Hi Christoph,
Am 08.07.2021 um 16:31 schrieb Christoph Hellwig:
On Wed, Jul 07, 2021 at 08:01:33PM -0700, Linus Torvalds wrote:
The '#' turns the argument into a string, but it was already
_supposed_ to be a string. But no, the problem is that it turns the
macro name MOVES into the _string_ "MOVES".
Which happens to compile just fine, because "moves" is a real
instruction. But it's actually _meant_ to be a macro that expands to
either the string "moves" or "move".
So what happens is that at least in Christoph's version, I think the
code _always_ uses "MOVES", even in configurations where the macro
MOVES should have just become "move".
So it all builds fine, looks fine to the assembler, but it uses the
wrong instruction.
Macro expansion with the '#' character and other macros used as
arguments is something people need to be very careful with. It's why
we have a whole header file for just the "stringify" operation, see
<linux/stringify.h>
But in this case, it shouldn't have used '#' at all, since the
argument was already a string, and never needed to be turned into a
string by the pre-processor.
Yes, that problem exists, but just removing the # causes "inst" to go
into the cpp output. Let me brush up my cpp-foo.
Putting quotes around 'inst' makes it compile for me.
Cheers,
Michael
