Go patch committed: Fix bug in unordered set when exporting
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Message ID CAOyqgcVcM-g+-m0yWOWtB_9qvA+1BR3fxZZ-PV1RPx3-Fe1uyg@mail.gmail.com
State New
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  • Go patch committed: Fix bug in unordered set when exporting
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Commit Message

Ian Lance Taylor July 18, 2019, 5:05 a.m. UTC
This Go frontend patch by Than McIntosh fixes a bug in the handling of
unordered set during exporting.

In https://golang.org/cl/183850
(https://gcc.gnu.org/ml/gcc-patches/2019-07/msg00200.html) a change
was made to combine tracking/discovery of exported types and imported
packages during export data generation.  As a result of this
refactoring a bug was introduced: the new code can potentially insert
items into the exports set (an unordered_set) while iterating through
the same set, which is illegal according to the spec for
std::unordered_set.

This patch fixes the problem by changing the type discovery phase to
iterate through a separate list of sorted exports, as opposed to
iterating through the main unordered set.  Also included is a change
to fix the code that looks for variables that are referenced from
inlined routine bodies (this code wasn't scanning all of the function
that it needed to scan).

There is a new test case for this problem in https://golang.org/cl/186697.

This is for https://golang.org/issue/33020.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Patch
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Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE	(revision 273534)
+++ gcc/go/gofrontend/MERGE	(working copy)
@@ -1,4 +1,4 @@ 
-0e51b7e9c03c6f6bc3d06343f2050f17349ccdc3
+19ed722fb3ae5e618c746da20efb79fc837337cd
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/export.cc
===================================================================
--- gcc/go/gofrontend/export.cc	(revision 273534)
+++ gcc/go/gofrontend/export.cc	(working copy)
@@ -111,7 +111,7 @@  class Collect_export_references : public
     : Traverse(traverse_expressions
                | traverse_types),
       exp_(exp), exports_(exports), imports_(imports),
-      inline_fcn_worklist_(NULL)
+      inline_fcn_worklist_(NULL), exports_finalized_(false)
   { }
 
   // Initial entry point; performs a walk to expand the exports set.
@@ -121,7 +121,7 @@  class Collect_export_references : public
   // Second entry point (called after the method above), to find
   // all types referenced by exports.
   void
-  prepare_types();
+  prepare_types(const std::vector<Named_object*>& sorted_exports);
 
  protected:
   // Override of parent class method.
@@ -141,6 +141,13 @@  class Collect_export_references : public
   traverse_named_type(Named_type*);
 
  private:
+
+  // Add a named object to the exports set (during expand_exports()).
+  // Returns TRUE if a new object was added to the exports set,
+  // FALSE otherwise.
+  bool
+  add_to_exports(Named_object*);
+
   // The exporter.
   Export* exp_;
   // The set of named objects to export.
@@ -152,6 +159,8 @@  class Collect_export_references : public
   // Worklist of functions we are exporting with inline bodies that need
   // to be checked.
   std::vector<Named_object*>* inline_fcn_worklist_;
+  // Set to true if expand_exports() has been called and is complete.
+  bool exports_finalized_;
 };
 
 void
@@ -172,6 +181,18 @@  Collect_export_references::expand_export
 	}
     }
   this->inline_fcn_worklist_ = NULL;
+  this->exports_finalized_ = true;
+}
+
+bool
+Collect_export_references::add_to_exports(Named_object* no)
+{
+  std::pair<Unordered_set(Named_object*)::iterator, bool> ins =
+      this->exports_->insert(no);
+  // If the export list has been finalized, then we should not be
+  // adding anything new to the exports set.
+  go_assert(!this->exports_finalized_ || !ins.second);
+  return ins.second;
 }
 
 int
@@ -189,7 +210,7 @@  Collect_export_references::expression(Ex
           if (var_package != NULL)
             this->imports_->insert(var_package);
 
-	  this->exports_->insert(no);
+	  this->add_to_exports(no);
 	  no->var_value()->set_is_referenced_by_inline();
 	}
       return TRAVERSE_CONTINUE;
@@ -210,17 +231,16 @@  Collect_export_references::expression(Ex
 
       if (this->inline_fcn_worklist_ != NULL)
         {
-          std::pair<Unordered_set(Named_object*)::iterator, bool> ins =
-              this->exports_->insert(no);
+          bool added = this->add_to_exports(no);
 
           if (no->is_function())
             no->func_value()->set_is_referenced_by_inline();
 
-          // If ins.second is false then this object was already in
+          // If 'added' is false then this object was already in
           // exports_, in which case it was already added to
           // check_inline_refs_ the first time we added it to exports_, so
           // we don't need to add it again.
-          if (ins.second
+          if (added
               && no->is_function()
               && no->func_value()->export_for_inlining())
             this->inline_fcn_worklist_->push_back(no);
@@ -238,11 +258,11 @@  Collect_export_references::expression(Ex
 // exported inline function from another package).
 
