cpp problem with asm

[Jonathan Larmour <jlarmour at redhat dot com>]

Hi guys,

First off, I know there have been points made here that cpp is not
supported with languages other than C/C++, and I've read the relevant bit
of cpp.texi. Still, it is useful for preprocessing assembler, and even the
driver recognises that by accepting .S files and passing -lang-asm to cpp0,
which then knows to not complain about unknown directives (in
cpplib.c:354). However there is still a problem:

The issue is revealed in the following snippet. The "# foo" etc. would be
assembler comments.

#if 0           // must be false
        # foo
        # fee
        # fie
        # foe   only this one
        # fum   and this one are reported
        
#elif 0         // dont care
        # bundy
#endif

If this is saved as foo.S, and compiled with (e.g.) "sh-elf-gcc -Wundef -E
foo.S" with current gcc, we get:

foo.S:6:11: warning: "fum" is not defined
foo.S:5:11: warning: "foe" is not defined
foo.S:5:11: missing binary operator

Curiously, as described, this only matters when a #elif is present and the
#if is false. The only tokens reported are the latter two.

I think the code at cpplib.c:354 isn't correct. It does not result in the #
and token just being output verbatim - instead it is put in the lookahead
list for possible processing in subsequent directives. I think.

So can anyone wiser about cpp have a look or give me more pointers? Thanks.

Jifl
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