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

[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

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

[Patrick Palka]

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?

>  
> 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
> 
> 

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

[Jason Merrill]

On 1/27/23 17:15, 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?

Makes sense.

>>   
>> 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
>>
>>
> 

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

[Marek Polacek]

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.

Marek

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

[Patrick Palka]

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.

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)
      ;
  }

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

[Patrick Palka]

On Fri, 27 Jan 2023, 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.
> 
> Ah that's unfortunate :( ISTM desirable to conservatively assume an
> inst-dep cond has side effects though (possibly directly from

oops, "has side effects and clear the chain" rather

> 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)
>       ;
>   }
> 

[PATCH v2] c++: fix ICE with -Wduplicated-cond [PR107593]

[Marek Polacek]

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.
> 
> 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
-- 
2.39.1

Re: [PATCH v2] c++: fix ICE with -Wduplicated-cond [PR107593]

[Jason Merrill]

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

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

[Marek Polacek]

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

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

[Jason Merrill]

On 1/30/23 21:34, Marek Polacek wrote:
> 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?

OK, thanks.

> -- >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