[C] Warn if inline attributes conflict (PR c/18079)

On Thu, Mar 20, 2014 at 12:10:35PM +0100, Richard Biener wrote:
> On Thu, Mar 20, 2014 at 12:07 PM, Marek Polacek <polacek@redhat.com> wrote:
> > We should warn if someone wants to use both always_inline and noinline
> > attributes.
> >
> > Regtested/bootstrapped on x86_64-linux.  This is hardly 4.9 material,
> > so ok for 5.0?
> 
> Shouldn't the warning state that the attribute will be ignored?  That is,
> the common warning is
> 
>       warning (OPT_Wattributes, "%qE attribute ignored", name);
> 
> which could be amended with " due to conflict with ....".

Dunno.  I did what we do wrt conflicting cold/hot attributes.  But
here's a patch with what you suggest (with some Extra Quotes).

2014-03-20  Marek Polacek  <polacek@redhat.com>

	PR c/18079
c-family/
	* c-common.c (handle_noinline_attribute): Warn if the attribute
	conflicts with always_inline attribute.
	(handle_always_inline_attribute): Warn if the attribute conflicts
	with noinline attribute.
testsuite/
	* gcc.dg/pr18079.c: New test.


	Marek

On Thu, Mar 20, 2014 at 12:45 PM, Marek Polacek <polacek@redhat.com> wrote:
> On Thu, Mar 20, 2014 at 12:10:35PM +0100, Richard Biener wrote:
>> On Thu, Mar 20, 2014 at 12:07 PM, Marek Polacek <polacek@redhat.com> wrote:
>> > We should warn if someone wants to use both always_inline and noinline
>> > attributes.
>> >
>> > Regtested/bootstrapped on x86_64-linux.  This is hardly 4.9 material,
>> > so ok for 5.0?
>>
>> Shouldn't the warning state that the attribute will be ignored?  That is,
>> the common warning is
>>
>>       warning (OPT_Wattributes, "%qE attribute ignored", name);
>>
>> which could be amended with " due to conflict with ....".
>
> Dunno.  I did what we do wrt conflicting cold/hot attributes.  But
> here's a patch with what you suggest (with some Extra Quotes).

That works for me, please let Joseph some time to comment.

The "%qE attribute conflicts with attribute %s" way leaves me out in
the dark on what attribute will be in effect for the decl - it could be
either or none as far as I read it.  Or even both, with unspecified
behavior.

Richard.

> 2014-03-20  Marek Polacek  <polacek@redhat.com>
>
>         PR c/18079
> c-family/
>         * c-common.c (handle_noinline_attribute): Warn if the attribute
>         conflicts with always_inline attribute.
>         (handle_always_inline_attribute): Warn if the attribute conflicts
>         with noinline attribute.
> testsuite/
>         * gcc.dg/pr18079.c: New test.
>
> diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
> index abd96fb..5258e52 100644
> --- gcc/c-family/c-common.c
> +++ gcc/c-family/c-common.c
> @@ -6666,7 +6666,16 @@ handle_noinline_attribute (tree *node, tree name,
>                            int ARG_UNUSED (flags), bool *no_add_attrs)
>  {
>    if (TREE_CODE (*node) == FUNCTION_DECL)
> -    DECL_UNINLINABLE (*node) = 1;
> +    {
> +      if (lookup_attribute ("always_inline", DECL_ATTRIBUTES (*node)))
> +       {
> +         warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
> +                  "with %<always_inline%> attribute", name);
> +         *no_add_attrs = true;
> +       }
> +      else
> +       DECL_UNINLINABLE (*node) = 1;
> +    }
>    else
>      {
>        warning (OPT_Wattributes, "%qE attribute ignored", name);
> @@ -6704,9 +6713,16 @@ handle_always_inline_attribute (tree *node, tree name,
>  {
>    if (TREE_CODE (*node) == FUNCTION_DECL)
>      {
> -      /* Set the attribute and mark it for disregarding inline
> -        limits.  */
> -      DECL_DISREGARD_INLINE_LIMITS (*node) = 1;
> +      if (lookup_attribute ("noinline", DECL_ATTRIBUTES (*node)))
> +       {
> +         warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
> +                  "with %<noinline%> attribute", name);
> +         *no_add_attrs = true;
> +       }
> +      else
> +       /* Set the attribute and mark it for disregarding inline
> +          limits.  */
> +       DECL_DISREGARD_INLINE_LIMITS (*node) = 1;
>      }
>    else
>      {
> diff --git gcc/testsuite/gcc.dg/pr18079.c gcc/testsuite/gcc.dg/pr18079.c
> index e69de29..b84cdeb 100644
> --- gcc/testsuite/gcc.dg/pr18079.c
> +++ gcc/testsuite/gcc.dg/pr18079.c
> @@ -0,0 +1,33 @@
> +/* PR c/18079 */
> +/* { dg-do compile } */
> +/* { dg-options "-Wall" } */
> +
> +__attribute__ ((noinline))
> +__attribute__ ((always_inline))
> +int
> +fn1 (int r)
> +{ /* { dg-warning "attribute ignored due to conflict" } */
> +  return r & 4;
> +}
> +
> +__attribute__ ((noinline, always_inline))
> +int
> +fn2 (int r)
> +{ /* { dg-warning "attribute ignored due to conflict" } */
> +  return r & 4;
> +}
> +
> +__attribute__ ((always_inline))
> +__attribute__ ((noinline))
> +inline int
> +fn3 (int r)
> +{ /* { dg-warning "attribute ignored due to conflict" } */
> +  return r & 8;
> +}
> +
> +__attribute__ ((always_inline, noinline))
> +inline int
> +fn4 (int r)
> +{ /* { dg-warning "attribute ignored due to conflict" } */
> +  return r & 8;
> +}
>
>         Marek

On Thu, 20 Mar 2014, Marek Polacek wrote:

> Dunno.  I did what we do wrt conflicting cold/hot attributes.  But
> here's a patch with what you suggest (with some Extra Quotes).
> 
> 2014-03-20  Marek Polacek  <polacek@redhat.com>
> 
> 	PR c/18079
> c-family/
> 	* c-common.c (handle_noinline_attribute): Warn if the attribute
> 	conflicts with always_inline attribute.
> 	(handle_always_inline_attribute): Warn if the attribute conflicts
> 	with noinline attribute.
> testsuite/
> 	* gcc.dg/pr18079.c: New test.

This version is OK (for after 4.9 branches).

What happens if there are two declarations of the function, one with each 
attribute?  The testcase doesn't cover that.