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?

Ah that's unfortunate :( ISTM desirable to conservatively assume an
inst-dep cond has side effects though (possibly directly from
cp_parser_selection_statement), to avoid false positives as in:

   int n;

   template<class T> bool g() { n = 42; }

   template<class T>
   void f() {
     if (n)
       ;
     else if (g<T>())
       ;
     else if (n)
       ;
   }

You're right, we shouldn't warn there.  So I've just added a new param
with a default argument.  A new PR was just opened for the same problem
so I've added another test.

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 (warn_duplicated_cond_add_or_warn): New parameter.
        * c-warn.cc (warn_duplicated_cond_add_or_warn): Add new parameter.
        Use it.

gcc/cp/ChangeLog:

        * parser.cc (cp_parser_selection_statement): Pass the result of
        instantiation_dependent_expression_p down to
        warn_duplicated_cond_add_or_warn.

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                       |  3 +-
  gcc/c-family/c-warn.cc                        |  5 ++-
  gcc/cp/parser.cc                              |  8 +++-
  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 ++++++++
  6 files changed, 82 insertions(+), 5 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..a9b47e15894 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1514,7 +1514,8 @@ extern void maybe_record_typedef_use (tree);
  extern void maybe_warn_unused_local_typedefs (void);
  extern void maybe_warn_bool_compare (location_t, enum tree_code, tree, tree);
  extern bool maybe_warn_shift_overflow (location_t, tree, tree);
-extern void warn_duplicated_cond_add_or_warn (location_t, tree, vec<tree> **);
+extern void warn_duplicated_cond_add_or_warn (location_t, tree, vec<tree> **,
+                                             bool = false);
  extern bool diagnose_mismatched_attributes (tree, tree);
  extern tree do_warn_duplicated_branches_r (tree *, int *, void *);
  extern void warn_for_multistatement_macros (location_t, location_t,
diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index 5ed7bcab16a..b7621656f89 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -2529,13 +2529,14 @@ maybe_warn_unused_local_typedefs (void)
     of COND.  */
void
-warn_duplicated_cond_add_or_warn (location_t loc, tree cond, vec<tree> **chain)
+warn_duplicated_cond_add_or_warn (location_t loc, tree cond, vec<tree> **chain,
+                                 bool dependent_p /*=false*/)
  {
    /* No chain has been created yet.  Do nothing.  */
    if (*chain == NULL)
      return;
- if (TREE_SIDE_EFFECTS (cond))
+  if (dependent_p || TREE_SIDE_EFFECTS (cond))
      {
        /* Uh-oh!  This condition has a side-effect, thus invalidates
         the whole chain.  */
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 4cdc1cd472f..d62db229518 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -13210,8 +13210,12 @@ cp_parser_selection_statement (cp_parser* parser, bool 
*if_p,
            condition = finish_if_stmt_cond (condition, statement);
if (warn_duplicated_cond)
-             warn_duplicated_cond_add_or_warn (token->location, condition,
-                                               &chain);
+             {
+               const bool dep
+                 = instantiation_dependent_expression_p (condition);
+               warn_duplicated_cond_add_or_warn (token->location, condition,
+                                                 &chain, dep);
+             }
/* Parse the then-clause. */
            in_statement = parser->in_statement;
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: 5f8950b403f6351f125d8281d2e7430a43e7d125

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