Hi,
a while ago I noticed that in cp_parser_binary_expression we were
calling cp_fully_fold first to disable the warnings for not executed
expressions, and then, seemingly in a very redundant and inconsistent
with other situations way, to re-enable the warnings (*). Thus, I meant
to investigate opportunities for a mini optimization / clean-up during
the next Stage 1.
However, over the last couple of weeks I noticed that we had in Bugzilla
a number of error-recovery regressions happening starting from the
*second* cp_fully_fold calls, those which likely could be completely
avoided. Note, not only we were calling again cp_fully_fold, we were
also doing that for expressions which could not be folded to true/false
the first time we tried, error-prone and wasteful too.
Then the below which seems rather straightforward to me. To be
super-safe I carried out a number of additional checks and instrumented
testsuite runs: that we exercise the code enough; that when we set
disable_warnings_sp = sp we find it NULL, etc. Everything went well..
Tested x86_64-linux.
Thanks, Paolo.
(*) Historically, we used not to have this disabling code at all, then a
very basic version not folding.
/////////////////
/cp
2019-03-25 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/84661
PR c++/85013
* parser.c (cp_parser_binary_expression): Don't call cp_fully_fold
to undo the disabling of warnings.
/testsuite
2019-03-25 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/84661
PR c++/85013
* g++.dg/concepts/pr84661.C: New.
* g++.dg/torture/pr85013.C: Likewise.
Index: cp/parser.c
===================================================================
--- cp/parser.c (revision 269881)
+++ cp/parser.c (working copy)
@@ -9443,6 +9443,7 @@ cp_parser_binary_expression (cp_parser* parser, bo
{
cp_parser_expression_stack stack;
cp_parser_expression_stack_entry *sp = &stack[0];
+ cp_parser_expression_stack_entry *disable_warnings_sp = NULL;
cp_parser_expression_stack_entry current;
cp_expr rhs;
cp_token *token;
@@ -9506,12 +9507,14 @@ cp_parser_binary_expression (cp_parser* parser, bo
/* For "false && x" or "true || x", x will never be executed;
disable warnings while evaluating it. */
- if (current.tree_type == TRUTH_ANDIF_EXPR)
- c_inhibit_evaluation_warnings +=
- cp_fully_fold (current.lhs) == truthvalue_false_node;
- else if (current.tree_type == TRUTH_ORIF_EXPR)
- c_inhibit_evaluation_warnings +=
- cp_fully_fold (current.lhs) == truthvalue_true_node;
+ if ((current.tree_type == TRUTH_ANDIF_EXPR
+ && cp_fully_fold (current.lhs) == truthvalue_false_node)
+ || (current.tree_type == TRUTH_ORIF_EXPR
+ && cp_fully_fold (current.lhs) == truthvalue_true_node))
+ {
+ disable_warnings_sp = sp;
+ ++c_inhibit_evaluation_warnings;
+ }
/* Extract another operand. It may be the RHS of this expression
or the LHS of a new, higher priority expression. */
@@ -9557,12 +9560,11 @@ cp_parser_binary_expression (cp_parser* parser, bo
}
/* Undo the disabling of warnings done above. */
- if (current.tree_type == TRUTH_ANDIF_EXPR)
- c_inhibit_evaluation_warnings -=
- cp_fully_fold (current.lhs) == truthvalue_false_node;
- else if (current.tree_type == TRUTH_ORIF_EXPR)
- c_inhibit_evaluation_warnings -=
- cp_fully_fold (current.lhs) == truthvalue_true_node;
+ if (sp == disable_warnings_sp)
+ {
+ disable_warnings_sp = NULL;
+ --c_inhibit_evaluation_warnings;
+ }
if (warn_logical_not_paren
&& TREE_CODE_CLASS (current.tree_type) == tcc_comparison
Index: testsuite/g++.dg/concepts/pr84661.C
===================================================================
--- testsuite/g++.dg/concepts/pr84661.C (nonexistent)
+++ testsuite/g++.dg/concepts/pr84661.C (working copy)
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-fconcepts" }
+
+struct S {
+ int &a;
+ void foo (decltype(((a = 0) || ((auto))))); // { dg-error "expected" }
+};
Index: testsuite/g++.dg/torture/pr85013.C
===================================================================
--- testsuite/g++.dg/torture/pr85013.C (nonexistent)
+++ testsuite/g++.dg/torture/pr85013.C (working copy)
@@ -0,0 +1,3 @@
+// { dg-additional-options "-std=c++14 -fconcepts" }
+
+a(decltype((0 > 1e91 && 1e31 && (auto)))); // { dg-error "expected" }
