Re: [PATCH v6 05/11] qapi: introduce QAPISchemaIfCond.cgen()

[Markus Armbruster]

Markus Armbruster <armbru@redhat.com> writes:

> marcandre.lureau@redhat.com writes:
>
>> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>>
>> Instead of building prepocessor conditions from a list of string, use
>> the result generated from QAPISchemaIfCond.cgen() and hide the
>> implementation details.
>>
>> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Please mention that the patch changes generated code.  See below for
> details.

[...]

> This patch does three things:
>
> (1) Change gen_if(), gen_endif() to always generate a single #if,
>     #endif.  This enables:
>
> (2) Factor cgen_ifcond() out of gen_if() and gen_endif()
>
> (3) Lift the call of cgen_ifcond() into into gen_if()'s, gen_endif()'s
>     callers.
>
> I'd split the patch.  This is *not* a demand.
>
> The motivation for (3) is unclear.  Is it so gen_if() doesn't depend on
> QAPISchemaIfCond?
>
> Step (1) affects the generated code.  When @ifcond is [COND1, COND2, ...],
> gen_if()'s value changes from
>
>     #if COND1
>     #if COND2
>     ...
>
> to
>
>     #if (COND1) && (COND2)

[...]

> The common case: when it's just [COND], the value changes from
>
>     #if COND
>
> to
>
>     #if (COND)
>
> which is a bit ugly.
>
> Example: in qapi-types-block-export.c

[...]

> Avoiding the redundant pair of parenthesis takes another special case.
> Let's do it.

Looks like PATCH 07 does it.  Avoiding the temporary change would be
nice, but isn't required.