[PATCH] c++: Add -Wexceptions warning option [PR97675]

[PATCH] c++: Add -Wexceptions warning option [PR97675]

[Marek Polacek]

This PR asks that we add a warning option for an existing (very old)
warning, so that it can be disabled selectively.  clang++ uses
-Wexceptions for this, so I added this new option rather than using
e.g. -Wnoexcept.

gcc/c-family/ChangeLog:

	PR c++/97675
	* c.opt (Wexceptions): New option.

gcc/cp/ChangeLog:

	PR c++/97675
	* except.c (check_handlers_1): Use OPT_Wexceptions for the
	warning.  Use inform for the second part of the warning.

gcc/ChangeLog:

	PR c++/97675
	* doc/invoke.texi: Document -Wexceptions.

gcc/testsuite/ChangeLog:

	PR c++/97675
	* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
	* g++.dg/warn/Wexceptions1.C: New test.
	* g++.dg/warn/Wexceptions2.C: New test.
---
 gcc/c-family/c.opt                          |  4 ++++
 gcc/cp/except.c                             |  9 ++++-----
 gcc/doc/invoke.texi                         |  8 +++++++-
 gcc/testsuite/g++.dg/warn/Wexceptions1.C    |  9 +++++++++
 gcc/testsuite/g++.dg/warn/Wexceptions2.C    | 10 ++++++++++
 gcc/testsuite/g++.old-deja/g++.eh/catch10.C |  4 ++--
 6 files changed, 36 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions1.C
 create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions2.C

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 426636be839..9493acb82ff 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -579,6 +579,10 @@ Werror-implicit-function-declaration
 C ObjC RejectNegative Warning Alias(Werror=, implicit-function-declaration)
 This switch is deprecated; use -Werror=implicit-function-declaration instead.
 
+Wexceptions
+C++ ObjC++ Var(warn_exceptions) Init(1)
+Warn when an exception handler is shadowed by another handler.
+
 Wextra
 C ObjC C++ ObjC++ Warning
 ; in common.opt
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index cb1a4105dae..985206f6a64 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -975,11 +975,10 @@ check_handlers_1 (tree master, tree_stmt_iterator i)
       tree handler = tsi_stmt (i);
       if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
 	{
-	  warning_at (EXPR_LOCATION (handler), 0,
-		      "exception of type %qT will be caught",
-		      TREE_TYPE (handler));
-	  warning_at (EXPR_LOCATION (master), 0,
-		      "   by earlier handler for %qT", type);
+	  if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
+			  "exception of type %qT will be caught by earlier "
+			  "handler", TREE_TYPE (handler)))
+	    inform (EXPR_LOCATION (master), "for type %qT", type);
 	  break;
 	}
     }
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5320e6c1e1e..4c6435d5e14 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -240,7 +240,7 @@ in the following sections.
 -Wctor-dtor-privacy  -Wno-delete-incomplete @gol
 -Wdelete-non-virtual-dtor  -Wdeprecated-copy  -Wdeprecated-copy-dtor @gol
 -Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
--Weffc++  -Wextra-semi  -Wno-inaccessible-base @gol
+-Weffc++  -Wno-exceptions -Wextra-semi  -Wno-inaccessible-base @gol
 -Wno-inherited-variadic-ctor  -Wno-init-list-lifetime @gol
 -Wno-invalid-offsetof  -Wno-literal-suffix  -Wmismatched-tags @gol
 -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing @gol
@@ -3738,6 +3738,12 @@ When selecting this option, be aware that the standard library
 headers do not obey all of these guidelines; use @samp{grep -v}
 to filter out those warnings.
 
+@item -Wno-exceptions @r{(C++ and Objective-C++ only)}
+@opindex Wexceptions
+@opindex Wno-exceptions
+Disable the warning about the case when an exception handler is shadowed by
+another handler, which can point out a wrong ordering of exception handlers.
+
 @item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
 @opindex Wstrict-null-sentinel
 @opindex Wno-strict-null-sentinel
diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions1.C b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
new file mode 100644
index 00000000000..af140fd0dc2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
@@ -0,0 +1,9 @@
+// PR c++/97675
+
+struct Base { };
+struct Child : Base { };
+int main() {
+    try { throw Child(); }
+    catch (Base const&) { }
+    catch (Child const&) { } // { dg-warning "exception of type .Child. will be caught by earlier handler" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions2.C b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
new file mode 100644
index 00000000000..07c5155ac06
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
@@ -0,0 +1,10 @@
+// PR c++/97675
+// { dg-additional-options -Wno-exceptions }
+
+struct Base { };
+struct Child : Base { };
+int main() {
+    try { throw Child(); }
+    catch (Base const&) { }
+    catch (Child const&) { } // { dg-bogus "exception of type .Child. will be caught by earlier handler" }
+}
diff --git a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
index 2300a946187..7cc609645a2 100644
--- a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
+++ b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
@@ -13,8 +13,8 @@ void g()
   catch (A*) { }
 
