r309106 - Recommit r308327 2nd time: Add a warning for missing

[Hans Wennborg via cfe-commits]

On Wed, Jul 26, 2017 at 5:20 AM, Alex Lorenz via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: arphaman
> Date: Wed Jul 26 05:20:57 2017
> New Revision: 309106
>
> URL: http://llvm.org/viewvc/llvm-project?rev=309106&view=rev
> Log:
> Recommit r308327 2nd time: Add a warning for missing
> '#pragma pack (pop)' and suspicious uses of '#pragma pack' in included files
>
> The first recommit (r308441) caused a "non-default #pragma pack value might
> change the alignment of struct or union members in the included file" warning
> in LLVM itself. This recommit tweaks the added warning to avoid warnings for
> #includes that don't have any records that are affected by the non-default
> alignment. This tweak avoids the previously emitted warning in LLVM.
>
> Original message:
>
> This commit adds a new -Wpragma-pack warning. It warns in the following cases:
>
> - When a translation unit is missing terminating #pragma pack (pop) directives.
> - When entering an included file if the current alignment value as determined
>   by '#pragma pack' directives is different from the default alignment value.
> - When leaving an included file that changed the state of the current alignment
>   value.
>
> rdar://10184173
>
> Differential Revision: https://reviews.llvm.org/D35484

We have code in Chromium that does exactly this:

gles2_cmd_format.h does #pragma pack(push, 4) and then #includes a
file with some generated structs, with the intention that the pragma
applies to them.

What's the best way to pacify the warning in this case?

(We're tracking this in
https://bugs.chromium.org/p/chromium/issues/detail?id=749197)

Thanks,
Hans