[LTP] [RFC PATCH 1/8] lib: Fix linking error multiple TCID definitions with -fno-common

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> > > +extern const char *TCID;
> 
> > Do we really need this extern or can we remove it?
> Some code is using TCID, not sure if it could be replaced by something else or
> whether is worth to add API function which returns TCID.
> 
> In file included from memfd_create01.c:17:
> memfd_create01.c: In function ???verify_memfd_create???:
> memfd_create01.c:244:21: error: ???TCID??? undeclared (first use in this function)
>   244 |  fd = CHECK_MFD_NEW(TCID, MFD_DEF_SIZE, tc->flags);
>       |                     ^~~~
> ---

This one is used as a unique test identifier, we can hardcode something
as "ltp_memfd_create01" there instead.

> 
> In file included from testcases/kernel/mem/include/mem.h:4,
>                  from overcommit_memory.c:72:
> overcommit_memory.c: In function ???setup???:
> overcommit_memory.c:105:33: error: ???TCID??? undeclared (first use in this function)
>   105 |     "can't support to test %s", TCID);
>       |                                 ^~~~
> ---
> 
> In file included from ima_mmap.c:9:
> ima_mmap.c: In function ???run???:
> ima_mmap.c:36:43: error: ???TCID??? undeclared (first use in this function)
>    36 |   tst_brk(TBROK, "Usage: %s -f filename", TCID);
>       |                                           ^~~~

Hmm these two are using the TCID as a test binary name, which kind of
works by accident. Because:

1. The library uses argv[0] to initialize TCID
2. Then TCID is used as a prefix for the temporary directory
   the test has created and also for filename on tmpfs

There is no guarantee that TCID is equal to argv[0], it's only supposed
to be unique identifier for a test.

So I would rather be for removing TCID from these tests. The question is
if we want to replace it with something that is guaranteed to contain
the test binary name or remove it completely.

-- 
chrubis@suse.cz