   try { f(); }
-  catch (A*) { }		// { dg-warning "" } A* before B*
-  catch (B*) { }		// { dg-warning "" } A* before B*
+  catch (A*) { }		// { dg-message "for type" } A* before B*
+  catch (B*) { }		// { dg-warning "will be caught" } A* before B*
 
   try { f(); }
   catch (A*) { }

base-commit: fab72592d86d11b89a01f0f3c2c9c329d43466c1
-- 
2.28.0

Re: [PATCH] c++: Add -Wexceptions warning option [PR97675]

[Jason Merrill]

On 11/5/20 11:03 AM, Marek Polacek wrote:
> This PR asks that we add a warning option for an existing (very old)
> warning, so that it can be disabled selectively.  clang++ uses
> -Wexceptions for this, so I added this new option rather than using
> e.g. -Wnoexcept.

OK.

> gcc/c-family/ChangeLog:
> 
> 	PR c++/97675
> 	* c.opt (Wexceptions): New option.
> 
> gcc/cp/ChangeLog:
> 
> 	PR c++/97675
> 	* except.c (check_handlers_1): Use OPT_Wexceptions for the
> 	warning.  Use inform for the second part of the warning.
> 
> gcc/ChangeLog:
> 
> 	PR c++/97675
> 	* doc/invoke.texi: Document -Wexceptions.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/97675
> 	* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
> 	* g++.dg/warn/Wexceptions1.C: New test.
> 	* g++.dg/warn/Wexceptions2.C: New test.
> ---
>   gcc/c-family/c.opt                          |  4 ++++
>   gcc/cp/except.c                             |  9 ++++-----
>   gcc/doc/invoke.texi                         |  8 +++++++-
>   gcc/testsuite/g++.dg/warn/Wexceptions1.C    |  9 +++++++++
>   gcc/testsuite/g++.dg/warn/Wexceptions2.C    | 10 ++++++++++
>   gcc/testsuite/g++.old-deja/g++.eh/catch10.C |  4 ++--
>   6 files changed, 36 insertions(+), 8 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions1.C
>   create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions2.C
> 
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index 426636be839..9493acb82ff 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -579,6 +579,10 @@ Werror-implicit-function-declaration
>   C ObjC RejectNegative Warning Alias(Werror=, implicit-function-declaration)
>   This switch is deprecated; use -Werror=implicit-function-declaration instead.
>   
> +Wexceptions
> +C++ ObjC++ Var(warn_exceptions) Init(1)
> +Warn when an exception handler is shadowed by another handler.
> +
>   Wextra
>   C ObjC C++ ObjC++ Warning
>   ; in common.opt
> diff --git a/gcc/cp/except.c b/gcc/cp/except.c
> index cb1a4105dae..985206f6a64 100644
> --- a/gcc/cp/except.c
> +++ b/gcc/cp/except.c
> @@ -975,11 +975,10 @@ check_handlers_1 (tree master, tree_stmt_iterator i)
>         tree handler = tsi_stmt (i);
>         if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
>   	{
> -	  warning_at (EXPR_LOCATION (handler), 0,
> -		      "exception of type %qT will be caught",
> -		      TREE_TYPE (handler));
> -	  warning_at (EXPR_LOCATION (master), 0,
> -		      "   by earlier handler for %qT", type);
> +	  if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
> +			  "exception of type %qT will be caught by earlier "
> +			  "handler", TREE_TYPE (handler)))
> +	    inform (EXPR_LOCATION (master), "for type %qT", type);
>   	  break;
>   	}
>       }
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 5320e6c1e1e..4c6435d5e14 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -240,7 +240,7 @@ in the following sections.
>   -Wctor-dtor-privacy  -Wno-delete-incomplete @gol
>   -Wdelete-non-virtual-dtor  -Wdeprecated-copy  -Wdeprecated-copy-dtor @gol
>   -Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
> --Weffc++  -Wextra-semi  -Wno-inaccessible-base @gol
> +-Weffc++  -Wno-exceptions -Wextra-semi  -Wno-inaccessible-base @gol
>   -Wno-inherited-variadic-ctor  -Wno-init-list-lifetime @gol
>   -Wno-invalid-offsetof  -Wno-literal-suffix  -Wmismatched-tags @gol
>   -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing @gol
> @@ -3738,6 +3738,12 @@ When selecting this option, be aware that the standard library
>   headers do not obey all of these guidelines; use @samp{grep -v}
>   to filter out those warnings.
>   
> +@item -Wno-exceptions @r{(C++ and Objective-C++ only)}
> +@opindex Wexceptions
> +@opindex Wno-exceptions
> +Disable the warning about the case when an exception handler is shadowed by
> +another handler, which can point out a wrong ordering of exception handlers.
> +
>   @item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
>   @opindex Wstrict-null-sentinel
>   @opindex Wno-strict-null-sentinel
> diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions1.C b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
> new file mode 100644
> index 00000000000..af140fd0dc2
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
> @@ -0,0 +1,9 @@
> +// PR c++/97675
> +
> +struct Base { };
> +struct Child : Base { };
> +int main() {
> +    try { throw Child(); }
> +    catch (Base const&) { }
> +    catch (Child const&) { } // { dg-warning "exception of type .Child. will be caught by earlier handler" }
> +}
> diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions2.C b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
> new file mode 100644
> index 00000000000..07c5155ac06
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
> @@ -0,0 +1,10 @@
> +// PR c++/97675
> +// { dg-additional-options -Wno-exceptions }
> +
> +struct Base { };
> +struct Child : Base { };
> +int main() {
> +    try { throw Child(); }
> +    catch (Base const&) { }
> +    catch (Child const&) { } // { dg-bogus "exception of type .Child. will be caught by earlier handler" }
> +}
> diff --git a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
> index 2300a946187..7cc609645a2 100644
> --- a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
> +++ b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
> @@ -13,8 +13,8 @@ void g()
>     catch (A*) { }
>   
>     try { f(); }
> -  catch (A*) { }		// { dg-warning "" } A* before B*
> -  catch (B*) { }		// { dg-warning "" } A* before B*
> +  catch (A*) { }		// { dg-message "for type" } A* before B*
> +  catch (B*) { }		// { dg-warning "will be caught" } A* before B*
>   
>     try { f(); }
>     catch (A*) { }
> 
> base-commit: fab72592d86d11b89a01f0f3c2c9c329d43466c1
> 

