Messages in this thread | | | Date | Mon, 16 Nov 2015 09:28:09 +0100 | Subject | Re: using IS_ENABLED(CONFIG_xyz) effectively | From | Geert Uytterhoeven <> |
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Hi Vineet,
On Mon, Nov 16, 2015 at 9:00 AM, Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote: > I've been using IS_ENABLED for some time and once in a while run into an issue > which prevents seamless use. Hence posing this question to experts in the area. > > C macro processor evaluates the ensuing control block even if IS_ENABLED evaluates > to false. This requires dummy #defines or worse still removing usage of IS_ENABLED > altogether. > > e.g. In example below even for ARCOMPACT builds, we need the ARCV2 specific define > ARCV2_IRQ_DEF_PRIO. > > void arch_cpu_idle(void) > { > if (is_isa_arcompact()) { <---- IS_ENABLED(CONFIG_ISA_ARCOMPACT) > __asm__("sleep 0x3"); > } else { > const int arg = 0x10 | ARCV2_IRQ_DEF_PRIO; > __asm__("sleep 0x10"); > } > } > > One could argue that the interface needs to be cleanly defined to not have such > specific #defines in common code in first place. However sometime that becomes > just too tedious. > > Is there a way to get around by this ?
Use #ifdef CONFIG_...?
The advantage of IS_ENABLED() over #ifdef is that it allows compile-testing of the disabled code path. Of course it should only be compiled if it makes sense. And that's exactly what you're running into.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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
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