Cross-compiling is broken. Help me fix it.

[Brad Garcia]

I'm attempting to cross-compile this library (host i686-pc-linux-gnu,
target i386-lynx-lynxos).  I've run into several problems.

The first thing I did was to set some environment variables so that the
correct compilers would be used.  In particular I did the following:

    setenv AR     i386-lynx-lynxos-ar
    setenv AS     i386-lynx-lynxos-as
    setenv CC     i386-lynx-lynxos-gcc
    setenv CXX    i386-lynx-lynxos-g++
    setenv LD     i386-lynx-lynxos-ld
    setenv NM     i386-lynx-lynxos-nm
    setenv RANLIB i386-lynx-lynxos-ranlib

I ran configure with the following options:

    ../libstdc++-2.90.7/configure
    --prefix=/usr/local/libstdc++/2.90.7/i386-lynx-lynxos
    --with-gnu-ld
    --host=i686-pc-linux-gnu
    --target=i386-lynx-lynxos

Everything is fine until the byte-ordering check:

    checking whether byte ordering is bigendian... configure: error: can
    not run test program while cross compiling

Ok, so I go in and hack that part of the configure script to simply assume
little endian instead of quitting with that error message.  Configuration
now finishes.  But during the make, I run into the following problem:

    make[2]: Entering directory `/home2/bgarcia/dload/libstdc++/lynx/src'
    /bin/sh ../../libstdc++-2.90.7.new/mknumeric_limits `pwd`/.. ../../libstdc++-2.90.7.new
    running mknumeric_limits
    /tmp/ccql0Mmf.o(.text+0xbc3):gen-num-limits.cc: undefined reference to
    `value<bool>::epsilon'
    (...(and about 20 more similar error messages)...

So I take a look at mknumeric_limits.
It appears to be attempting to create a file called gen-num-limits.cc,
compile it into a program called gen-num-limits, and then run that
program to produce std_limits.h.  There's at least one problem with that:

1) It's attempting to use CXX (in my case i386-lynx-lynxos-g++) to compile
   the program.  Using a cross-compiler does not seem like the right thing
   to do here.

Ok, so I hack mknumeric_limits and change all occurrences of CXX to
HOST_CXX, which defaults to g++.  Now I try to build again and get the
following:

    i386-lynx-lynxos-g++ -DHAVE_CONFIG_H -I. -I../../libstdc++-2.90.7.new/src -I.. -nostdinc++ -I../../libstdc++-2.90.7.new/config/default -I../../libstdc++-2.90.7.new -I../../libstdc++-2.90.7.new/stl -I../../libstdc++-2.90.7.new/libio -D_GNU_SOURCE -fno-implicit-templates -Wall -Wno-format -W -Wwrite-strings -Winline -Werror -g -fno-honor-std -c ../src/limitsMEMBERS.cc -o limitsMEMBERS.o
    In file included from ../src/limitsMEMBERS.cc:37:
    ../bits/std_limits.h: In function `static long double numeric_limits<long double>::min()':
    ../bits/std_limits.h:690: no field `__convert_long_double_i' in union being initialized
    ../bits/std_limits.h:690: confused by earlier errors, bailing out
    make[2]: *** [../src/limitsMEMBERS.lo] Error 1

So now it appears that std_limits.h is relying on my host-machine's header
files (float.h, which has __convert_long_double_i defined).  I'm not sure
how to work around this problem.

If anybody has a suggestion, I'm open to them.

Brad Garcia