Re: [PATCH] warnings: address -Wnull-dereference in reader.c

[Akim Demaille]

> Le 8 juil. 2018 à 20:08, David Michael <address@hidden> a écrit :
> 
> This corrects a build failure when using GCC8 and configured with
> the --enable-gcc-warnings and --enable-assert options:

hi David, thanks!

I will install this slightly different version of your patch:

commit bda804d42aaf03c11869cfb1e0818d416d27b22c
Author: Akim Demaille <address@hidden>
Date:   Sun Aug 5 16:29:00 2018 +0200

    warnings: address -Wnull-dereference in reader.c
    
    Based on a patch by David Michael.
    http://lists.gnu.org/archive/html/bison-patches/2018-07/msg00000.html
    
    * src/reader.c (find_start): New, extracted from...
    (check_and_convert_grammar): here.

diff --git a/THANKS b/THANKS
index 74f04dd4..9d37dc84 100644
--- a/THANKS
+++ b/THANKS
@@ -39,6 +39,7 @@ Daniel Galloway           address@hidden
 Daniel Hagerty            address@hidden
 David J. MacKenzie        address@hidden
 David Kastrup             address@hidden
+David Michael             address@hidden
 Dennis Clarke             address@hidden
 Derek Clegg               address@hidden
 Derek M. Jones            address@hidden
diff --git a/src/reader.c b/src/reader.c
index 975f7c8d..153326d6 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -723,6 +723,25 @@ prepare_percent_define_front_end_variables (void)
   }
 }
 
+/* Find the first LHS which is not a dummy.  */
+static symbol *
+find_start ()
+{
+  symbol_list *res = grammar;
+  for (;
+       res != NULL && symbol_is_dummy (res->content.sym);
+       res = res->next)
+    {
+      for (res = res->next;
+           res != NULL && res->content.sym != NULL;
+           res = res->next)
+        continue;
+      aver (res != NULL);
+    }
+  aver (res != NULL);
+  return res->content.sym;
+}
+
 
 /*-------------------------------------------------------------.
 | Check the grammar that has just been read, and convert it to |
@@ -749,22 +768,12 @@ check_and_convert_grammar (void)
   /* Report any undefined symbols and consider them nonterminals.  */
   symbols_check_defined ();
 
-  /* Find the start symbol if no %start.  */
+  /* Find the start symbol if no %start: the first LHS which is not a
+     dummy.  */
   if (!start_flag)
     {
-      symbol_list *node;
-      for (node = grammar;
-           node != NULL && symbol_is_dummy (node->content.sym);
-           node = node->next)
-        {
-          for (node = node->next;
-               node != NULL && node->content.sym != NULL;
-               node = node->next)
-            continue;
-        }
-      aver (node != NULL);
-      grammar_start_symbol_set (node->content.sym,
-                                node->content.sym->location);
+      symbol *start = find_start ();
+      grammar_start_symbol_set (start, start->location);
     }
 
   /* Insert the initial rule, whose line is that of the first rule