Date: Fri, 27 Jul 2012 11:38:24 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: current@freebsd.org Subject: (void)foo or __unused foo ? Message-ID: <20120727093824.GB56662@onelab2.iet.unipi.it>
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In writing cross platform code I often have to deal with function arguments or variables that are not used on certain platforms. In FreeBSD:sys/cdefs.h we have #define __unused __attribute__((__unused__)) and in the kernel we tend to annotate with "__unused" such arguments int f(type foo __unused) However on linux __unused is not a standard macro, and is often used as a variable or field name in standard headers, so introducing our __unused macro breaks compilation there. The alternative way to avoid an 'unused' warning from the compiler is an empty statement (void)foo; that the compiler hopefully optimizes away. Any disadvantage or objection to selectively use this form in our kernel code for parts that need to work on multiple platforms ? cheers luigi
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