Summary:
Our usual definition of max_align_t wouldn't match up with MSVC if it
was used in a template argument.
Reviewers: chandlerc, rsmith, rnk
Reviewed By: chandlerc
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D2924
llvm-svn: 202911
This definition is not chosen idly. There is an unfortunate reality with
max_align_t -- the specific nature of its definition leaks into the ABI
almost immediately. Because it is part of C11 and C++11 it becomes
essential for it to match with other systems on that ABI. There is an
effort to discourage any further use of this construct as a consequence
-- using max_align_t introduces an immediate ABI problem. We can never
update it to have larger alignment even as the microarchitecture changes
to necessitate higher alignment. =/
The particular definition here exactly matches the ABI of GCC's chosen
::max_align_t definition, for better or worse. This was written with the
help of Richard Smith who was decoding the exact ABI implications of the
selected definition in GCC. Notably, in-register arguments are impacted
by the particular definition chosen. =/
No one is under the illusion that this is a "good" or "useful"
definition of max_align_t, and we are working with the standards
committee to specify a more useful interface to address this need.
llvm-svn: 201729
This adds a test to make sure we define _WCHAR_T_DEFINED and
_NATIVE_WCHAR_T_DEFINED correctly in the preprocessor, and updates
stddef.h to set it when typedeffing wchar_t.
llvm-svn: 180918
Per feedback by Doug, we should avoid platform-specific implementations
in lib/Headers as much as possible.
This reverts commit r178110.
llvm-svn: 178181
Clang's <stddef.h> provides definitions for the C standard library
types size_t, ptrdiff_t, and wchar_t. However, the system's C standard
library headers tend to provide the same typedefs, and the two
generally avoid each other using the macros
_SIZE_T/_PTRDIFF_T/_WCHAR_T. With modules, however, we need to see
*all* of the places where these types are defined, so provide the
typedefs (ignoring the macros) when modules are enabled.
llvm-svn: 177686
consensus was that it was fine; iso646 is trivial.
We actually don't need that many headers overall... on Ubuntu, at least,
all we need are stdint.h, stdarg.h, limits.h, and float.h to stop
depending on having gcc's headers around for normal code.
On a side note, the path searching needs some improvement; I had to
hardcode the path to my header directory into clang.cpp to get the
driver to use it consistently.
llvm-svn: 51317
David Majnemer