Re: Add LZ4 compression in pg_dump

------- Original Message -------
On Friday, May 5th, 2023 at 8:00 AM, Alexander Lakhin <exclusion(at)gmail(dot)com> wrote:

>
>
> 23.03.2023 20:10, Tomas Vondra wrote:
>
> > So pushed all three parts, after updating the commit messages a bit.
> >
> > This leaves the empty-data issue (which we have a fix for) and the
> > switch to LZ4F. And then the zstd part.
>
>
> I'm sorry that I haven't noticed/checked that before, but when trying to
> perform check-world with Valgrind I've discovered another issue presumably
> related to LZ4File_gets().
> When running under Valgrind:
> PROVE_TESTS=t/002_pg_dump.pl make check -C src/bin/pg_dump/
> I get:
> ...
> 07:07:11.683 ok 1939 - compression_lz4_dir: glob check for
> .../src/bin/pg_dump/tmp_check/tmp_test_HB6A/compression_lz4_dir/*.dat.lz4
> # Running: pg_restore --jobs=2 --file=.../src/bin/pg_dump/tmp_check/tmp_test_HB6A/compression_lz4_dir.sql
> .../src/bin/pg_dump/tmp_check/tmp_test_HB6A/compression_lz4_dir
>
> ==00:00:00:00.579 2811926== Conditional jump or move depends on uninitialised value(s)
> ==00:00:00:00.579 2811926== at 0x4853376: rawmemchr (vg_replace_strmem.c:1548)
> ==00:00:00:00.579 2811926== by 0x4C96A67: _IO_str_init_static_internal (strops.c:41)
> ==00:00:00:00.579 2811926== by 0x4C693A2: _IO_strfile_read (strfile.h:95)
> ==00:00:00:00.579 2811926== by 0x4C693A2: __isoc99_sscanf (isoc99_sscanf.c:28)
> ==00:00:00:00.579 2811926== by 0x11DB6F: _LoadLOs (pg_backup_directory.c:458)
> ==00:00:00:00.579 2811926== by 0x11DD1E: _PrintTocData (pg_backup_directory.c:422)
> ==00:00:00:00.579 2811926== by 0x118484: restore_toc_entry (pg_backup_archiver.c:882)
> ==00:00:00:00.579 2811926== by 0x1190CC: RestoreArchive (pg_backup_archiver.c:699)
> ==00:00:00:00.579 2811926== by 0x10F25D: main (pg_restore.c:414)
> ==00:00:00:00.579 2811926==
> ...
>
> It looks like the line variable returned by gets_func() here is not
> null-terminated:
> while ((CFH->gets_func(line, MAXPGPATH, CFH)) != NULL)
>
> {
> ...
> if (sscanf(line, "%u %" CppAsString2(MAXPGPATH) "s\n", &oid, lofname) != 2)
> ...
> And Valgrind doesn't like it.
>

Valgrind is correct to not like it. LZ4Stream_gets() got modeled after
gets() when it should have been modeled after fgets().

Please find a patch attached to address it.

Cheers,
//Georgios

> Best regards,
> Alexander