Hi Nathan,
On Wed, Jun 24, 2020 at 6:02 AM Nathan Chancellor
<natechancel...@gmail.com> wrote:
> arch/powerpc/boot/main.c:107:18: warning: array comparison always
> evaluates to a constant [-Wtautological-compare]
> if (_initrd_end > _initrd_start) {
> ^
> arch/powerpc/boot/main.c:155:20: warning: array comparison always
> evaluates to a constant [-Wtautological-compare]
> if (_esm_blob_end <= _esm_blob_start)
> ^
> 2 warnings generated.
>
> These are not true arrays, they are linker defined symbols, which are
> just addresses. Using the address of operator silences the warning
> and does not change the resulting assembly with either clang/ld.lld
> or gcc/ld (tested with diff + objdump -Dr).
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/212
> Reported-by: Joel Stanley <j...@jms.id.au>
> Signed-off-by: Nathan Chancellor <natechancel...@gmail.com>
> ---
> arch/powerpc/boot/main.c | 4 ++--
> arch/powerpc/boot/ps3.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
> index a9d209135975..cae31a6e8f02 100644
> --- a/arch/powerpc/boot/main.c
> +++ b/arch/powerpc/boot/main.c
> @@ -104,7 +104,7 @@ static struct addr_range prep_initrd(struct addr_range
> vmlinux, void *chosen,
> {
> /* If we have an image attached to us, it overrides anything
> * supplied by the loader. */
> - if (_initrd_end > _initrd_start) {
> + if (&_initrd_end > &_initrd_start) {
>
Are you sure that fix is correct?
extern char _initrd_start[];
extern char _initrd_end[];
extern char _esm_blob_start[];
extern char _esm_blob_end[];
Of course the result of their comparison is a constant, as the addresses
are constant. If clangs warns about it, perhaps that warning should be moved
to W=1?
But adding "&" is not correct, according to C.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
