Summary:
We should avoid a tail padding not only if the last field
has zero size but also if the last field is a struct with a flexible array.
If/when http://reviews.llvm.org/D5478 is committed,
this will also handle the case of structs with zero-sized arrays.
Reviewers: majnemer, rsmith
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D5924
llvm-svn: 220708
Summary:
The general approach is to add extra paddings after every field
in AST/RecordLayoutBuilder.cpp, then add code to CTORs/DTORs that poisons the paddings
(CodeGen/CGClass.cpp).
Everything is done under the flag -fsanitize-address-field-padding.
The blacklist file (-fsanitize-blacklist) allows to avoid the transformation
for given classes or source files.
See also https://code.google.com/p/address-sanitizer/wiki/IntraObjectOverflow
Test Plan: run SPEC2006 and some of the Chromium tests with -fsanitize-address-field-padding
Reviewers: samsonov, rnk, rsmith
Reviewed By: rsmith
Subscribers: majnemer, cfe-commits
Differential Revision: http://reviews.llvm.org/D5687
llvm-svn: 219961
Empty records do not always have size equivalent to their alignment.
They only do so when their alignment is at least as large as the minimum
empty struct size: 1 byte in C++ and 4 bytes in C.
llvm-svn: 218661
Usually, overriding a virtual function defined in a virtual base
required emission of a vtordisp slot in the record. However no vtordisp
is needed if the overriding function is pure; it should be impossible to
observe the pure virtual method.
This fixes PR21046.
llvm-svn: 218340
The MS ABI has a notion of 'required alignment' for fields; this
alignment supercedes pragma pack directives.
MSVC takes into account alignment attributes on typedefs when
determining whether or not a field has a certain required alignment.
Do the same in clang by tracking whether or not we saw such an attribute
when calculating the type's bitwidth and alignment.
This fixes PR20418.
Reviewers: rnk
Differential Revision: http://reviews.llvm.org/D4714
llvm-svn: 214274
We would correctly insert sufficiently aligned padding between vbases
when our leading base was empty, however we would neglect to increase
the required alignment of the most derived class.
This fixes PR20315.
llvm-svn: 213123
No functionality changed, just some cleanups:
- Switch some loops to range-based for.
- Name some iterators with a more creative name than "I".
- Reduce dependence on auto. Does RD->bases() give you a list of
CXXBaseSpecifiers or CXXRecordDecls? It's more clear to just say which
upfront.
llvm-svn: 213121
Previously, it was believed that #pragma vtordisp(0) would prohibit the
generation of any and all vtordisps.
In actuality, it only disables the generation of additional vtordisps.
This fixes PR19413.
llvm-svn: 206124
A portion of the vtordisp computation that was previously unguarded by a
test for the declaration of user defined constructors/destructors was
erroniously adding vtordisps to things that shouldn't have them. This
patch correctly guards that codepath. In addition, it updates the
comments to make them more clear. Test case is included.
llvm-svn: 206077
This patch updates the comments in RecordLayoutBuilder about record
layout in the MS-ABI. Also, I added a section about known
incompatibilities.
llvm-svn: 206010
In version 9 (VS2010) (and prior)? versions of msvc, if the last field
in a record was a bitfield padding equal to the size of the storage
class of that bitfield was added before each vbase and vtordisp. This
patch removes that feature from clang and updates the lit tests to
reflect it.
llvm-svn: 206004
The vbptr is injected after the last non-virtual base lexographically
rather than the last non-virtual base in layout order. Test case
included. Also, some line ending fixes.
llvm-svn: 206000
When __declspec(align()) is applied to a bitfield it affects the
alignment rather than the required alignment of the struct. The major
feature that this patch adds is that the alignment of the structure
obeys the alignment of __declspec(align()) from the bitfield over the
value specified in pragma pack.
Test cases are included.
