MacPorts wants to install apple-gcc42 on 10.6 all of a sudden?

[Rainer Müller]

On 2013-04-22 16:16, "René J.V. Bertin" wrote:
>> As said, if there is, this is unsupported. You should instead file bugs
>> for the ports that break with clang so they can have clang or broken
>> versions of it selectively blacklisted.
> 
> Sure, but apart from that a user can have good reasons to use a compiler (and/or options) of choice, no? Just one of them: I was amazed to see how much better autovectorisation has become in gcc 4.7 - in one benchmark of code taken from Perian, the 'scalar' version of a YUV conversion routine all of a sudden executed as much faster as a handcoded SSE2 version as that hand-coded version executes w.r.t. the scalar version using gcc-4.2 or MSVC 2010 ...
> I'm using gcc-mp-4.7 whenever I can ever since, not regretting it a bit. 

We do not have resources to handle build errors induced by using various
versions of gcc provided by MacPorts. The general use case is to get a
working installation. Optimizations of the kind described by you are for
intense tasks such as scientific computation or video encoding in
multimedia applications.

For developers, there is a way to set default_compilers from
macports.conf or from the command line to override the automatic
detection based on the Xcode version, but that is not in the default
configuration file. It is meant for developers only and I expect those
who are meant to use this can figure out how it works :-)

Also note that the toolchains provided by Apple (both the old gcc 4.2
and llvm/clang) are patched for use on Mac OS X. Most importantly that
is the introduction of a driver around the normal compilers invoked with
the -arch flags. This allows to build universal binaries in one step,
which is not possible with mainline gcc. Using gcc from MacPorts for
compiling other ports reduces the available features and makes use of
the +universal variant impossible.

Rainer