Re: [libvirt] [PATCH 2/2] Add some DTrace/SystemTAP probes to the RPC code

From: "Daniel P. Berrange"<berrange(a)redhat.com>

+ +/* Systemtap 1.2 headers have a bug where they cannot handle a + * variable declared with array type. Work around this by casting all + * arguments. This is some gross use of the preprocessor because + * PROBE is a var-arg macro, but it is better than the alternative of + * making all callers to PROBE have to be aware of the issues. And + * hopefully, if we ever add a call to PROBE with other than 2 or 3

+ * end arguments, you can figure out the pattern to extend this hack. + */ +# define VIR_COUNT_ARGS(...) VIR_ARG9(__VA_ARGS__, 8, 7, 6, 5, 4, 3, 2, 1) +# define VIR_ARG9(_1, _2, _3, _4, _5, _6, _7, _8, _9, ...) _9 +# define VIR_ADD_CAST_EXPAND(a, b, ...) VIR_ADD_CAST_PASTE(a, b, __VA_ARGS__) +# define VIR_ADD_CAST_PASTE(a, b, ...) a##b(__VA_ARGS__) + +/* The double cast is necessary to silence gcc warnings; any pointer + * can safely go to intptr_t and back to void *, which collapses + * arrays into pointers; while any integer can be widened to intptr_t + * then cast to void *. */ +# define VIR_ADD_CAST(a) ((void *)(intptr_t)(a))

+# define VIR_ADD_CAST2(a, b) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b) +# define VIR_ADD_CAST3(a, b, c) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c) +# define VIR_ADD_CAST4(a, b, c, d) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d) +# define VIR_ADD_CAST5(a, b, c, d, e) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d), VIR_ADD_CAST(e) +# define VIR_ADD_CAST6(a, b, c, d, e, f) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d), VIR_ADD_CAST(e), VIR_ADD_CAST(f) +# define VIR_ADD_CAST7(a, b, c, d, e, f, g) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d), VIR_ADD_CAST(e), VIR_ADD_CAST(f), \ + VIR_ADD_CAST(g)

+# define VIR_ADD_CAST8(a, b, c, d, e, f, g, h) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d), VIR_ADD_CAST(e), VIR_ADD_CAST(f), \ + VIR_ADD_CAST(g), VIR_ADD_CAST(h) +# define VIR_ADD_CAST9(a, b, c, d, e, f, g, h, i) \ + VIR_ADD_CAST(a), VIR_ADD_CAST(b), VIR_ADD_CAST(c), \ + VIR_ADD_CAST(d), VIR_ADD_CAST(e), VIR_ADD_CAST(f), \ + VIR_ADD_CAST(g), VIR_ADD_CAST(h), VIR_ADD_CAST(i)