c++: Small tweak to can_convert_eh [PR81660]

While messing with check_handlers_1, I spotted this bug report which
complains that we don't warn about the case when we have two duplicated
handlers of type int.  can_convert_eh implements [except.handle] and
that says: A handler is a match for an exception object of type E if
 - The handler is of type cv T or cv T& and E and T are the same type
   (ignoring the top-level cv-qualifiers), or [...]

but we don't implement this bullet properly for non-class types.  The
fix therefore seems pretty obvious.  Also change the return type to
bool when we're only returning yes/no.

gcc/cp/ChangeLog:

	PR c++/81660
	* except.c (can_convert_eh): Change the return type to bool.  If
	the type TO and FROM are the same, return true.

gcc/testsuite/ChangeLog:

	PR c++/81660
	* g++.dg/warn/Wexceptions3.C: New test.
	* g++.dg/eh/pr42859.C: Add dg-warning.
	* g++.dg/torture/pr81659.C: Likewise.
---
 gcc/cp/except.c                          | 14 +++++++-----
 gcc/testsuite/g++.dg/eh/pr42859.C        |  2 +-
 gcc/testsuite/g++.dg/torture/pr81659.C   |  2 +-
 gcc/testsuite/g++.dg/warn/Wexceptions3.C | 29 ++++++++++++++++++++++++
 4 files changed, 39 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions3.C


base-commit: f72af3af8d526793e4927daf44ae0611c3d0cc85

On 11/6/20 1:15 AM, Marek Polacek wrote:
> While messing with check_handlers_1, I spotted this bug report which
> complains that we don't warn about the case when we have two duplicated
> handlers of type int.  can_convert_eh implements [except.handle] and
> that says: A handler is a match for an exception object of type E if
>   - The handler is of type cv T or cv T& and E and T are the same type
>     (ignoring the top-level cv-qualifiers), or [...]
> 
> but we don't implement this bullet properly for non-class types.  The
> fix therefore seems pretty obvious.  Also change the return type to
> bool when we're only returning yes/no.

OK.

> gcc/cp/ChangeLog:
> 
> 	PR c++/81660
> 	* except.c (can_convert_eh): Change the return type to bool.  If
> 	the type TO and FROM are the same, return true.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/81660
> 	* g++.dg/warn/Wexceptions3.C: New test.
> 	* g++.dg/eh/pr42859.C: Add dg-warning.
> 	* g++.dg/torture/pr81659.C: Likewise.
> ---
>   gcc/cp/except.c                          | 14 +++++++-----
>   gcc/testsuite/g++.dg/eh/pr42859.C        |  2 +-
>   gcc/testsuite/g++.dg/torture/pr81659.C   |  2 +-
>   gcc/testsuite/g++.dg/warn/Wexceptions3.C | 29 ++++++++++++++++++++++++
>   4 files changed, 39 insertions(+), 8 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions3.C
> 
> diff --git a/gcc/cp/except.c b/gcc/cp/except.c
> index b72a28c1aa9..0f6c76b9892 100644
> --- a/gcc/cp/except.c
> +++ b/gcc/cp/except.c
> @@ -41,7 +41,6 @@ static tree do_allocate_exception (tree);
>   static tree wrap_cleanups_r (tree *, int *, void *);
>   static int complete_ptr_ref_or_void_ptr_p (tree, tree);
>   static bool is_admissible_throw_operand_or_catch_parameter (tree, bool);
> -static int can_convert_eh (tree, tree);
>   
>   /* Sets up all the global eh stuff that needs to be initialized at the
>      start of compilation.  */
> @@ -932,31 +931,34 @@ nothrow_libfn_p (const_tree fn)
>   /* Returns nonzero if an exception of type FROM will be caught by a
>      handler for type TO, as per [except.handle].  */
>   
> -static int
> +static bool
>   can_convert_eh (tree to, tree from)
>   {
>     to = non_reference (to);
>     from = non_reference (from);
>   
> +  if (same_type_ignoring_top_level_qualifiers_p (to, from))
> +    return true;
> +
>     if (TYPE_PTR_P (to) && TYPE_PTR_P (from))
>       {
>         to = TREE_TYPE (to);
>         from = TREE_TYPE (from);
>   
>         if (! at_least_as_qualified_p (to, from))
> -	return 0;
> +	return false;
>   
>         if (VOID_TYPE_P (to))
> -	return 1;
> +	return true;
>   
>         /* Else fall through.  */
>       }
>   
>     if (CLASS_TYPE_P (to) && CLASS_TYPE_P (from)
>         && publicly_uniquely_derived_p (to, from))
> -    return 1;
> +    return true;
>   
> -  return 0;
> +  return false;
>   }
>   
>   /* Check whether any of the handlers in I are shadowed by another handler
> diff --git a/gcc/testsuite/g++.dg/eh/pr42859.C b/gcc/testsuite/g++.dg/eh/pr42859.C
> index a9f1473bc85..0de91409c83 100644
> --- a/gcc/testsuite/g++.dg/eh/pr42859.C
> +++ b/gcc/testsuite/g++.dg/eh/pr42859.C
> @@ -13,7 +13,7 @@ ptw32_terminate (void)
>       catch (int)
>       {
>       }
> -    catch (int)
> +    catch (int) // { dg-warning "will be caught by earlier handler" }
>       {
>       }
>     }
> diff --git a/gcc/testsuite/g++.dg/torture/pr81659.C b/gcc/testsuite/g++.dg/torture/pr81659.C
> index 3696957532e..074099be6fc 100644
> --- a/gcc/testsuite/g++.dg/torture/pr81659.C
> +++ b/gcc/testsuite/g++.dg/torture/pr81659.C
> @@ -12,7 +12,7 @@ a (int b)
>     catch (int)
>       {
>       }
> -  catch (int)
> +  catch (int) // { dg-warning "will be caught by earlier handler" }
>       {
>       }
>   }
> diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions3.C b/gcc/testsuite/g++.dg/warn/Wexceptions3.C
> new file mode 100644
> index 00000000000..97fda9dbd91
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wexceptions3.C
> @@ -0,0 +1,29 @@
> +// PR c++/81660
> +
> +void bar (int);
> +
> +void
> +fn (int b)
> +{
> +  if (b)
> +    throw;
> +  try
> +    {
> +      bar (3);
> +    }
> +  catch (int)
> +    {
> +    }
> +  catch (int) // { dg-warning "will be caught by earlier handler" }
> +    {
> +    }
> +  catch (const int) // { dg-warning "will be caught by earlier handler" }
> +    {
> +    }
> +  catch (int &) // { dg-warning "will be caught by earlier handler" }
> +    {
> +    }
> +  catch (const int &) // { dg-warning "will be caught by earlier handler" }
> +    {
> +    }
> +}
> 
> base-commit: f72af3af8d526793e4927daf44ae0611c3d0cc85
>