Re: [libvirt] [PATCH] Rewrite the way mockable functions are handled.

On Wed, Jul 12, 2017 at 05:06:22PM +0100, Daniel P. Berrange wrote: > Currently any mockable functions are marked with attributes > noinline, noclone and weak. This prevents the compiler from > optimizing away the impl of these functions. > > It has an unfortunate side effect with the libtool convenience > libraries, if executables directly link to them. For example > virlockd, virlogd both link to libvirt_util.la When this is > done, the linker does not consider weak symbols as being > undefined, so it never copies them into the final executable. > > In this new approach, we stop annotating the headers entirely. > Instead we create a weak function alias in the source. > > int fooImpl(void) { > ..the real code.. > } > > int foo(void) __attribute__((noinline, noclone, weak, alias("fooImpl")) > > If any functions in the same file call "foo", this prevents the > optimizer from inlining any part of fooImpl. When linking to the > libtool convenience static library, we also get all the symbols > present. Finally the test suite can just directly define a > 'foo' function in its source, removing the need to use LD_PRELOAD > (though removal of LD_PRELOADS is left for a future patch). > What are you using for tag navigation? With this macro-defined functions I cannot easily jump to them (the main reason why I don't like macros defining functions).

I would very much prefer if ATTRIBUTE_MOCKABLE just took a parameter like this: #define ATTRIBUTE_MOCKABLE(func) __attribute__((noinline, noclone, weak, alias(#func "Impl")) (written by hand, don't take mu word for it working out of the box) and the original function would be left untouched.

Also, this fails on OS X [1] and I don't really see why: util/vircommand.c:988:1: error: only weak aliases are supported on darwin VIR_MOCKABLE(void, ^ ./internal.h:252:60: note: expanded from macro 'VIR_MOCKABLE' ret name(__VA_ARGS__) __attribute__((noinline, weak, __alias__(#name "Impl"))); \