[PATCH v3] c++: fix ICE with -Wduplicated-cond [PR107593]

[Marek Polacek <polacek@redhat.com>]

On Mon, Jan 30, 2023 at 01:12:00PM -0500, Jason Merrill wrote:
> On 1/30/23 11:00, Marek Polacek wrote:
> > On Fri, Jan 27, 2023 at 06:17:00PM -0500, Patrick Palka wrote:
> > > On Fri, 27 Jan 2023, Marek Polacek wrote:
> > > 
> > > > On Fri, Jan 27, 2023 at 05:15:00PM -0500, Patrick Palka wrote:
> > > > > On Thu, 26 Jan 2023, Marek Polacek via Gcc-patches wrote:
> > > > > 
> > > > > > 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);
> > > > > 
> > > > > I noticed warn_duplicated_cond_add_or_warn already has logic to handle
> > > > > TREE_SIDE_EFFECTS conditions by invaliding the entire chain.  I wonder
> > > > > if we'd want to do the same for instantiation-dep conditions?
> > > > 
> > > > warn_duplicated_cond_add_or_warn lives in c-family/c-warn.cc so I can't
> > > > use instantiation_dependent_expression_p there.  Sure, I could write a
> > > > C++ wrapper but with my patch we just won't add CONDITION to the chain
> > > > which I thought would work just as well.
> 
> Or maybe define instantiation_dependent_expression_p in the C front-end to
> just return false?

Like this?

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

-- >8 --
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.  Also destroy the chain when
an inst-dependent expression is encountered to not warn in
Wduplicated-cond4.C.

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;

	PR c++/107593
	PR c++/108597

gcc/c-family/ChangeLog:

	* c-common.h (instantiation_dependent_expression_p): Declare.
	* c-warn.cc (warn_duplicated_cond_add_or_warn): If the condition
	is dependent, invalidate the chain.

gcc/c/ChangeLog:

	* c-objc-common.cc (instantiation_dependent_expression_p): New.

gcc/cp/ChangeLog:

	* cp-tree.h (instantiation_dependent_expression_p): Don't
	declare here.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wduplicated-cond3.C: New test.
	* g++.dg/warn/Wduplicated-cond4.C: New test.
	* g++.dg/warn/Wduplicated-cond5.C: New test.
---
 gcc/c-family/c-common.h                       |  1 +
 gcc/c-family/c-warn.cc                        |  2 +-
 gcc/c/c-objc-common.cc                        |  8 ++++
 gcc/cp/cp-tree.h                              |  1 -
 gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C | 38 +++++++++++++++++++
 gcc/testsuite/g++.dg/warn/Wduplicated-cond4.C | 17 +++++++++
 gcc/testsuite/g++.dg/warn/Wduplicated-cond5.C | 16 ++++++++
 7 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wduplicated-cond3.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wduplicated-cond4.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wduplicated-cond5.C

diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index bb6271d4a83..2dadb33476c 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1101,6 +1101,7 @@ extern tree lookup_label (tree);
 extern tree lookup_name (tree);
 extern bool lvalue_p (const_tree);
 extern int maybe_adjust_arg_pos_for_attribute (const_tree);
+extern bool instantiation_dependent_expression_p (tree);
 
 extern bool vector_targets_convertible_p (const_tree t1, const_tree t2);
 extern bool vector_types_convertible_p (const_tree t1, const_tree t2, bool emit_lax_note);
diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index 5ed7bcab16a..29efce3f2c0 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -2535,7 +2535,7 @@ warn_duplicated_cond_add_or_warn (location_t loc, tree cond, vec<tree> **chain)
   if (*chain == NULL)
     return;
 
-  if (TREE_SIDE_EFFECTS (cond))
+  if (TREE_SIDE_EFFECTS (cond) || instantiation_dependent_expression_p (cond))
     {
       /* Uh-oh!  This condition has a side-effect, thus invalidates
 	 the whole chain.  */
diff --git a/gcc/c/c-objc-common.cc b/gcc/c/c-objc-common.cc
index d4f0b262ebb..0350733250b 100644
--- a/gcc/c/c-objc-common.cc
+++ b/gcc/c/c-objc-common.cc
@@ -400,3 +400,11 @@ maybe_adjust_arg_pos_for_attribute (const_tree)
 {
   return 0;
 }
+
+/* In C, no expression is dependent.  */
+
+bool
+instantiation_dependent_expression_p (tree)
+{
+  return false;
+}
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 9f188724cf2..31fd8af4f21 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7428,7 +7428,6 @@ extern bool any_type_dependent_arguments_p      (const vec<tree, va_gc> *);
 extern bool any_type_dependent_elements_p       (const_tree);
 extern bool type_dependent_expression_p_push	(tree);
 extern bool value_dependent_expression_p	(tree);
-extern bool instantiation_dependent_expression_p (tree);
 extern bool instantiation_dependent_uneval_expression_p (tree);
 extern bool any_value_dependent_elements_p      (const_tree);
 extern bool dependent_omp_for_p			(tree, tree, tree, tree);
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);
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wduplicated-cond4.C b/gcc/testsuite/g++.dg/warn/Wduplicated-cond4.C
new file mode 100644
index 00000000000..41bb9f09b4f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wduplicated-cond4.C
@@ -0,0 +1,17 @@
+// PR c++/107593
+// { dg-do compile }
+// { dg-options "-Wduplicated-cond" }
+
+int n;
+
+template<class T> bool g() { n = 42; return false; }
+
+template<class T>
+void f() {
+  if (n)
+    ;
+  else if (g<T>())
+    ;
+  else if (n)
+    ;
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wduplicated-cond5.C b/gcc/testsuite/g++.dg/warn/Wduplicated-cond5.C
new file mode 100644
index 00000000000..23a0bf212b5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wduplicated-cond5.C
@@ -0,0 +1,16 @@
+// PR c++/108597
+// { dg-do compile }
+// { dg-options "-Wduplicated-cond" }
+
+template <typename T>
+struct MyStruct {
+
+    void check(int &x) {
+        if (&x == &_a) {
+        } else if (&x == &_b) {
+        }
+    }
+
+    int _a;
+    int _b;
+};

base-commit: 897a0502056e6cc6613f26e0b22d1c1e06b1490f
-- 
2.39.1