On Tue, Jun 6, 2017 at 9:10 AM, Martin Sebor <mse...@gmail.com> wrote: > On 06/06/2017 10:07 AM, Martin Sebor wrote: >> >> On 06/05/2017 11:45 AM, H.J. Lu wrote: >>> >>> On Mon, Jun 5, 2017 at 8:11 AM, Joseph Myers <jos...@codesourcery.com> >>> wrote: >>>> >>>> The new attribute needs documentation. Should the test be in >>>> c-c++-common >>> >>> >>> This feature does support C++. But C++ compiler issues a slightly >>> different warning at a different location. >>> >>>> or does this feature not support C++? >>>> >>> >>> Here is the updated patch with documentation and a C++ test. This >>> patch caused a few testsuite failures: >>> >>> FAIL: gcc.dg/compat/struct-align-1 c_compat_x_tst.o compile >>> >>> >>> /export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.dg/compat//struct-align-1.h:169:1: >>> >>> warning: alignment 1 of 'struct B2_m_inner_p_outer' is less than 16 >>> >>> FAIL: g++.dg/torture/pr80334.C -O0 (test for excess errors) >>> >>> >>> /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/torture/pr80334.C:4:8: >>> >>> warning: alignment 1 of 'B' is less than 16 >>> >> >> Users often want the ability to control a warning, even when it >> certainly indicates a bug. I would suggest to add an option to >> make it possible for this warning as well. >> >> Btw., a bug related to some of those this warning is meant to >> detect is assigning the address of an underaligned object to >> a pointer of a natively aligned type. Clang has an option >> to detect this problem: -Waddress-of-packed-member. It might >> make a nice follow-on enhancement to add support for the same >> thing. I mention this because I think it would make sense to >> consider this when choosing the name of the GCC option (i.e., >> rather than having two distinct but closely related warnings, >> have one that detects both of these alignment type of bugs. > > > A bug that has some additional context on this is pr 51628. > A possible name for the new option suggested there is -Wpacked. > > Martin
Isn't -Waddress-of-packed-member a subset of or the same as -Wpacked? -- H.J.
