[libvirt] [PATCH 00/21] tests: qemuxml2argv: support optional arguments

[Cole Robinson]

On 3/14/19 11:17 AM, Eric Blake wrote:
> On 3/14/19 9:43 AM, Cole Robinson wrote:
>> Right now in qemuxml2argv we have a proliferation of DO_*TEST* macros.
>> They essentially fill in data in the testInfo struct and invoke the
>> test function.
>>
>> There's several bits of data that we want to specify for a small
>> subset of tests: flags, parseFlags, migrateFrom/migrateFd, gic. The
>> base macros need to handle these in their argument lists, and we
>> provide many convenience macros that fill in default values for the
>> less common parameters. Any time we want to add a new bit of data
>> though, the base macros are extended, and every caller of those
>> needs to be adjusted, and we are faced with the question of whether
>> to extend the combinatorial explosion of convenience macros which
>> have only a subset of options exposed.
>>
>> This series adds a testInfoSetArgs which uses va_args to make these
>> mandatory parameters optional. The general format is:
>>
>>      DO_TEST_FULL(...
>>                   ARG_FOO, foovalue,
>>                   ARG_BAR, barvalue, ...)
>>
>> Specifically, one of the migrate tests went from:
>>
>>      DO_TEST_FULL("restore-v2", "exec:cat", 7, 0, 0, GIC_NONE, NONE);
>>
>> to:
>>
>>      DO_TEST_FULL("restore-v2",
>>                   ARG_MIGRATE_FROM, "exec:cat",
>>                   ARG_MIGRATE_FD, 7,
>>                   ARG_QEMU_CAPS, NONE);
> 
> Umm, what's your sentinel value here? It is undefined behavior to call
> va_arg more times than there are arguments present, but without some
> sort of sentinel, you don't know when to stop calling va_arg.
> 
> The overall idea is nice, but I think you need an ARG_END sentinel.
> 

You saw it in the later patches, but just to respond here if anyone else 
is watching: there is an ARG_END but it's hidden in the macro definitions.

- Cole

- Cole