 void
-Collect_export_references::prepare_types()
+Collect_export_references::prepare_types(const std::vector<Named_object*>& sorted_exports)
 {
   // Iterate through the exported objects and traverse any types encountered.
-  for (Unordered_set(Named_object*)::iterator p = this->exports_->begin();
-       p != this->exports_->end();
+  for (std::vector<Named_object*>::const_iterator p = sorted_exports.begin();
+       p != sorted_exports.end();
        ++p)
     {
       Named_object* no = *p;
@@ -506,7 +526,8 @@  Export::export_globals(const std::string
 		       const std::map<std::string, Package*>& imports,
 		       const std::string& import_init_fn,
                        const Import_init_set& imported_init_fns,
-		       const Bindings* bindings)
+		       const Bindings* bindings,
+                       Unordered_set(Named_object*)* functions_marked_inline)
 {
   // If there have been any errors so far, don't try to export
   // anything.  That way the export code doesn't have to worry about
@@ -520,35 +541,21 @@  Export::export_globals(const std::string
   // CHECK_INLINE_REFS is also on EXPORTS.
   Unordered_set(Named_object*) exports;
   std::vector<Named_object*> check_inline_refs;
+  check_inline_refs.reserve(functions_marked_inline->size());
+
+  // Add all functions/methods from the "marked inlined" set to the
+  // CHECK_INLINE_REFS worklist.
+  for (Unordered_set(Named_object*)::const_iterator p = functions_marked_inline->begin();
+       p != functions_marked_inline->end();
+       ++p)
+      check_inline_refs.push_back(*p);
 
   for (Bindings::const_definitions_iterator p = bindings->begin_definitions();
        p != bindings->end_definitions();
        ++p)
     {
       if (should_export(*p))
-	{
-	  exports.insert(*p);
-
-	  if ((*p)->is_function()
-	      && (*p)->func_value()->export_for_inlining())
-	    check_inline_refs.push_back(*p);
-	  else if ((*p)->is_type())
-	    {
-	      const Bindings* methods = (*p)->type_value()->local_methods();
-	      if (methods != NULL)
-		{
-		  for (Bindings::const_definitions_iterator pm =
-			 methods->begin_definitions();
-		       pm != methods->end_definitions();
-		       ++pm)
-		    {
-		      Function* fn = (*pm)->func_value();
-		      if (fn->export_for_inlining())
-			check_inline_refs.push_back(*pm);
-		    }
-		}
-	    }
-	}
+        exports.insert(*p);
     }
 
   for (Bindings::const_declarations_iterator p =
@@ -593,7 +600,7 @@  Export::export_globals(const std::string
 
   // Collect up the set of types mentioned in things we're exporting,
   // and any packages that may be referred to indirectly.
-  collect.prepare_types();
+  collect.prepare_types(sorted_exports);
 
   // Assign indexes to all exported types and types referenced by
   // things we're exporting.  Return value is index of first non-exported
Index: gcc/go/gofrontend/export.h
===================================================================
--- gcc/go/gofrontend/export.h	(revision 273534)
+++ gcc/go/gofrontend/export.h	(working copy)
@@ -158,7 +158,8 @@  class Export : public String_dump
 		 const std::map<std::string, Package*>& imports,
 		 const std::string& import_init_fn,
 		 const Import_init_set& imported_init_fns,
-		 const Bindings* bindings);
+		 const Bindings* bindings,
+                 Unordered_set(Named_object*)* marked_inline_functions);
 
   // Record a type that is mentioned in export data. Return value is
   // TRUE for newly visited types, FALSE for types that have been seen
Index: gcc/go/gofrontend/gogo.cc
===================================================================
--- gcc/go/gofrontend/gogo.cc	(revision 273534)
+++ gcc/go/gofrontend/gogo.cc	(working copy)
@@ -5078,9 +5078,10 @@  Inline_within_budget::expression(Express
 class Mark_inline_candidates : public Traverse
 {
  public:
-  Mark_inline_candidates()
+  Mark_inline_candidates(Unordered_set(Named_object*)* marked)
     : Traverse(traverse_functions
-	       | traverse_types)
+	       | traverse_types),
+      marked_functions_(marked)
   { }
 
   int
@@ -5097,6 +5098,9 @@  class Mark_inline_candidates : public Tr
   // budget is a heuristic.  In the usual GCC spirit, we could
   // consider setting this via a command line option.
   const int budget_heuristic = 80;
+
+  // Set of named objects that are marked as inline candidates.
+  Unordered_set(Named_object*)* marked_functions_;
 };
 
 // Mark a function if it is an inline candidate.
@@ -5109,7 +5113,10 @@  Mark_inline_candidates::function(Named_o
   Inline_within_budget iwb(&budget);
   func->block()->traverse(&iwb);
   if (budget >= 0)
-    func->set_export_for_inlining();
+    {
+      func->set_export_for_inlining();
+      this->marked_functions_->insert(no);
+    }
   return TRAVERSE_CONTINUE;
 }
 
@@ -5135,7 +5142,10 @@  Mark_inline_candidates::type(Type* t)
       Inline_within_budget iwb(&budget);
       func->block()->traverse(&iwb);
       if (budget >= 0)
-	func->set_export_for_inlining();
+        {
+          func->set_export_for_inlining();
+          this->marked_functions_->insert(no);
+        }
     }
   return TRAVERSE_CONTINUE;
 }
@@ -5150,7 +5160,8 @@  Gogo::do_exports()
 
   // Mark any functions whose body should be exported for inlining by
   // other packages.
-  Mark_inline_candidates mic;
+  Unordered_set(Named_object*) marked_functions;
+  Mark_inline_candidates mic(&marked_functions);
   this->traverse(&mic);
 
   // For now we always stream to a section.  Later we may want to
@@ -5187,7 +5198,8 @@  Gogo::do_exports()
 		     this->imports_,
 		     init_fn_name,
 		     this->imported_init_fns_,
-		     this->package_->bindings());
+		     this->package_->bindings(),
+                     &marked_functions);
 
   if (!this->c_header_.empty() && !saw_errors())
     this->write_c_header();