[PATCH] Fix -Wattribute-alias option

[PATCH] Fix -Wattribute-alias option

[Bernd Edlinger]

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Hi,

the command line option -Wattribute-alias (w/o the "=1") is currently broken,
and only -Wno-attribute-alias is still working, but what is worse, is that
the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
as it used to do in gcc-8, which breaks the linux warning suppression macro
because it relies on a _Pragma to work.

Fixed by declaring -Wattribute-alias as an alias to -Wattribute-alias=1
and the negated form as an alias to -Wattribute-alias=0.

Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
Is it OK for trunk?

Additionally I looked into the linux 4.20 build, got a couple "-Wmissing-attributes"
which seem easy to fix (by adding the cold attribute) and quite a lot
"-Waddress-of-packed-member" warnings, which I don't know how to fix properly.


Thanks
Bernd.

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2019-01-19  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* common.opt (-Wattribute-alias): Remove "no-" from name.
	Make -Wattribute-alias command line option and
	#pragma GCC diagnostic ignore "-Wattribute-alias" work again.

testsuite:
2019-01-19  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* gcc.dg/Wattribute-alias.c: Add test for #pragma GCC diagnostic ignore
	"-Wattribute-alias".

Index: gcc/common.opt
===================================================================
--- gcc/common.opt	(revision 268084)
+++ gcc/common.opt	(working copy)
@@ -550,14 +550,14 @@ Wattributes
 Common Var(warn_attributes) Init(1) Warning
 Warn about inappropriate attribute usage.
 
+Wattribute-alias
+Common Alias(Wattribute_alias=, 1, 0) Warning
+Warn about type safety and similar errors and mismatches in attribute alias and related.
+
 Wattribute-alias=
 Common Joined RejectNegative UInteger Var(warn_attribute_alias) Init(1) Warning IntegerRange(0, 2)
 Warn about type safety and similar errors and mismatches in attribute alias and related.
 
-Wno-attribute-alias
-Common Alias(Wattribute_alias=, 0, 0) Warning
-Disable -Wattribute-alias.
-
 Wcannot-profile
 Common Var(warn_cannot_profile) Init(1) Warning
 Warn when profiling instrumentation was requested, but could not be applied to
Index: gcc/testsuite/gcc.dg/Wattribute-alias.c
===================================================================
--- gcc/testsuite/gcc.dg/Wattribute-alias.c	(revision 268084)
+++ gcc/testsuite/gcc.dg/Wattribute-alias.c	(working copy)
@@ -14,6 +14,13 @@ ATTR (alias ("target_no_nothrow"), nothrow) void
 alias_nothrow (void);           /* { dg-warning ".alias_nothrow. specifies more restrictive attribute than its target .target_no_nothrow.: .nothrow." } */
 
 
+#pragma GCC diagnostic push "-Wattribute-alias"
+#pragma GCC diagnostic ignored "-Wattribute-alias"
+ATTR (alias ("target_no_nothrow"), nothrow) void
+alias_nothrow_ignored (void);
+#pragma GCC diagnostic pop "-Wattribute-alias"
+
+
 ATTR (pure) int
 alias_pure (void);
 

Re: [PATCH] Fix -Wattribute-alias option

[Arnd Bergmann]

On Sat, Jan 19, 2019 at 11:06 AM Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
>
> Hi,
>
> the command line option -Wattribute-alias (w/o the "=1") is currently broken,
> and only -Wno-attribute-alias is still working, but what is worse, is that
> the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
> as it used to do in gcc-8, which breaks the linux warning suppression macro
> because it relies on a _Pragma to work.

I'm surprised by this, since I have not seen the warning in a while. I am
however still using gcc-8.1 locally. Did this change later during the
gcc-8 branch?

     Arnd

Re: [PATCH] Fix -Wattribute-alias option

[Bernd Edlinger]

On 1/21/19 4:42 PM, Arnd Bergmann wrote:
> On Sat, Jan 19, 2019 at 11:06 AM Bernd Edlinger
> <bernd.edlinger@hotmail.de> wrote:
>>
>> Hi,
>>
>> the command line option -Wattribute-alias (w/o the "=1") is currently broken,
>> and only -Wno-attribute-alias is still working, but what is worse, is that
>> the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
>> as it used to do in gcc-8, which breaks the linux warning suppression macro
>> because it relies on a _Pragma to work.
> 
> I'm surprised by this, since I have not seen the warning in a while. I am
> however still using gcc-8.1 locally. Did this change later during the
> gcc-8 branch?
> 

Yes.

