= Co-installable Compilers =

It is useful to be able to install compilers built for more than one architecture side by side (e.g. amd64 and i386). This page describes a rearrangement of the packaging which allows that. This scheme also nicely enables cross-compilers using the same layout.

<ver> on this page refers to the gcc version number, (currently (Dec 2014) 4.9).

<triplet> refers to the GNU triplet (e.g. arm-linux-gnueabi)

== Concept ==

Currently we can install gcc-<ver> and gcc-<ver>-<triplet> but you can't install gcc:i386 and gcc:amd64

This is useful (for example because ghc depends on gcc and wanting to install ghc:i386 or ghc:x32 to use less RAM makes a lot of sense). Not a high priority, but is useful and removes arbitrary distinction between compiler and cross-compiler. Makes things nice and orthogonal.

gcc-<ver> is MA:none and cannot simply be made MA:foreign, because it only works properly on the main arch.

ghc:i386 needs gcc(core):i386  but leaving gcc(core):amd64 installed

 * native compilers have BUILD=HOST=TARGET
 * cross-compilers have BUILD=HOST!=TARGET

Currently we have:
 * gcc-<ver> which contains the native compiler
 * and gcc-<ver>-<triplet> which contains a cross-compiler 

so instead we have these packages containing the actual compilers:
{{{
gcc-<ver>-x86_64-linux-gnu
gcc-<ver>-i386-linux-gnu
gcc-<ver>-arm-linux-gnueabihf
}}}
etc

The user installs gcc-ver (arch:any) which is now just symlinks to gcc-<ver>-<triplet> with TARGET=HOST.
so gcc-<ver>-TARGET:HOST ('actual compilers' packages) are MA:foreign

gcc-ver:HOST is MA:none, arch:any, depends on gcc-ver-HOST

So we should be able to install:
 * {{{gcc-ver-TARGET:HOST}}} (cross) and {{{gcc-ver-HOST:HOST}}} (native)
 * {{{g++-ver-TARGET:HOST}}} (cross) and {{{g++-ver-HOST:HOST}}} (native)
at the same time.

 * gcc-4.9-arm-linux-gnueabihf:armhf built from 'gcc-4.9' source. This lives in armhf architecture of repo
 * gcc-4.9-x86_64-linux-gnu:amd64 built from 'gcc-4.9' source.  this lives in amd64 architecture of repo
 * gcc-4.9-arm-linux-gnueabihf:amd64 built from 'cross-gcc-4.9' source. cross-compiler for armhf on amd64
 * gcc-4.9-i386-linux-gnu:amd64 built from 'cross-gcc-4.9' source. cross-compiler for i386 on amd64
 these last 2 live in amd64 architecture of repo

Example patch for tcc: DebianBug:695354

gcc bug: DebianBug:666743