Re: [PATCH] c++: Add -Wexceptions warning option [PR97675]

[David Malcolm]

On Thu, 2020-11-05 at 11:03 -0500, Marek Polacek via Gcc-patches wrote:
> This PR asks that we add a warning option for an existing (very old)
> warning, so that it can be disabled selectively.  clang++ uses
> -Wexceptions for this, so I added this new option rather than using
> e.g. -Wnoexcept.
> 
> gcc/c-family/ChangeLog:
> 
> 	PR c++/97675
> 	* c.opt (Wexceptions): New option.
> 
> gcc/cp/ChangeLog:
> 
> 	PR c++/97675
> 	* except.c (check_handlers_1): Use OPT_Wexceptions for the
> 	warning.  Use inform for the second part of the warning.
> 
> gcc/ChangeLog:
> 
> 	PR c++/97675
> 	* doc/invoke.texi: Document -Wexceptions.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/97675
> 	* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
> 	* g++.dg/warn/Wexceptions1.C: New test.
> 	* g++.dg/warn/Wexceptions2.C: New test.
> ---
>  gcc/c-family/c.opt                          |  4 ++++
>  gcc/cp/except.c                             |  9 ++++-----
>  gcc/doc/invoke.texi                         |  8 +++++++-
>  gcc/testsuite/g++.dg/warn/Wexceptions1.C    |  9 +++++++++
>  gcc/testsuite/g++.dg/warn/Wexceptions2.C    | 10 ++++++++++
>  gcc/testsuite/g++.old-deja/g++.eh/catch10.C |  4 ++--
>  6 files changed, 36 insertions(+), 8 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions1.C
>  create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions2.C
> 
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index 426636be839..9493acb82ff 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -579,6 +579,10 @@ Werror-implicit-function-declaration
>  C ObjC RejectNegative Warning Alias(Werror=, implicit-function-
> declaration)
>  This switch is deprecated; use -Werror=implicit-function-declaration 
> instead.
>  
> +Wexceptions
> +C++ ObjC++ Var(warn_exceptions) Init(1)
> +Warn when an exception handler is shadowed by another handler.
> +
>  Wextra
>  C ObjC C++ ObjC++ Warning
>  ; in common.opt
> diff --git a/gcc/cp/except.c b/gcc/cp/except.c
> index cb1a4105dae..985206f6a64 100644
> --- a/gcc/cp/except.c
> +++ b/gcc/cp/except.c
> @@ -975,11 +975,10 @@ check_handlers_1 (tree master,
> tree_stmt_iterator i)
>        tree handler = tsi_stmt (i);
>        if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE
> (handler)))
>  	{

Can you add an auto_diagnostic_group here please.

