Patchwork PR c++/47208

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Submitter Dodji Seketeli
Date Feb. 17, 2011, 7:39 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/83473/
State New
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Dodji Seketeli - Feb. 17, 2011, 7:39 p.m.

Consider this short example invalid example:

 constexpr auto list = { };
 static const int l = list.size();

It lacks a '#include <initializer_list>' and so it makes G++ crash.

As 'list' cannot be initialized the type of its DECL is set to
error_mark_node. Then at some point finish_id_expression passes that
DECL to decl_constant_var_p that chokes because DECL is erroneous and
breaks one of its invariants.

The patch below just avoids passing an erroneous DECL to

The other hunk of the patch is because we get an additional diagnostic
that says.

  unable to deduce ‘<type error>’ from ‘<brace-enclosed initializer list>() 

I find the <type error> there being less than helpful to the user so I
thought maybe we could avoid displaying that message if the type we are
issuing the diagnostic about is error_mark_node. We then just get the
diagnostic message:

  "deducing from brace-enclosed initializer list requires #include <initializer_list>"

Which I believe is enough to understand what is going on.

Tested on x86_64-unknown-linux-gnu against trunk.
Jason Merrill - Feb. 17, 2011, 8:22 p.m.



diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 02b8d15..4990636 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -18926,7 +18926,11 @@  do_auto_deduction (tree type, tree init, tree auto_node)
   if (val > 0)
-      error ("unable to deduce %qT from %qE", type, init);
+      if (type && type != error_mark_node)
+	/* If type is error_mark_node a diagnostic must have been
+	   emitted by now.  Also, having a mention to '<type error>'
+	   in the diagnostic is not really useful to the user.  */
+	error ("unable to deduce %qT from %qE", type, init);
       return error_mark_node;
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index daa7280..1ad707b 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3148,7 +3148,8 @@  finish_id_expression (tree id_expression,
       /* Only certain kinds of names are allowed in constant
 	 expression.  Enumerators and template parameters have already
 	 been handled above.  */
-      if (integral_constant_expression_p
+      if (! error_operand_p (decl)
+	  && integral_constant_expression_p
 	  && ! decl_constant_var_p (decl)
 	  && ! builtin_valid_in_constant_expr_p (decl))
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto21.C b/gcc/testsuite/g++.dg/cpp0x/auto21.C
new file mode 100644
index 0000000..1cbcac5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto21.C
@@ -0,0 +1,5 @@ 
+// Origin PR c++/47208
+// { dg-options "-std=c++0x" }
+constexpr auto list = { }; // { dg-error "deducing from brace-enclosed initializer list requires #include <initializer_list>" }
+static const int l = list.size();