Concerns about the cross-tools detection change.

[Brooks Moses]

Hello!

We recently tried building one of our libraries for the Cell processor 
on a cross-compile setup using autoconf 2.61, and got the following warning:

--------------------
checking for powerpc-ibm-linux-gnu-ppu-gcc... no
checking for powerpc-ibm-linux-gnu-ppuxlc... no
checking for ppu-gcc... ppu-gcc
configure: WARNING: In the future, Autoconf will not detect cross-tools
whose name does not start with the host triplet.  If you think this
configuration is useful to you, please write to address@hidden
--------------------

Thus, I am following directions and sending this email.

This proposed change is a signficant problem with regards to systems 
like IBM's Cell SDK, where a vendor supplies cross-compilers with names 
that clearly denote the fact that they are not native compilers, yet 
happen not to conform to the GNU host-triplet prefixes.

This is particularly annoying with regards to the AC_PROG_CC([ppu-gcc 
ppuxlc]) form of the directive.  According to the documentation, what 
that means is that autoconf should select a compiler from the list I 
have given it.  When I tell the system explicitly what compilers I wish 
to use, it seems to me that it should follow the documentation and do 
what I say; it should not disregard my clear wishes and insist on doing 
a misguided version of what it thinks I mean instead.

Also, from what I can see, there is no fully functional workaround.  The 
only documented one I have found is to create symlinks from 
powerpc-ibm-linux-gnu-ppu-gcc to ppu-gcc in /usr/local/bin.  This might 
be workable for a proprietary library that is built on the programmer's 
machine and only distributed in binary form; however, for our case where 
we provide GPL-licensed source to our users to enable them to build the 
library for themselves, this adds another (entirely pointless) step 
which we will have to explain to our users.

Thus, we would very strongly ask that this proposed change _only_ apply 
to the form of AC_PROG_CC with an implicit list of compilers (if it is 
indeed implemented at all), and that the form of AC_PROG_CC with an 
explicit list of compilers continue to act as documented in the manual, 
and select compilers from the list that has been supplied, in the form 
that they are given.

If that is not possible, I would like to know of a workaround that (a) 
provides all of the functionality of AC_PROG_CC, (b) will select from 
multiple options, and (c) does not require extra steps for our users.

Thank you,
- Brooks