On older Apple compilers "-O4" is known to cause build errors. On recent
clang, it's the same as "-O3" and you have to pass "-O3 -flto" to get
the old behavior.
It is activated by the same mechanism as the Homebrew/versions compilers
which now check if the GCC formula uses the same, correct version.
References Homebrew/homebrew#28418.
Rationale: our arg refurbishment is normally only turned on when
called via the `make` wrapper, for compatibility reasons. However,
there are numberous places we'd like this to be turned on elsewhere,
like software that builds via `python setup.py` where bad flags from
the system python can be pulled in.
This helper appends 'O' to CCCFG, which enables refurbishment for
all calls of the compiler shims.
This flag no longer affects the output of the compiler wrappers, since
everything is buffered by the build process rather than each individual
tool.
Additionally, this is a user-facing knob that affects ARGV.verbose?, and
the combination of these two issues broke the --quieter feature.
The mapping of architectures to optimization flags is now retrieved from
Hardware::CPU and the selected flags are passed as an environmen
variable, rather than duplicated in the cc wrapper and re-calculated on
every invocation of the compiler.
ClosesHomebrew/homebrew#24540.
Constructing the path relative to a file in the repository is incorrect
on some supported configurations (i.e., the repository is located in a
different place than the prefix).
ClosesHomebrew/homebrew#24418.
The cc wrapper's make_fuss is only enabled when HOMEBREW_CCCFG contains
'O', which is set by the make wrapper. This means it is disable when
running configure scripts. However, this does not include configure
scripts invoked by make, which inherit the value of HOMEBREW_CCCFG from
the make process. make_fuss will be enabled for these scripts, cause
breakage.
Configure scripts generated by autoconf 2.56 (November 2002) or later
export DUALCASE into the environment of subprocesses. This variable is
only used by the MKS shell, so we can use it as a heuristic to determine
if we are running as a subprocess of a configure script.
* Add new ENV function for selecting stdlib for Clang.
- The selection is no-op for non-system-clang compilers.
- Both superenv and stdenv are handled.
* Add new HOMEBREW_CCCFG flag and ccwrapper handling.
* Add options and ENV method to specify building in C++11 mode.
- Set C++ compiler flags to enable C++11 mode.
- To add options to support C++11 mode, a formula can now use
option :cxx11
to provide "--c++11" option, and detect and enable C++11 support in
install method using
ENV.cxx11 if build.cxx11?
ClosesHomebrew/homebrew#22453.
