Re: [PATCH] tools/bootconfig: Fix wrong __VA_ARGS__ usage

[Michael Ellerman]

Masami Hiramatsu <mhiramat@xxxxxxxxxx> writes:
> Since printk() wrapper macro uses __VA_ARGS__ without
> "##" prefix, it causes a build error if there is no
> variable arguments (e.g. only fmt is specified.)
> To fix this error, use ##__VA_ARGS__ instead of
> __VAR_ARGS__.
>
> Fixes: 950313ebf79c ("tools: bootconfig: Add bootconfig command")
> Reported-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
>  tools/bootconfig/include/linux/printk.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks that builds for me.

The output when adding to a fresh initrd is a bit confusing though, eg:

  $ ./bootconfig -a samples/good-simple.bconf initrd.img
  Apply samples/good-simple.bconf to initrd.img
          Number of nodes: 13
          Size: 120 bytes
          Checksum: 9036
  checksum error: 0 != 444373994
  $ echo $?
  0

ie. the checksum error.

That's because although delete_xbc() does:

	pr_output = 0;
	size = load_xbc_from_initrd(fd, &buf);

in load_xbc_from_initrd() the error message is printed with printf, not
printk, so it's not controlled by pr_output:

	printf("checksum error: %d != %d\n", csum, rcsum);

Switching that line to printk fixes it, ie. makes the checksum error go
away, but it seems a bit odd to be using printk in userspace code.

cheers