How to compare two text files? Using sed, cmp, diff, tr?

[Kevin]

Georg-Johann Lay wrote:
> The avr backend auto-generates parts of GCC's texi documentation,
> namely the supported -mmcu= options, which are about 200.
>
> To generate the texi a small C program is used to print the texi
> to stdout, and that output is then compared against the already
> existing doc/avr-mmci.texi
>
> If the output is the same like in that file, nothing happens.
>
> If the output differs from that file, the user (someone building the
> avr compiler) is nagged to update the existing documentation so that
> the documentation says in sync with the compiler.
>
> The part of t-avr reads:
>
> s-avr-mmcu-texi: gen-avr-mmcu-texi$(build_exeext)
>     $(RUN_GEN) $< | sed -e 's:\r::g' > avr-mmcu.texi
>     @if cmp -s $(srcdir)/doc/avr-mmcu.texi avr-mmcu.texi; then \
>       $(STAMP) $@;        \
>     else            \
>       echo >&2 ;        \
>       echo "***" >&2 ;    \
>       echo "*** Verify that you have permission to grant a" >&2 ;    \
>       echo "*** GFDL license for all new text in" >&2 ;         \
>       echo "*** avr-mmcu.texi,then copy it to 
> $(srcdir)/doc/avr-mmcu.texi" >&2 ; \
>       echo "***" >&2 ;    \
>       false;         \
>     fi
>
> The problem is comparing the new texi file avr-mmcu.texi against the
> already existing $(srcdir)/doc/avr-mmcu.texi and factor out different
> line endings that depend on the build system like LF vs. CRLF.
>
> What is the best way to do such a comparison on text level without
> getting a complaint if the original texi was built on linux and the
> user builds the compiler under, say, windows?
>
> How to cope with different line endings in that case?
Instead of trying to cope with different line endings on the
generated files, wouldn't it be better to modify the C program
to output the desired line ending format in the first place?
Instead of just writing a \n in text mode, output \n\r in binary
mode (if you want DOS format), or just \n (for unix format).

I'd think changing the line ending format on a file should be
considered a problem, as the distributed files could end up
in numerous formats, making nobody really happy.