On Fri, 16 Jun 2017, H.J. Lu wrote:
> +@code{warning: alignment 8 of 'struct foo' is less than 16}.
I think @samp is better than @code for warnings, throughout, since they
aren't pieces of program code.
> +This warning can be disabled by @option{-Wno-if-not-aligned}.
> +The @code{warn_if_not_aligned } attribute can also be used for types
Stray space before }.
> +static void
> +handle_warn_if_not_align (tree field, unsigned int record_align)
Missing comment above this function explaining its semantics and those of
its arguments.
> + if ((record_align % warn_if_not_align) != 0)
> + warning (opt_w, "alignment %d of %qT is less than %d",
> + record_align, context, warn_if_not_align);
I'd expect %u for unsigned int alignments, instead of %d.
> + unsigned int off
> + = (tree_to_uhwi (DECL_FIELD_OFFSET (field))
> + + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)) / BITS_PER_UNIT);
> + if ((off % warn_if_not_align) != 0)
> + warning (opt_w, "%q+D offset %d in %qT isn't aligned to %d",
> + field, off, context, warn_if_not_align);
And you can have struct offsets that don't fit in unsigned int (i.e.
structures over 4 GB), so should be using unsigned HOST_WIDE_INT to store
the offset and %wu to print it. (Whereas various places in GCC restrict
alignments to unsigned int.)
What happens if you specify the attribute on a bit-field, or on a type
used to declare a bit-field? I don't think either of those particularly
makes sense, but I don't see tests for it either.
--
Joseph S. Myers
[email protected]