The patch also includes some small cleanups in recordlayoutbuilder and
some cleanups to some lit tests, including line endings (but no
functionality change to lit tests)
llvm-svn: 205994
This patch changes how we determine if padding is needed between two
bases in msvc compatibility mode. Test cases included.
In addition, a very minor change to the printing of structures to ease
lit testing.
llvm-svn: 205933
As of cl.exe version 18, the special layout rules for structs with
alignment 16 or greater has been dropped. This patch drops the behavior
from clang. This patch also updates the lit tests to reflect the
change.
llvm-svn: 204674
or virtual functions, but permit that error to be downgraded to
a warning (with -Wno-error=incompatible-ms-struct), and officially
support this kind of dual, ABI-mixing layout.
The basic problem here is that projects which use ms_struct are often
not very circumspect about what types they annotate; for example,
some projects enable the pragma in a prefix header and then only
selectively disable it around system header inclusions. They may
only care about binary compatibility with MSVC for a subset of
those structs, but that doesn't mean they have no binary
compatibility concerns at all for the rest; thus we are essentially
forced into supporting this hybrid ABI. But it's reasonable for
us to at least point out the places where we're not making
any guarantees.
The original diagnostic was for dynamic classes, i.e. those with
virtual functions or virtual bases; I've extended it to include
all classes with bases, because we are not actually making any
attempt to duplicate MSVC's base subobject layout in ms_struct
(and it is indeed quite different from Itanium, even for
non-virtual bases).
rdar://16178895
llvm-svn: 202427
This was changed to use manual desugaring and multiplication in r201832
and fixed for multi-dimensional arrays in r201917. However, it breaks
down in the presence of typedefs. Rather than attempting to handle all
the desugaring, just go back to calling the generic type info code.
This was discovered while compiling SIInstrWaits.cpp in the R600
backend.
llvm-svn: 202175
A recent change caused multi-dimensional arrays not to be handled
correctly, this patch fixes that. Also, it adds a lit test for
multi-dimensional arrays.
llvm-svn: 201917
Slight change to the way zero-sized sub-objects are tracked in the
presence of virtual bases.
In addition we correctly distinguish between dsize and nvsize.
addresses http://llvm.org/bugs/show_bug.cgi?id=18826
Unit tests are included.
llvm-svn: 201832
This reverts commit r201810.
It was failing these tests on my workstation:
Clang :: CodeGen/override-layout.c
Clang :: CodeGenCXX/override-layout.cpp
Clang :: PCH/check-deserializations.cpp
llvm-svn: 201823
External sources shouldn't prevent the layout engine from using
MSLayout. If lldb were to support debugging in microsoft mode, some
code will need to be added to MSRecordLayoutBuilder to handel external
layouts.
llvm-svn: 201810
According to the GNU docs, zero-sized bitfields should not be affected by the
packed attribute.
Differential Revision: http://llvm-reviews.chandlerc.com/D2693
llvm-svn: 201288
useBitFieldTypeAlignment() and appears to ignore the special
bit-packing semantics of __attribute__((packed)).
Further flesh out an already-extensive comment.
llvm-svn: 201282
These features are new in VS 2013 and are necessary in order to layout
std::ostream correctly. Currently we have an ABI incompatibility when
self-hosting with the 2013 stdlib in our convertible_fwd_ostream wrapper
in gtest.
This change adds another implicit attribute, MSVtorDispAttr, because
implicit attributes are currently the best way to make sure the
information stays on class templates through instantiation.
Reviewers: majnemer
Differential Revision: http://llvm-reviews.chandlerc.com/D2746
llvm-svn: 201274
vptr injection must inject padding equivalent to the alignment of the
most aligned non-virtual subobject, not the alignment of the enclosing
record.
