[PATCH] c++: fix ICE with -Wduplicated-cond [PR107593]

[Marek Polacek]

Here we crash because a CAST_EXPR, representing T(), doesn't have
its operand, and operand_equal_p's STRIP_ANY_LOCATION_WRAPPER doesn't
expect that.  (o_e_p is called from warn_duplicated_cond_add_or_warn.)

In the past we've adjusted o_e_p to better cope with template codes,
but in this case I think we just want to avoid attempting to warn
about inst-dependent expressions; I don't think I've ever envisioned
-Wduplicated-cond to warn about them.

The ICE started with r12-6022, two-stage name lookup for overloaded
operators, which gave dependent operators a TREE_TYPE (in particular,
DEPENDENT_OPERATOR_TYPE), so we no longer bail out here in o_e_p:

  /* Similar, if either does not have a type (like a template id),
     they aren't equal.  */
  if (!TREE_TYPE (arg0) || !TREE_TYPE (arg1))
    return false;

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

	PR c++/107593

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_selection_statement): Don't do
	-Wduplicated-cond when the condition is dependent.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wduplicated-cond3.C: New test.
---
 gcc/cp/parser.cc                              |  3 +-
 gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C | 38 +++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 4cdc1cd472f..3df85d49e16 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -13209,7 +13209,8 @@ cp_parser_selection_statement (cp_parser* parser, bool *if_p,
 	    /* Add the condition.  */
 	    condition = finish_if_stmt_cond (condition, statement);
 
-	    if (warn_duplicated_cond)
+	    if (warn_duplicated_cond
+		&& !instantiation_dependent_expression_p (condition))
 	      warn_duplicated_cond_add_or_warn (token->location, condition,
 						&chain);
 
diff --git a/gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C b/gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C
new file mode 100644
index 00000000000..3da054e5485
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C
@@ -0,0 +1,38 @@
+// PR c++/107593
+// { dg-do compile }
+// { dg-options "-Wduplicated-cond" }
+
+template <typename T>
+void
+foo ()
+{
+  if (T() && T() && int())
+    ;
+  else if (T() && T() && int())
+    ;
+}
+
+template <typename T>
+void bar(T a)
+{
+  if (a)
+    ;
+  else if (a)
+    ;
+}
+
+template <typename>
+void baz(int a)
+{
+  if (a)
+    ;
+  else if (a) // { dg-warning "duplicated" }
+    ;
+}
+void
+f ()
+{
+  foo<int>();
+  bar(1);
+  baz<int>(1);
+}

base-commit: 94673a121cfc7f9d51c9d05e31795477f4dc8dc7
-- 
2.39.1