Hi all,
In the context of violations of MISRA C:2012 Rule 17.7: "The value
returned by a function having non-void return type shall be used", I was
looking at the function "clean_and_invalidate_dcache_va_range". It has
the following signature on both arm and x86:
static inline int clean_and_invalidate_dcache_va_range
(const void *p, unsigned long size)
The commit that introduced it for Arm ~9 years ago (71d64afe3e12: "arm:
return int from *_dcache_va_range") [1] mentions that on Arm it can't
fail, but supposedly it can on x86.
However, as far as I can tell, for both arch-es the implementation now
always returns 0 [2][3], so perhaps the mention of -EOPNOTSUPP for x86
is no longer true (I wasn't able to reconstruct if there was a time at
which this was true, even in the same commit that changed the return
type to int).
The question is: should the return type be void, since it appears that
every user is ignoring the returned value (violating the rule), except
the one in common/grant_table.c [4]?
The other two resolution paths are either allowing this function's
result to be ignored or cast all ignored invocations to void, with the
first being cleaner from a code readability perspective.
[1] These functions cannot really fail on ARM, but their x86 equivalents
can (-EOPNOTSUPP). Change the prototype to return int.
[2]
https://gitlab.com/xen-project/xen/-/blob/staging/xen/arch/arm/include/asm/page.h#L218
[3]
https://gitlab.com/xen-project/xen/-/blob/staging/xen/arch/x86/include/asm/flushtlb.h#L188
[4]
https://gitlab.com/xen-project/xen/-/blob/staging/xen/common/grant_table.c#L3576
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)