To fascilitate this change, don't let record layout observe the
alignment of the record until we've injected our vptrs. Also, do not
allow the alignment of vbases to affect required alignment until just
before we insert the vtordisp field.
llvm-svn: 201199
This patch makes a small behavioral change to the interaction between
pack and alignment. Specifically it makes __declspec(align()) on a
field change that field's alignment without respect to pack but the
alignment change to the record alignment as a whole still obeys pack.
llvm-svn: 199172
Although VBPtrs were being placed correctly by the ms-abi layout engine,
their offsets were being improperly reported to the ASTRecordLayout
builder due to a bug. This patch fixes that and fixes the test cases to
use the correct values.
y
llvm-svn: 199168
This patch moves the check for pragma pack until after the application
of __declspec align to before pragma pack. This causes observable
changes in the use of tail padding for bases. A test case is included.
llvm-svn: 199154
The MS-ABI tracks a bit that asserts that the first sub-object is zero
sized. This bit is used to add padding between objects if there's the
potential for zero sized objects to alias. The bit is still true even
if the zero sized base is lead by a VFPtr. This patch makes clang mimic
that behavior.
llvm-svn: 199132
This patch more cleanly seperates the concepts of Preferred Alignment
and Required Alignment. Most notable that changes to Required Alignment
do *not* impact preferred alignment until late in struct layout. This
is observable when using pragma pack and non-virtual bases and the use
of tail padding when laying them out.
Test cases included.
llvm-svn: 198988
The presence of a VBPtr suppresses the presence of zero sized
sub-objects in the non-virtual portion of the object in the context of
determining if two base objects need alias-avoidance padding placed
between them.
Test cases included.
llvm-svn: 198975
__declspec(align), when applied to bitfields affects their perferred
alignment instead of their required alignment. We don't know why.
Also, #pragma pack(n) turns packing *off* if n is greater than the
pointer size. This is now observable because of the impact of
declspec(align) on bitfields.
llvm-svn: 198907
The MS abi lays out *all* non-virtual bases with leading vfptrs before
laying out non-virutal bases without vfptrs. This guarantees that the
primary base is laid out first. r198818 fixed RecordLayoutBuilder to
produce compatiable layouts. This patch fixes CGRecordLayoutBuilder to
be able to consume those layouts and produce meaningful output without
tripping any asserts about assumed incoming layout.
A test case is included that shows CGRecordLayoutBuilder in fact
produces output in the compatiable order.
llvm-svn: 198900
This patch refactors microsoft record layout to be more "natural". The
most dominant change is that vbptrs and vfptrs are injected after the
fact. This simplifies the implementation and the math for the offest
for the first base/field after the vbptr.
llvm-svn: 198818
With pragma pack, the layout engine would produce vfptrs that were
packed width rather than pointer width. This patch addresses the issue
and adds a test case.
llvm-svn: 198059
The alignment impact of the virtual bases apperas to be applied in
order, rather than up front. This patch adds the new behavior and
provides a test case.
llvm-svn: 197639
This refactor addresses bugzilla bug 18167 and simplifies the code at
the same time. Also I add a test case for the bug. Also I make a
non-functional change to the basic layout lit tests to make them more
reliable (using CHECK-NEXT instead of CHECK).
llvm-svn: 197183
After r196549 there is no need to separate FinalizeCXXLayout and
FinalizeLayout so they were merged and FinalizeCXXLayout was eliminated.
llvm-svn: 197083
Prior to this patch, the alignment imposed by virtual bases only
included direct virtual bases. This patch fixes it to look at all
virtual bases.
llvm-svn: 196997
In order to address latent bugs that were easier to expose in 64-bit
mode, we move the application of __declspec(align) to before the layout
of vbases rather than after.
llvm-svn: 196861
MS-ABI adds padding before *every* vbase if the last field in a record
is a bit-field. This changes clangs behavior to match. I also fix some
windows-style line endings in the test file.
Differential Revision: http://llvm-reviews.chandlerc.com/D2277
llvm-svn: 196605
Adds padding between bases or virtual bases in an attempt to avoid
aliasing of zero-sized sub-objects. The approach used by the ABI adds
two more bits of state. Detailed comments are in the code. Test cases
included.
