[LTP] [PATCH 1/2] ptrace07: Fix compilation when not on x86

[Martin Doucha]

On 20. 10. 22 5:53, Li Wang wrote:
> 
> 
> On Wed, Oct 19, 2022 at 5:30 PM Martin Doucha <mdoucha@suse.cz 
> <mailto:mdoucha@suse.cz>> wrote:
>     Reverting 1df4de06206b079f24dde7157d037b48727c743d is the best solution
>     here. Building ptrace07 and similar arch-specific tests without a key
>     piece of code does not make sense. The preprocessor arch checks should
>     wrap around the whole file, not just a small non-portable bit that's
>     crucial for the test to work.
> 
>  From what I know, one of the uses of "empty macro" is to conditionally
> include certain portions of a program. In ptrace07, it invokes that useless
> macro for compiling pass on non-x86 arch but does not allow execute it.
> 
> I don't see why that's crucial for a test, if we wrap around the whole 
> file and
> avoid it compiling on non-x86, isn't this essentially same as that?
> 
> The only distinction between them is partly or wholly skipping the key
> code compilation. or maybe I completely misunderstood this part.

The code that would be generated by the non-empty version of the macro 
is crucial for rest of the program to work. Putting conditional build 
directives only around a few lines of code can cause bogus warnings 
about uninitialized variables and make it difficult to add more 
arch-specific code like the cpuid_count() macro. There's nothing wrong 
with writing tests like this:

#include "tst_test.h"

#ifdef __x86_64__
#include "lapi/cpuid.h"

void setup(void)
{
	...
}

void run(void)
{
	...
}

void cleanup(void)
{
	...
}

static struct tst_test test = {
	...
	.supported_archs = (const char *const []) {
		"x86_64",
		NULL
	},
};

#else /* __x86_64__ */
#define TST_TEST_TCONF("this test is only supported on x86_64")
#endif /* __x86_64__ */


IIUC, the metadata parser will still read .supported_archs regardless of 
conditional build directives. And it'll prevent erratic test behavior in 
edge cases where the LTP library believes the code was compiled for the 
right architecture but the GCC preprocessor disagrees.

-- 
Martin Doucha   mdoucha@suse.cz
QA Engineer for Software Maintenance
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic