Re: Putting C++ code into gcc front end

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

Nathanael Nerode <neroden at twcny dot rr dot com> writes:

| Gaby wrote:
| > You don't need to install C++ first.  You just need to build C++.
| > And you have to do that anyway if you want libjava/verify.cc.
| > So that is a non-issue.
| 
| Wrong.
| 
| Currently, it works as follows in the non-native case:
| * Build a full copy of gcc, using installed C and Ada compilers.
| * Use this copy of GCC to build libraries.
| 
| This would have to be changed if the Java front end contained C++ code.
| 
| --
| In the bootstrap case it works as follows:
| * Build a C/Ada compiler, using installed C and Ada compilers.  This is 
| the stage1 xgcc.

OK.

| * Use stage1 xgcc to build a full copy of the compiler.  This is stage2 
| xgcc.

OK.

| * Use stage2 xgcc to build another full copy of the compiler.  This is 
| stage3 xgcc (and acts as a test that the C and Ada compilers work).
| 
| Here, if the Java front end contained C++ code, then stage2 xgcc would 
| need to be built with a C++ compiler.

Yes.

| Accordingly, stage1 xgcc would need to *be* a C++ compiler.

No, that does not follow: We never actually bootstrap for the C++
compiler. Currently, we only bootstrap the C compiler and and diff the
objets. That does not act as a test that the C++ compiler works.  It
just does test the C compiler.

To correct your scheme, here is how it could proceed:

 * Use stage1 to build G++:
     + build g++ (which becomes a stage2 compiler)
     + use stage2 g++ to build the C++ runtime system.
       This step is part of using stage2 xgcc to build the full
       compiler. 

No trouble.

-- Gaby