When I try to compile glibc 2.6.1 with gcc 3.4.3 (cross-compiler), configuring 
glibc fails with the following error message:

running configure fragment for sysdeps/unix/sysv/linux/powerpc
checking whether powerpc-unknown-linux-gcc -g -O2 -mlong-double-128 uses IBM 
extended format... no
checking whether powerpc-unknown-linux-gcc -g -O2 
supports -mabi=ibmlongdouble... no
configure: error: this configuration requires -mlong-double-128 IBM extended 
format support

------- Additional Comment #1 From Bart Van Assche 2007-08-29 11:47 -------

Created an attachment (id=1975)
glibc (cross-)compilation script

------- Additional Comment #2 From Ulrich Drepper 2007-08-29 15:45 -------

You get told what to do.  If you don't have these features you cannot use glibc.
 It's that simple.  Don't make your problems ours.  There might be something in
the ports tree which can help but this is of no interest here.  Do not pollute
bz with any of this.

------- Additional Comment #3 From Jakub Jelinek 2007-08-29 15:55 -------

Yeah, if you read INSTALL, you can see it clearly:
On other machines, GCC 4.1 is required to build the C
library with support for the correct `long double' type format;
these include `powerpc' (32 bit), `s390' and `s390x'.

------- Additional Comment #4 From Bart Van Assche 2007-08-29 16:13 -------

(In reply to comment #3)
> Yeah, if you read INSTALL, you can see it clearly:
> On other machines, GCC 4.1 is required to build the C
> library with support for the correct `long double' type format;
> these include `powerpc' (32 bit), `s390' and `s390x'.

You are right -- sorry that I overlooked this information. I had been grepping
through the glibc sources for long-double (with dash), that's why I didn't find
this information. Google wasn't helpful either.