> -	  warning_at (EXPR_LOCATION (handler), 0,
> -		      "exception of type %qT will be caught",
> -		      TREE_TYPE (handler));
> -	  warning_at (EXPR_LOCATION (master), 0,
> -		      "   by earlier handler for %qT", type);
> +	  if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
> +			  "exception of type %qT will be caught by
> earlier "
> +			  "handler", TREE_TYPE (handler)))
> +	    inform (EXPR_LOCATION (master), "for type %qT", type);
>  	  break;
>  	}
>      }

Thanks
Dave

Re: [PATCH] c++: Add -Wexceptions warning option [PR97675]

[Marek Polacek]

On Thu, Nov 05, 2020 at 06:13:41PM -0500, David Malcolm via Gcc-patches wrote:
> On Thu, 2020-11-05 at 11:03 -0500, Marek Polacek via Gcc-patches wrote:
> > This PR asks that we add a warning option for an existing (very old)
> > warning, so that it can be disabled selectively.  clang++ uses
> > -Wexceptions for this, so I added this new option rather than using
> > e.g. -Wnoexcept.
> > 
> > gcc/c-family/ChangeLog:
> > 
> > 	PR c++/97675
> > 	* c.opt (Wexceptions): New option.
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	PR c++/97675
> > 	* except.c (check_handlers_1): Use OPT_Wexceptions for the
> > 	warning.  Use inform for the second part of the warning.
> > 
> > gcc/ChangeLog:
> > 
> > 	PR c++/97675
> > 	* doc/invoke.texi: Document -Wexceptions.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	PR c++/97675
> > 	* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
> > 	* g++.dg/warn/Wexceptions1.C: New test.
> > 	* g++.dg/warn/Wexceptions2.C: New test.
> > ---
> >  gcc/c-family/c.opt                          |  4 ++++
> >  gcc/cp/except.c                             |  9 ++++-----
> >  gcc/doc/invoke.texi                         |  8 +++++++-
> >  gcc/testsuite/g++.dg/warn/Wexceptions1.C    |  9 +++++++++
> >  gcc/testsuite/g++.dg/warn/Wexceptions2.C    | 10 ++++++++++
> >  gcc/testsuite/g++.old-deja/g++.eh/catch10.C |  4 ++--
> >  6 files changed, 36 insertions(+), 8 deletions(-)
> >  create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions1.C
> >  create mode 100644 gcc/testsuite/g++.dg/warn/Wexceptions2.C
> > 
> > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> > index 426636be839..9493acb82ff 100644
> > --- a/gcc/c-family/c.opt
> > +++ b/gcc/c-family/c.opt
> > @@ -579,6 +579,10 @@ Werror-implicit-function-declaration
> >  C ObjC RejectNegative Warning Alias(Werror=, implicit-function-
> > declaration)
> >  This switch is deprecated; use -Werror=implicit-function-declaration 
> > instead.
> >  
> > +Wexceptions
> > +C++ ObjC++ Var(warn_exceptions) Init(1)
> > +Warn when an exception handler is shadowed by another handler.
> > +
> >  Wextra
> >  C ObjC C++ ObjC++ Warning
> >  ; in common.opt
> > diff --git a/gcc/cp/except.c b/gcc/cp/except.c
> > index cb1a4105dae..985206f6a64 100644
> > --- a/gcc/cp/except.c
> > +++ b/gcc/cp/except.c
> > @@ -975,11 +975,10 @@ check_handlers_1 (tree master,
> > tree_stmt_iterator i)
> >        tree handler = tsi_stmt (i);
> >        if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE
> > (handler)))
> >  	{
> 
> Can you add an auto_diagnostic_group here please.

Yup, I've pushed this:

From 44e1f63e20fec07e3a10d8e75336cfda64c911bf Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Thu, 5 Nov 2020 18:23:56 -0500
Subject: [pushed] c++: Add auto_diagnostic_group to check_handlers_1.

This was missing.

gcc/cp/ChangeLog:

	* except.c (check_handlers_1): Add auto_diagnostic_group.
---
 gcc/cp/except.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 985206f6a64..b72a28c1aa9 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -975,6 +975,7 @@ check_handlers_1 (tree master, tree_stmt_iterator i)
       tree handler = tsi_stmt (i);
       if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
 	{
+	  auto_diagnostic_group d;
 	  if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
 			  "exception of type %qT will be caught by earlier "
 			  "handler", TREE_TYPE (handler)))

base-commit: e6fd02cc6d874c523466250a1cb724e0c7af9d75
-- 
2.28.0