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| author | Richard Biener <rguenther@suse.de> | 2016-12-16 09:40:03 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2016-12-16 09:40:03 +0000 |
| commit | b7fc43d7c747d190e197ca89cfce4f1d9def7c7e (patch) | |
| tree | e7a4831ca7b46e08d1f5bc38c1d4f221aa7cfbbe /gcc/stor-layout.c | |
| parent | c4d5c5e6ac73cac2b89d039eff9874ff80742589 (diff) | |
| download | gcc-b7fc43d7c747d190e197ca89cfce4f1d9def7c7e.zip gcc-b7fc43d7c747d190e197ca89cfce4f1d9def7c7e.tar.gz gcc-b7fc43d7c747d190e197ca89cfce4f1d9def7c7e.tar.bz2 | |
re PR c++/71694 (store-data race with bitfields and tail-padding in C++)
2016-12-16 Richard Biener <rguenther@suse.de>
PR c++/71694
* langhooks-def.h (lhd_unit_size_without_reusable_padding): Declare.
(LANG_HOOKS_UNIT_SIZE_WITHOUT_REUSABLE_PADDING): Define.
(LANG_HOOKS_FOR_TYPES_INITIALIZER): Adjust.
* langhooks.h (struct lang_hooks_for_types): Add
unit_size_without_reusable_padding.
* langhooks.c (lhd_unit_size_without_reusable_padding): New.
* stor-layout.c (finish_bitfield_representative): Use
unit_size_without_reusable_padding langhook to decide on the
last representatives size.
cp/
* cp-objcp-common.h (cp_unit_size_without_reusable_padding): Declare.
(LANG_HOOKS_UNIT_SIZE_WITHOUT_REUSABLE_PADDING): Define.
* cp-objcp-common.c (cp_unit_size_without_reusable_padding): New.
* g++.dg/pr71694.C: New testcase.
From-SVN: r243738
Diffstat (limited to 'gcc/stor-layout.c')
| -rw-r--r-- | gcc/stor-layout.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c index 5a4bcf1..0aa3861 100644 --- a/gcc/stor-layout.c +++ b/gcc/stor-layout.c @@ -1864,13 +1864,14 @@ finish_bitfield_representative (tree repr, tree field) } else { - /* ??? If you consider that tail-padding of this struct might be - re-used when deriving from it we cannot really do the following - and thus need to set maxsize to bitsize? Also we cannot - generally rely on maxsize to fold to an integer constant, so - use bitsize as fallback for this case. */ - tree maxsize = size_diffop (TYPE_SIZE_UNIT (DECL_CONTEXT (field)), - DECL_FIELD_OFFSET (repr)); + /* Note that if the C++ FE sets up tail-padding to be re-used it + creates a as-base variant of the type with TYPE_SIZE adjusted + accordingly. So it is safe to include tail-padding here. */ + tree aggsize = lang_hooks.types.unit_size_without_reusable_padding + (DECL_CONTEXT (field)); + tree maxsize = size_diffop (aggsize, DECL_FIELD_OFFSET (repr)); + /* We cannot generally rely on maxsize to fold to an integer constant, + so use bitsize as fallback for this case. */ if (tree_fits_uhwi_p (maxsize)) maxbitsize = (tree_to_uhwi (maxsize) * BITS_PER_UNIT - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))); |