_id.as_file();
         let raw_items = self.db.raw_items(file_id);
         let mod_dir = self.mod_dirs[&module_id].clone();
         ModCollector {
             def_collector: &mut *self,
+            macro_depth: depth,
             file_id,
             module_id,
             raw_items: &raw_items,
@@ -595,6 +607,7 @@ fn finish(self) -> CrateDefMap {
 /// Walks a single module, populating defs, imports and macros
 struct ModCollector<'a, D> {
     def_collector: D,
+    macro_depth: usize,
     module_id: LocalModuleId,
     file_id: HirFileId,
     raw_items: &'a raw::RawItems,
@@ -684,6 +697,7 @@ fn collect_module(&mut self, module: &raw::ModuleData, attrs: &Attrs) {
 
                 ModCollector {
                     def_collector: &mut *self.def_collector,
+                    macro_depth: self.macro_depth,
                     module_id,
                     file_id: self.file_id,
                     raw_items: self.raw_items,
@@ -713,6 +727,7 @@ fn collect_module(&mut self, module: &raw::ModuleData, attrs: &Attrs) {
                         let raw_items = self.def_collector.db.raw_items(file_id.into());
                         ModCollector {
                             def_collector: &mut *self.def_collector,
+                            macro_depth: self.macro_depth,
                             module_id,
                             file_id: file_id.into(),
                             raw_items: &raw_items,
@@ -887,6 +902,7 @@ fn collect_macro(&mut self, mac: &raw::MacroData) {
                 module_id: self.module_id,
                 ast_id,
                 legacy: Some(macro_call_id),
+                depth: self.macro_depth + 1,
             });
 
             return;
@@ -902,6 +918,7 @@ fn collect_macro(&mut self, mac: &raw::MacroData) {
             module_id: self.module_id,
             ast_id,
             legacy: None,
+            depth: self.macro_depth + 1,
         });
     }
 
@@ -971,13 +988,26 @@ fn do_resolve(code: &str) -> CrateDefMap {
     }
 
     #[test]
-    fn test_macro_expand_will_stop() {
+    fn test_macro_expand_will_stop_1() {
         do_resolve(
             r#"
         macro_rules! foo {
-            ($($ty:ty)*) => { foo!($($ty)*, $($ty)*); }
+            ($($ty:ty)*) => { foo!($($ty)*); }
         }
-foo!(KABOOM);
+        foo!(KABOOM);
+        "#,
+        );
+    }
+
+    #[ignore] // this test does succeed, but takes quite a while :/
+    #[test]
+    fn test_macro_expand_will_stop_2() {
+        do_resolve(
+            r#"
+        macro_rules! foo {
+            ($($ty:ty)*) => { foo!($($ty)* $($ty)*); }
+        }
+        foo!(KABOOM);
         "#,
         );
     }