Our recent commit to support unnamed structure members better ditched
the old ctf_member_iter iterator body in favour of ctf_member_next.
However, these functions treat unnamed structure members differently:
ctf_member_iter just returned whatever the internal representation
contained, while ctf_member_next took care to always return "" rather
than sometimes returning "" and sometimes NULL depending on whether the
dict was dynamic (a product of ctf_create) or not (a product of
ctf_open). After this commit, ctf_member_iter did the same.
It was always a bug for external callers not to treat a "" return from
these functions as if it were NULL, so only buggy callers could be
affected -- but one of those buggy callers was ctf_add_type, which
assumed that it could just take whatever name was returned from
ctf_member_iter and slam it directly into the internal representation of
a dynamic dict -- which expects NULL for unnamed members, not "". The
net effect of all of this is that taking a struct containing unnamed
members and ctf_add_type'ing it into a dynamic dict produced a dict
whose unnamed members were inaccessible to ctf_member_info (though if
you wrote that dict out and then ctf_open'ed it, they would magically
reappear again).
Compensate for this by suitably transforming a "" name into NULL in the
internal representation, as should have been done all along.
libctf/ChangeLog
2021-01-19 Nick Alcock <nick.alcock@oracle.com>
* ctf-create.c (membadd): Transform ""-named members into
NULL-named ones.
* testsuite/libctf-regression/type-add-unnamed-struct*: New test.
The recent work allowing lookups of pointers in child dicts when the
pointed-to type is in the parent dict broke the case where a pointer
type that does not exist at all is looked up: we mistakenly return the
pointed-to type, which is likely not a pointer at all. This causes
considerable confusion.
Fixed, with a new testcase.
libctf/ChangeLog
2021-01-19 Nick Alcock <nick.alcock@oracle.com>
* ctf-lookup.c (ctf_lookup_by_name_internal): Do not return the
base type if looking up a nonexistent pointer type.
* testsuite/libctf-regression/pptrtab*: Test it.
We never actually check to see if the compiler supports CTF,
or even if a suitable compiler exists.
libctf/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* Makefile.am (BASEDIR): New.
(BFDDIR): Likewise.
(check-DEJAGNU): Add development.exp to prerequisites.
(development.exp): New.
(CONFIG_STATUS_DEPENDENCIES): New.
(EXTRA_DEJAGNU_SITE_CONFIG): Likewise.
(DISTCLEANFILES): Likewise.
* Makefile.in: Regenerated.
* testsuite/lib/ctf-lib.exp (check_ctf_available): Return boolean.
* testsuite/libctf-lookup/lookup.exp: Call check_ctf_available.
* testsuite/libctf-regression/regression.exp: Likewise.
When you look up a type by name using ctf_lookup_by_name, in most cases
libctf can just strip off any qualifiers and look for the name, but for
pointer types this doesn't work, since the caller will want the pointer
type itself. But pointer types are nameless, and while they cite the
types they point to, looking up a type by name requires a link going the
*other way*, from the type pointed to to the pointer type that points to
it.
libctf has always built this up at open time: ctf_ptrtab is an array of
type indexes pointing from the index of every type to the index of the
type that points to it. But because it is built up at open time (and
because it uses type indexes and not type IDs) it is restricted to
working within a single dict and ignoring parent/child
relationships. This is normally invisible, unless you manage to get a
dict with a type in the parent but the only pointer to it in a child.
The ctf_ptrtab will not track this relationship, so lookups of this
pointer type by name will fail. Since which type is in the parent and
which in the child is largely opaque to the user (which goes where is up
to the deduplicator, and it can and does reshuffle things to save
space), this leads to a very bad user experience, with an
obviously-visible pointer type which ctf_lookup_by_name claims doesn't
exist.
The fix is to have another array, ctf_pptrtab, which is populated in
child dicts: like the parent's ctf_ptrtab, it has one element per type
in the parent, but is all zeroes except for those types which are
pointed to by types in the child: so it maps parent dict indices to
child dict indices. The array is grown, and new child types scanned,
whenever a lookup happens and new types have been added to the child
since the last time a lookup happened that might need the pptrtab.
(So for non-writable dicts, this only happens once, since new types
cannot be added to non-writable dicts at all.)
Since this introduces new complexity (involving updating only part of
the ctf_pptrtab) which is only seen when a writable dict is in use, we
introduce a new libctf-writable testsuite that contains lookup tests
with no corresponding CTF-containing .c files (which can thus be run
even on platforms with no .ctf-section support in the linker yet), and
add a test to check that creation of pointers in children to types in
parents and a following lookup by name works as expected. The non-
writable case is tested in a new libctf-regression testsuite which is
used to track now-fixed outright bugs in libctf.
libctf/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dict_t) <ctf_pptrtab>: New.
<ctf_pptrtab_len>: New.
<ctf_pptrtab_typemax>: New.
* ctf-create.c (ctf_serialize): Update accordingly.
(ctf_add_reftype): Note that we don't need to update pptrtab here,
despite updating ptrtab.
* ctf-open.c (ctf_dict_close): Destroy the pptrtab.
(ctf_import): Likewise.
(ctf_import_unref): Likewise.
* ctf-lookup.c (grow_pptrtab): New.
(refresh_pptrtab): New, update a pptrtab.
(ctf_lookup_by_name): Turn into a wrapper around (and rename to)...
(ctf_lookup_by_name_internal): ... this: construct the pptrtab, and
use it in addition to the parent's ptrtab when parent dicts are
searched.
* testsuite/libctf-regression/regression.exp: New testsuite for
regression tests.
* testsuite/libctf-regression/pptrtab*: New test.
* testsuite/libctf-writable/writable.exp: New testsuite for tests of
writable CTF dicts.
* testsuite/libctf-writable/pptrtab*: New test.
