MFC r260311, r260831:

gcc: Add support for Apple's Block extension

Block objects [1] are a C-level syntactic and runtime feature. They
are similar to standard C functions, but in addition to executable
code they may also contain variable bindings to automatic (stack)
or managed (heap) memory. A block can therefore maintain a set of
state (data) that it can use to impact behavior when executed.

This port is based on Apple's GCC 5646 with some bugfixes from
Apple GCC 5666.3. It has some small differences with the support
in clang, which remains the recommended compiler.

Perhaps the most notable difference is that in GCC __block is not
actually a keyword, but a macro. There may be workaround for this
issue in the future. Other issues can be consulted in the clang
documentation [2]

For better compatiblity with Apple's GCC and llvm-gcc, some related
fixes and features from Apple have been included. Support for the
non-standard nested functions in GCC is now off by default.

No effort was made to update the ObjC support since FreeBSD doesn't
carry ObjC in the base system but some of the code crept in and
was more difficult to remove than to adjust.

References:
[1]
https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Blocks/Articles/00_Introduction.html
[2]
http://clang.llvm.org/compatibility.html#block-variable-initialization

Obtained from: Apple GCC 4.2

MFC r260014, r260099:

gcc: Add support for label attributes and "unavailable" attribute.

Apple GCC has extensions to support for both label attributes and
an "unavailable" attribute. These are critical for objc but are
also useful in regular C/C++.

Obtained from: Apple GCC 4.2 - 5531

MFC r259666, r259696:

gcc: warnings from -Wformat-security

Obtained from: Apple GCC 4.2 - 5646 (Radar 5764921)

MFC r258081, r258138, r258143, r258179, r258157, r258204, 258205,
r258206, r258207, r258321

This is a series of commits inspired on Google's gcc-4.2.1 for
Android that were taken from the gcc pre-4.3 under the GPLv2.

gcc: Backport fixes for -W parentheses in C++
This fixes GCC 19564.
gcc: merge rs6000 change from FSF pre-gcc43
Don't set MASK_PPC_GFXOPT for 8540 or 8548.
Merge vrp-tree fix from gcc-4.3
Fix missed conversion from / to >> (GCC PR32521)
Merge in GCCr120505 to include definition of TREE_OVERFLOW_P
gcc: warn about integer overflow in constant expressions in the C++ frontend.
gcc: Add a new option -Wvla to warn variable length array.
libcpp: preprocessor speedup patches from upstream gcc.
gcc: add femit-struct-debug support to reduce Reduce dwarf debug size
gcc: Fix postreload-gcse treatment of call-clobbered registers.
gcc: Record some previous commits in the ChangeLog.gcc43 file.

MFC r260311, r260831:

gcc: Add support for Apple's Block extension

Block objects [1] are a C-level syntactic and runtime feature. They
are similar to standard C functions, but in addition to executable
code they may also contain variable bindings to automatic (stack)
or managed (heap) memory. A block can therefore maintain a set of
state (data) that it can use to impact behavior when executed.

This port is based on Apple's GCC 5646 with some bugfixes from
Apple GCC 5666.3. It has some small differences with the support
in clang, which remains the recommended compiler.

Perhaps the most notable difference is that in GCC __block is not
actually a keyword, but a macro. There may be workaround for this
issue in the future. Other issues can be consulted in the clang
documentation [2]

For better compatiblity with Apple's GCC and llvm-gcc, some related
fixes and features from Apple have been included. Support for the
non-standard nested functions in GCC is now off by default.

No effort was made to update the ObjC support since FreeBSD doesn't
carry ObjC in the base system but some of the code crept in and
was more difficult to remove than to adjust.

References:
[1]
https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Blocks/Articles/00_Introduction.html
[2]
http://clang.llvm.org/compatibility.html#block-variable-initialization

Obtained from: Apple GCC 4.2

MFC r260014, r260099:

gcc: Add support for label attributes and "unavailable" attribute.

Apple GCC has extensions to support for both label attributes and
an "unavailable" attribute. These are critical for objc but are
also useful in regular C/C++.

Obtained from: Apple GCC 4.2 - 5531

MFC r259666, r259696:

gcc: warnings from -Wformat-security

Obtained from: Apple GCC 4.2 - 5646 (Radar 5764921)

MFC r258081, r258138, r258143, r258179, r258157, r258204, 258205,
r258206, r258207, r258321

This is a series of commits inspired on Google's gcc-4.2.1 for
Android that were taken from the gcc pre-4.3 under the GPLv2.

gcc: Backport fixes for -W parentheses in C++
This fixes GCC 19564.
gcc: merge rs6000 change from FSF pre-gcc43
Don't set MASK_PPC_GFXOPT for 8540 or 8548.
Merge vrp-tree fix from gcc-4.3
Fix missed conversion from / to >> (GCC PR32521)
Merge in GCCr120505 to include definition of TREE_OVERFLOW_P
gcc: warn about integer overflow in constant expressions in the C++ frontend.
gcc: Add a new option -Wvla to warn variable length array.
libcpp: preprocessor speedup patches from upstream gcc.
gcc: add femit-struct-debug support to reduce Reduce dwarf debug size
gcc: Fix postreload-gcse treatment of call-clobbered registers.
gcc: Record some previous commits in the ChangeLog.gcc43 file.