Re: __initcall macros and C token pasting

[viro@parcelfarce.linux.theplanet.co.uk]

On Sat, Sep 25, 2004 at 01:57:37PM -0400, Jon Smirl wrote:
> #define DRM(x) r128_##x
> module_init( DRM(init) );
> 
> #define __define_initcall(level,fn) \
>         static initcall_t __initcall_##fn __attribute_used__ \
>         __attribute__((__section__(".initcall" level ".init"))) = fn
> 
> This gives the error:
> {standard input}: Assembler messages:
> {standard input}:104: Error: junk at end of line, first unrecognized
> character is `('
> 
> I believe this is because the C macro is not being expanded in the
> assembler context of the section with the fn assignment.

BS.  In non-modular case (quoted above) DRM(init) will be expanded _long_
before you get to __define_initcall() expansion.

In the modular case, OTOH, it will _not_.  There you get
module_init(DRM(init))  =>
static inline initcall_t __inittest(void) { return initfn; } int init_module(void) __attribute__((alias("DRM(init)")));
since # suppresses expansion of argument.  Which leaves you with
.globl init_module
	.set init_module, DRM(init)
in assembler output.  Which is not going to make as(1) happy.

> Any ideas on how to fix this?

To fix what, exactly?  Your beliefs?  DRM abuse of cpp?  For the former I'd
suggest learning C (or learning to use -S to see what exactly as(1) gets to
deal with).  For the latter...

#define DRM_abuses_cpp_too_fscking_much(x) module_init(x)
DRM_abuses_cpp_too_fscking_much(DRM(init))

will force the expansion before it gets to module_init(), which will result in
acceptable alias.