[PATCH] Fix pedanic warnings without a storage increase

[Joel Sherrill]

On Tue, Aug 30, 2022 at 9:40 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 30/08/2022 16:38, Joel Sherrill wrote:
> >     +  /*
> >     +   * Ignore these warnings:
> >     +   *
> >     +   * - invalid use of structure with flexible array member
> >     +   *
> >     +   * - struct has no members
> >     +   */
> >     +  #pragma GCC diagnostic push
> >     +  #pragma GCC diagnostic ignored "-Wpedantic"
> >
> >
> > This is heavy handed. -Warray-bounds should be enough.
>
> There is no array bounds warning. There are only the above two
> -Wpedantic warnings.
>

OK I was suggesting that because -Wzero-length-bounds which should be
the precise warning was turned on by -Warray-bounds.

How about just -Wzero-length-bounds?

-Wzero-length-bounds

Warn about accesses to elements of zero-length array members that might
overlap other members of the same object. Declaring interior zero-length
arrays is discouraged because accesses to them are undefined. See See Zero
Length
<https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Zero-Length.html#Zero-Length>
.

For example, the first two stores in function bad are diagnosed because the
array elements overlap the subsequent members b and c. The third store is
diagnosed by -Warray-bounds because it is beyond the bounds of the
enclosing object.

struct X { int a[0]; int b, c; };
struct X x;

void bad (void)
{
  x.a[0] = 0;   // -Wzero-length-bounds
  x.a[1] = 1;   // -Wzero-length-bounds
  x.a[2] = 2;   // -Warray-bounds
}

Option -Wzero-length-bounds is enabled by -Warray-bounds.


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