Add a note with a fixit in r309559. On 31 July 2017 at 10:50, Alex L <arpha...@gmail.com> wrote:
> That's an interesting case. I'll tweak the warning to diagnose this > scenario better today. > > On 29 July 2017 at 00:56, Hans Wennborg <h...@chromium.org> wrote: > >> On Fri, Jul 28, 2017 at 7:41 AM, Alex Lorenz via cfe-commits >> <cfe-commits@lists.llvm.org> wrote: >> > Author: arphaman >> > Date: Fri Jul 28 07:41:21 2017 >> > New Revision: 309386 >> > >> > URL: http://llvm.org/viewvc/llvm-project?rev=309386&view=rev >> > Log: >> > Recommit r308327 3rd time: Add a warning for missing >> > '#pragma pack (pop)' and suspicious uses of '#pragma pack' in included >> files >> > >> > The second recommit (r309106) was reverted because the "non-default >> #pragma >> > pack value chages the alignment of struct or union members in the >> included file" >> > warning proved to be too aggressive for external projects like Chromium >> > (https://bugs.chromium.org/p/chromium/issues/detail?id=749197). This >> recommit >> > makes the problematic warning a non-default one, and gives it the >> > -Wpragma-pack-suspicious-include warning option. >> > >> > 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 did get warnings with this version too, but this time it looks like >> a real bug :-) >> >> C:\b\c\builder\ClangToTWin_dll_\src\third_party\usrsctp\usrs >> ctplib\usrsctplib\netinet\sctp.h(51,9): >> error: unterminated '#pragma pack (push, ...)' at end of file >> [-Werror,-Wpragma-pack] >> >> The interesting thing is that the file does reset the alignment, but >> it does it with a "#pragma pack()" which doesn't pop the stack, but >> just resets to the default value. >> >> It might be worth tweaking the warning to give a better message for >> this. A "#pragma pack(push, ..)" followed by "#pragma pack()" seems >> pretty dodgy since there's no point in pushing if the code isn't going >> to pop. >> > >
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