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

  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


base-commit: 94673a121cfc7f9d51c9d05e31795477f4dc8dc7
  

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
> 
>
  

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
>>
>>
>
  

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
  

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)
      ;
  }
  

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)
>       ;
>   }
>