[distcc] gcc bootstraps with distcc

[Alexandre Oliva]

On Jul 11, 2003, "Zack Weinberg" <zack at codesourcery.com> wrote:

> Thank you for the clear explanation.  The conclusion I draw from it is
> that we should turn this mode on when and only when it affects the
> output of the compiler.

I.e., whenever debugging is enabled.  This will still defeat ccache,
since the default value of CFLAGS chosen by autoconf when compiling
with GCC is "-O2 -g", even if binaries are stripped at install time,
like they most often are.

The reason I'd rather not have this option on by default is that it
would require changes for those who build their huge applications
using a shared cache for ccache, with a benefit that, AFAICT, would be
pretty much limited to GCC bootstraps.

Since no other compiler I'm aware of requires an option to get ccache
to get cache hits for builds in different directories, I kind of want
GCC to behave the same, even though this is arguably incorrect
behavior.  But then, arguably, if you got a cache hit from a different
source tree, odds are that you'll still find the sources used for that
build in that directory, and everything will be fine.  Sure enough, if
this is not the case, debugging the problem may be tricky until you
realize what's going on.

I think I have put all my arguments on the table, and it's time to
make a decision.  Any final opinions on what the default should be?

> Would you, Martin, be willing to do some research and figure out
> under exactly what conditions this makes a difference?

The only occurrences of getpwd() in the compiler proper are changed in
my patch.  It's only debugging info.

> Also, I agree with Neil, this has nothing to do with dependency
> output, it shouldn't be an -M option.

Doh.  I for some reason thought -M stood for `preprocessor options'.

> If it affects only debug information, let's make it -g(no-)pwd

Sold :-)

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva@{redhat.com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist                Professional serial bug killer