[PATCH 5/9] lalr1.cc: fix exception safety

[Akim Demaille]

lalr1.cc does not reclaim its memory when ended by an exception.

Reported by Oleksii Taran:
http://lists.gnu.org/archive/html/help-bison/2012-09/msg00000.html

* data/lalr1.cc (yyparse): Protect the whole yyparse by a try-catch
block that cleans the stack and the lookahead.
---
 THANKS        |  1 +
 data/lalr1.cc | 45 ++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/THANKS b/THANKS
index 8af0abb..5a77c54 100644
--- a/THANKS
+++ b/THANKS
@@ -80,6 +80,7 @@ Nicolas Tisserand         address@hidden
 Noah Friedman             address@hidden
 Odd Arild Olsen           address@hidden
 Oleg Smolsky              address@hidden
+Oleksii Taran             address@hidden
 Paolo Bonzini             address@hidden
 Pascal Bart               address@hidden
 Paul Eggert               address@hidden
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 846aea1..fe23b3e 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -533,6 +533,10 @@ do {                                       \
 
     int yyresult;
 
+    // FIXME: This shoud be completely indented.  It is not yet to
+    // avoid gratuitous conflicts when merging into the master branch.
+    try
+      {
     YYCDEBUG << "Starting parse" << std::endl;
 
 ]m4_ifdef([b4_initial_action], [
@@ -573,14 +577,13 @@ b4_dollar_popdef])[]dnl
     /* Read a lookahead token.  */
     if (yychar == yyempty_)
       {
-       YYCDEBUG << "Reading a token: ";
-       yychar = ]b4_c_function_call([yylex], [int],
-                                    [b4_api_PREFIX[STYPE*], [&yylval]][]dnl
+        YYCDEBUG << "Reading a token: ";
+        yychar = ]b4_c_function_call([yylex], [int],
+                                     [b4_api_PREFIX[STYPE*], [&yylval]][]dnl
 b4_locations_if([, [[location*], [&yylloc]]])dnl
 m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
       }
 
-
     /* Convert token to internal form.  */
     if (yychar <= yyeof_)
       {
@@ -651,17 +654,21 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     else
       yyval = yysemantic_stack_[0];
 
+    // Compute the default @@$.
     {
       slice<location_type, location_stack_type> slice (yylocation_stack_, 
yylen);
       YYLLOC_DEFAULT (yyloc, slice, yylen);
     }
+
+    // Perform the reduction.
     YY_REDUCE_PRINT (yyn);
     switch (yyn)
       {
-       ]b4_user_actions[
-       default:
-          break;
+        ]b4_user_actions[
+      default:
+        break;
       }
+
     /* User semantic actions sometimes alter yychar, and that requires
        that yytoken be updated with the new translation.  We take the
        approach of translating immediately before every use of yytoken.
@@ -831,6 +838,30 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
       }
 
     return yyresult;
+    }
+    catch (...)
+      {
+        YYCDEBUG << "Exception caught" << std::endl;
+        if (yychar != yyempty_)
+          {
+            /* Make sure we have latest lookahead translation.  See
+               comments at user semantic actions for why this is
+               necessary.  */
+            yytoken = yytranslate_ (yychar);
+            yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval,
+                         &yylloc);
+          }
+
+        while (yystate_stack_.height () != 1)
+          {
+            yydestruct_ ("Cleanup: popping",
+                         yystos_[yystate_stack_[0]],
+                         &yysemantic_stack_[0],
+                         &yylocation_stack_[0]);
+            yypop_ ();
+          }
+        throw;
+      }
   }
 
   // Generate an error message.
-- 
1.7.12.2