Currently, if we want to mock a function the noinline attribute
is appended after the function (via G_NO_INLINE macro). This used
to work for non pure functions. But there are some trivial
functions (for instance virQEMUCapsProbeHVF()) that are pure,
i.e. have no side effect, and while their call from other parts
of the code is not optimized out, their call from within the same
compilation unit (qemu_capabilities.c) is optimized out.
This is because inlining and semantic interposition are two
different things. Even GCC's documentation for noinline attribute
[1] states that clearly:
This function attribute prevents a function from being
considered for inlining. It also disables some other
interprocedural optimizations; it’s preferable to use the more
comprehensive noipa attribute instead if that is your goal.
Even if a function is declared with the noinline attribute,
there are optimizations other than inlining that can cause
calls to be optimized away if it does not have side effects,
although the function call is live.
Unfortunately, despite attempts [2] Clang still does not support
the attribute and thus we have to rely on noinline +
-fsemantic-interposition combo.
1: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
2: https://reviews.llvm.org/D101011
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
While being great semantic patching tool, coccinelle fails to
understand some of macros we use (including those provided by
glib). What they have in common is use of __attribute__ under the
hood. We store a list of such macros in a file. But in there,
g_auto() macro is not defined properly. Indeed, g_auto(type)
declares a local variable of given type, for instance from
cocci's POV:
g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
virBuffer buf = VIR_BUFFER_INITIALIZER;
are both the same declaration. Fix declaration of g_auto() stub.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Tim Wiederhake <twiederh@redhat.com>
Michal Privoznik
Ján Tomko