x86 crosscompile

[Marcus Furlong]

Hi,

I've seen conflicting information about what configure flags to use when 
cross-compiling for a lower x86 architecture on an x86. For example 
cross-compiling for a i486 on an i686. Not even sure if this should be 
called crosscompiling?

For most packages you just need to set CFLAGS or similar to include -march 
for the lower platform, but for some packages setting --host= and --target= 
is needed, especially gcc, glibc and binutils.

see 
http://www.linuxfromscratch.org/hints/downloads/files/crosscompiling-x86.txt 
for examples.

This gives a warning message at the start of each compilation because a 
crosscompiler is not detected, and I was wondering if --build= is the 
appropriate arg to use instead (seeing as we're already probably already 
lying about the build architecture via uname).

e.g. building for an i486 on a i686
is the following correct?

./configure --build=i486-pc-linux-gnu

instead of

./configure --host=i486-pc-linux-gnu --target=i486-pc-linux-gnu

Thanks,

Marcus.

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