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ctf_arc_import_parent, called by the cached-opening machinery used by
ctf_archive_next and archive-wide lookup functions like
ctf_arc_lookup_symbol, has an err-pointer parameter like all other opening
functions. Unfortunately it unconditionally initializes it whenever
provided, even if there was no error, which can lead to its being
initialized to an uninitialized value. This is not technically an
API-contract violation, since we don't define what happens to the error
value except when an error happens, but it is still unpleasant.
Initialize it only when there is an actual error, so we never initialize it
to an uninitialized value.
While we're at it, improve all the opening pathways: on success, set errp to
0, rather than leaving it what it was, reducing the likelihood of
uninitialized error param returns in callers too. (This is inconsistent
with the treatment of ctf_errno(), but the err value being a parameter
passed in from outside makes the divergence acceptable: in open functions,
you're never going to be overwriting some old error value someone might want
to keep around across multiple calls, some of which are successful and some
of which are not.)
Soup up existing tests to verify all this.
Thanks to Bruce McCulloch for the original patch, and Stephen Brennan for
the report.
libctf/
PR libctf/32903
* ctf-archive.c (ctf_arc_open_internal): Zero errp on success.
(ctf_dict_open_sections): Zero errp at the start.
(ctf_arc_import_parent): Intialize err.
* ctf-open.c (ctf_bufopen): Zero errp at the start.
* testsuite/libctf-lookup/add-to-opened.c: Make sure one-element
archive opens update errp.
* testsuite/libctf-writable/ctf-compressed.c: Make sure real archive
opens update errp.
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Commit 483546ce4f3 ("libctf: make ctf_serialize() actually serialize")
accidentally broke dict compression. There were two bugs:
- ctf_arc_write_one_ctf was still making its own decision about
whether to compress the dict via direct ctf_size comparison, which is
unfortunate because now that it no longer calls ctf_serialize itself,
ctf_size is always zero when it does this: it should let the writing
functions decide on the threshold, which they contain code to do which is
simply not used for lack of one trivial wrapper to write to an fd and
also provide a compression threshold
- ctf_write_mem, the function underlying all writing as of the commit
above, was calling zlib's compressBound and avoiding compression if this
returned a value larger than the input. Unfortunately compressBound does
not do a trial compression and determine whether the result is
compressible: it just adds zlib header sizes to the value passed in, so
our test would *always* have concluded that the value was incompressible!
Avoid by simply always compressing if the raw size is larger than the
threshold: zlib is quite clever enough to avoid actually compressing
if the data is incompressible.
Add a testcase for this.
libctf/
* ctf-impl.h (ctf_write_thresholded): New...
* ctf-serialize.c (ctf_write_thresholded): ... defined here,
a wrapper around...
(ctf_write_mem): ... this. Don't check compressibility.
(ctf_compress_write): Reimplement as a ctf_write_thresholded
wrapper.
(ctf_write): Likewise.
* ctf-archive.c (arc_write_one_ctf): Just call
ctf_write_thresholded rather than trying to work out whether
to compress.
* testsuite/libctf-writable/ctf-compressed.*: New test.
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