Differential Revision: http://llvm-reviews.chandlerc.com/D2258
llvm-svn: 196602
__declspec(align())
This patch implements required alignment in a way that makes
__declspec(align()) and #pragma pack play correctly together. In the
MS-ABI, __declspec(align()) is a hard rule and cannot be overridden by
#pragma pack. This cases each record to have two interesting alignments
"preferred alignment" (which matches Itanium's concept of alignment) and
"required alignment" which is an alignment that must never be violated,
even in the case of #pragma pack. This patch introduces the concept of
Required Alignment to the record builder and tracks/uses it
appropriately. Test cases are included.
Differential Revision: http://llvm-reviews.chandlerc.com/D2283
llvm-svn: 196549
Microsoft adds an extra byte of padding before laying out zero sized
non-virtual bases if the non-virtual base before it contains a vbptr.
This patch adds the same behavior to clang.
Differential Revision: http://llvm-reviews.chandlerc.com/D2106
llvm-svn: 195158
Differential Revision: http://llvm-reviews.chandlerc.com/D2090
Clang was "improperly" over-aligning arrays with sizes are not a multiple of
their alignment.
This behavior was removed in microsoft 32 bit mode.
In addition, after examination of ASTContext::getTypeInfoImpl, a redundant code block in
MicrosoftRecordLayoutBuilder::getAdjustedFieldInfo was deleted.
llvm-svn: 193898
it. Also removes all of the microsoft C++ ABI related code from the
itanium layout builder.
Differential Revision: http://llvm-reviews.chandlerc.com/D2003
llvm-svn: 193290
We have to reserve at least the width of a pointer for the vfptr. For
classes with small alignment, we weren't reserving enough space, and
were overlapping the first field with the vfptr.
llvm-svn: 192626
This patch fixes the distructor test when checking for vtordisp requirements in
microsoft record layout. A test case is also included.
Addresses:
http://llvm.org/bugs/show_bug.cgi?id=16406#c7
llvm-svn: 192616
these in eagerly if we're not actually processing a translation unit. The added
laziness here also avoids us loading in parts of a CXXRecordDecl earlier than an
upcoming class template specialization merging patch would like.
Ideally, we should mark the vtable as used when we see a definition for the key
function, rather than having a separate pass over dynamic classes at the end of
the TU. The existing approach is pretty bad for PCH/modules, since it forcibly
loads the declarations of all key functions in all imported modules, whether or
not those key functions are defined.
llvm-svn: 189627
The record layout code didn't properly take into account that
an empty class at offset 0 can have an alignment greater than 1.
Patch by Andrea Di Biagio.
llvm-svn: 186370
The old implementation of ms_struct in RecordLayoutBuilder was a
complete mess: it depended on complicated conditionals which didn't
really reflect the underlying logic, and placed a burden on users of
the resulting RecordLayout. This commit rips out almost all of the
old code, and replaces it with simple checks in
RecordLayoutBuilder::LayoutBitField.
This commit also fixes <rdar://problem/14252115>, a bug where class
inheritance would cause us to lay out bitfields incorrectly.
llvm-svn: 185018
When the decl that we're getting alignment for is a FieldDecl, and the field's
parent record is invalid, skip the actual field alignment calculation (and
return 1-byte alignment in the general case).
Also, assert in in getASTRecordLayout that the decl is valid. This was
inspired by PR16292; see also r184581 and r184751.
llvm-svn: 184883
MSVC's class data is always comdat, so clang's should always be
linkonce_odr in LLVM IR.
Reviewers: pcc
Differential Revision: http://llvm-reviews.chandlerc.com/D838
llvm-svn: 182865
Most of the complexity of this patch is figuring out which types get the
qualifier and which don't. If we implement __ptr32/64, then we should
check the qualifier instead of assuming all pointers are 64-bit.
This fixes PR13792.
Patch by Warren Hunt!
llvm-svn: 181825
Aaron Ballman