Re: [gentoo-user] How to properly change CFLAGS ?

[Alan Mckinnon]

On Tue, 2006-08-22 at 11:40 -0700, Richard Fish wrote:
> On 8/22/06, Alan Mckinnon <alan@××××××××××××××××.za> wrote:
> > Your current compiler was built with -O3, and you want to rebuild the
> > system using a compiler compiled as -O2, hence the 2 step process.
>
> *Sigh*.  I am so tired of this completely wrong information showing up here.
>
> 1. It does not matter what -OX flag gcc is compiled with.  It has
> absolutely *zero* effect on the code that gcc *generates*.
>
> 2. There is also absolutely no reason to build gcc twice.  There is no
> such thing as a gcc that was built with the "system compiler", because
> gcc uses itself to build itself.  It is called a 3-stage bootstrap,
> and I suggest you read the gcc documentation first if you want to
> debate this point.

I have read the docs, several times. I was replying to a confessed
newbie so had to keep it simple so he had a chance of understanding the
big picture and also not fscking his system. You and I could probably
fix that if it happened to us, the OP probably could not. There's more
at stake here than just gcc - there's an entire toolchain which very
very few people actually understand, including most people on this list.

Incidentally, gcc cannot use itself to compile itself - that's
nonsensical and a classic bootstrap problem. It uses a binary (which
happens to be a gcc) to compile the source code for gcc which produces
another binary. That binary then compiles the same source for gcc to
produce yet another binary, etc, etc. For stage 1 to work at all, there
has to be a compiler available to compile a compiler, and that first
compiler that *must* be available is probably the compiler that the rest
of the system uses, or the one on the LiveCD. So if you want to be
pedantic about building gcc, then please be correctly pedantic and
pedantically correct :-)

alan


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