The -Wattribute-alias was split up in -Wattribute-alias=1 an -Wattribute-alias=2
and -Wmissing-attributes on gcc-trunk (but not in the gcc-8 branch as far as I know).

The -Wmissing-attribute also triggers in include/linux/module.h but for that one,
I will probably have to send a patch to the linux-kernel list.


$ svn log -r265980
------------------------------------------------------------------------
r265980 | msebor | 2018-11-09 18:32:52 +0100 (Fri, 09 Nov 2018) | 39 lines

PR middle-end/81824 - Warn for missing attributes with function aliases

gcc/c-family/ChangeLog:

	PR middle-end/81824
	* c-attribs.c (handle_copy_attribute): New function.

gcc/cp/ChangeLog:

	PR middle-end/81824
	* pt.c (warn_spec_missing_attributes): Move code to attribs.c.
	Call decls_mismatched_attributes.

gcc/ChangeLog:

	PR middle-end/81824
	* attribs.c (has_attribute): New helper function.
	(decls_mismatched_attributes, maybe_diag_alias_attributes): Same.
	* attribs.h (decls_mismatched_attributes): Declare.
	* cgraphunit.c (handle_alias_pairs): Call maybe_diag_alias_attributes.
	(maybe_diag_incompatible_alias): Use OPT_Wattribute_alias_.
	* common.opt (-Wattribute-alias): Take an argument.
	(-Wno-attribute-alias): New option.
	* doc/extend.texi (Common Function Attributes): Document copy.
	(Common Variable Attributes): Same.
	* doc/invoke.texi (-Wmissing-attributes): Document enhancement.
	(-Wattribute-alias): Document new option argument.

gcc/testsuite/ChangeLog:

	PR middle-end/81824
	* gcc.dg/Wattribute-alias.c: New test.
	* gcc.dg/Wmissing-attributes.c: New test.
	* gcc.dg/attr-copy.c: New test.
	* gcc.dg/attr-copy-2.c: New test.
	* gcc.dg/attr-copy-3.c: New test.
	* gcc.dg/attr-copy-4.c: New test.



Bernd.

Re: [PATCH] Fix -Wattribute-alias option

[Arnd Bergmann]

On Mon, Jan 21, 2019 at 4:55 PM Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
> On 1/21/19 4:42 PM, Arnd Bergmann wrote:
> > On Sat, Jan 19, 2019 at 11:06 AM Bernd Edlinger
> > <bernd.edlinger@hotmail.de> wrote:
> >>
> >> Hi,
> >>
> >> the command line option -Wattribute-alias (w/o the "=1") is currently broken,
> >> and only -Wno-attribute-alias is still working, but what is worse, is that
> >> the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
> >> as it used to do in gcc-8, which breaks the linux warning suppression macro
> >> because it relies on a _Pragma to work.
> >
> > I'm surprised by this, since I have not seen the warning in a while. I am
> > however still using gcc-8.1 locally. Did this change later during the
> > gcc-8 branch?
> >
>
> Yes.
>
> The -Wattribute-alias was split up in -Wattribute-alias=1 an -Wattribute-alias=2
> and -Wmissing-attributes on gcc-trunk (but not in the gcc-8 branch as far as I know).
>
> The -Wmissing-attribute also triggers in include/linux/module.h but for that one,
> I will probably have to send a patch to the linux-kernel list.

I got it, I misread your earlier message as saying that it also
happened on gcc-8.

     Arnd

Re: [PATCH] Fix -Wattribute-alias option

[Martin Sebor]

On 1/21/19 8:55 AM, Bernd Edlinger wrote:
> 
> 
> On 1/21/19 4:42 PM, Arnd Bergmann wrote:
>> On Sat, Jan 19, 2019 at 11:06 AM Bernd Edlinger
>> <bernd.edlinger@hotmail.de> wrote:
>>>
>>> Hi,
>>>
>>> the command line option -Wattribute-alias (w/o the "=1") is currently broken,
>>> and only -Wno-attribute-alias is still working, but what is worse, is that
>>> the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
>>> as it used to do in gcc-8, which breaks the linux warning suppression macro
>>> because it relies on a _Pragma to work.
>>
>> I'm surprised by this, since I have not seen the warning in a while. I am
>> however still using gcc-8.1 locally. Did this change later during the
>> gcc-8 branch?
>>
> 
> Yes.
> 
> The -Wattribute-alias was split up in -Wattribute-alias=1 an -Wattribute-alias=2
> and -Wmissing-attributes on gcc-trunk (but not in the gcc-8 branch as far as I know).
> 
> The -Wmissing-attribute also triggers in include/linux/module.h but for that one,
> I will probably have to send a patch to the linux-kernel list.

