This diagnostic (which defaults to an error, added in
95833f33bd) was intended to clearly
point out cases where the C++ ABI won't match the Microsoft C++ ABI,
for cases when this is enabled via a pragma over a region of code.
The MSVC compatible struct layout feature can also be enabled via a
compiler option (-mms-bitfields). If enabled that way, one essentially
can't compile any C++ code unless also building with
-Wno-incompatible-ms-struct (which GCC doesn't support, and projects
developed with GCC aren't setting).
For the MinGW target, it's expected that the C++ ABI won't match
the MSVC one, if this option is used for getting the struct
layout to match MSVC.
Differential Revision: https://reviews.llvm.org/D81794
(Keep -Wmsvc-include around as an alias.)
While here, also replace the one other mention of "MSVC" in diagnostics with
"Microsoft", for consistency.
llvm-svn: 243444
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
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
Martin Storsjö