On Wed, 2 May 2018 21:45:00 +0800
[email protected] wrote:
> From: Changbin Du <[email protected]>
>
> With '-Og' optimization level, GCC would not optimize a count for a loop
> as a constant value. But BUILD_BUG_ON() only accept compile-time constant
> values.
>
> arch/arm/mm/mmu.o: In function `fix_to_virt':
> /home/changbin/work/linux/./include/asm-generic/fixmap.h:31: undefined
> reference to `__compiletime_assert_31'
> Makefile:1051: recipe for target 'vmlinux' failed
> make: *** [vmlinux] Error 1
>
> Signed-off-by: Changbin Du <[email protected]>
> ---
> include/asm-generic/fixmap.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
> index 827e4d3..a6576d4 100644
> --- a/include/asm-generic/fixmap.h
> +++ b/include/asm-generic/fixmap.h
> @@ -28,7 +28,8 @@
> */
> static __always_inline unsigned long fix_to_virt(const unsigned int idx)
> {
> - BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
> + BUILD_BUG_ON(__builtin_constant_p(idx) &&
> + idx >= __end_of_fixed_addresses);
Hmm, this changes the check slightly. Perhaps we should only do this
when your config is active:
{
BUILD_BUG_ON(
/* CONFIG_DEBUG_OPTIMIZE may cause idx not to be constant */
#ifdef CONFIG_DEBUG_OPTIMIZE
__builtin_constant_p(idx) &&
#endif
idx >= __end_of_fixed_addresses);
}
-- Steve
> return __fix_to_virt(idx);
> }
>