Miguel Ojeda has been working with me on the kernel changes.

Martin

> 
> 
> $ svn log -r265980
> ------------------------------------------------------------------------
> r265980 | msebor | 2018-11-09 18:32:52 +0100 (Fri, 09 Nov 2018) | 39 lines
> 
> PR middle-end/81824 - Warn for missing attributes with function aliases
> 
> gcc/c-family/ChangeLog:
> 
> 	PR middle-end/81824
> 	* c-attribs.c (handle_copy_attribute): New function.
> 
> gcc/cp/ChangeLog:
> 
> 	PR middle-end/81824
> 	* pt.c (warn_spec_missing_attributes): Move code to attribs.c.
> 	Call decls_mismatched_attributes.
> 
> gcc/ChangeLog:
> 
> 	PR middle-end/81824
> 	* attribs.c (has_attribute): New helper function.
> 	(decls_mismatched_attributes, maybe_diag_alias_attributes): Same.
> 	* attribs.h (decls_mismatched_attributes): Declare.
> 	* cgraphunit.c (handle_alias_pairs): Call maybe_diag_alias_attributes.
> 	(maybe_diag_incompatible_alias): Use OPT_Wattribute_alias_.
> 	* common.opt (-Wattribute-alias): Take an argument.
> 	(-Wno-attribute-alias): New option.
> 	* doc/extend.texi (Common Function Attributes): Document copy.
> 	(Common Variable Attributes): Same.
> 	* doc/invoke.texi (-Wmissing-attributes): Document enhancement.
> 	(-Wattribute-alias): Document new option argument.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR middle-end/81824
> 	* gcc.dg/Wattribute-alias.c: New test.
> 	* gcc.dg/Wmissing-attributes.c: New test.
> 	* gcc.dg/attr-copy.c: New test.
> 	* gcc.dg/attr-copy-2.c: New test.
> 	* gcc.dg/attr-copy-3.c: New test.
> 	* gcc.dg/attr-copy-4.c: New test.
> 
> 
> 
> Bernd.
> 

[PING] [PATCH] Fix -Wattribute-alias option

[Bernd Edlinger]

Hi,

I'd like to ping for this patch: https://gcc.gnu.org/ml/gcc-patches/2019-01/msg01120.html

This patch would be needed to avoid a rather ugly workaround for the the issue
in the linux-tree.


Thanks
Bernd.

On 1/19/19 11:06 AM, Bernd Edlinger wrote:
> Hi,
> 
> the command line option -Wattribute-alias (w/o the "=1") is currently broken,
> and only -Wno-attribute-alias is still working, but what is worse, is that
> the #pragma GCC diagnostic fails to recognize the string "-Wattribute-alias",
> as it used to do in gcc-8, which breaks the linux warning suppression macro
> because it relies on a _Pragma to work.
> 
> Fixed by declaring -Wattribute-alias as an alias to -Wattribute-alias=1
> and the negated form as an alias to -Wattribute-alias=0.
> 
> Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
> Is it OK for trunk?
> 
> Additionally I looked into the linux 4.20 build, got a couple "-Wmissing-attributes"
> which seem easy to fix (by adding the cold attribute) and quite a lot
> "-Waddress-of-packed-member" warnings, which I don't know how to fix properly.
> 
> 
> Thanks
> Bernd.
> 

Re: [PATCH] Fix -Wattribute-alias option

[Jakub Jelinek]

On Sat, Jan 19, 2019 at 10:06:29AM +0000, Bernd Edlinger wrote:
> 2019-01-19  Bernd Edlinger  <bernd.edlinger@hotmail.de>
> 
> 	* common.opt (-Wattribute-alias): Remove "no-" from name.
> 	Make -Wattribute-alias command line option and
> 	#pragma GCC diagnostic ignore "-Wattribute-alias" work again.
> 
> testsuite:
> 2019-01-19  Bernd Edlinger  <bernd.edlinger@hotmail.de>
> 
> 	* gcc.dg/Wattribute-alias.c: Add test for #pragma GCC diagnostic ignore
> 	"-Wattribute-alias".

Ok, thanks.

	Jakub