mirror_zfs/lib
Richard Yao 6a42939fcd
Cleanup: Address Clang's static analyzer's unused code complaints
These were categorized as the following:

 * Dead assignment		23
 * Dead increment		4
 * Dead initialization		6
 * Dead nested assignment	18

Most of these are harmless, but since actual issues can hide among them,
we correct them.

That said, there were a few return values that were being ignored that
appeared to merit some correction:

 * `destroy_callback()` in `cmd/zfs/zfs_main.c` ignored the error from
   `destroy_batched()`. We handle it by returning -1 if there is an
   error.

 * `zfs_do_upgrade()` in `cmd/zfs/zfs_main.c` ignored the error from
   `zfs_for_each()`. We handle it by doing a binary OR of the error
   value from the subsequent `zfs_for_each()` call to the existing
   value. This is how errors are mostly handled inside `zfs_for_each()`.
   The error value here is passed to exit from the zfs command, so doing
   a binary or on it is better than what we did previously.

 * `get_zap_prop()` in `module/zfs/zcp_get.c` ignored the error from
   `dsl_prop_get_ds()` when the property is not of type string. We
   return an error when it does. There is a small concern that the
   `zfs_get_temporary_prop()` call would handle things, but in the case
   that it does not, we would be pushing an uninitialized numval onto
   the lua stack. It is expected that `dsl_prop_get_ds()` will succeed
   anytime that `zfs_get_temporary_prop()` does, so that not giving it a
   chance to fix things is not a problem.

 * `draid_merge_impl()` in `tests/zfs-tests/cmd/draid.c` used
   `nvlist_add_nvlist()` twice in ways in which errors are expected to
   be impossible, so we switch to `fnvlist_add_nvlist()`.

A few notable ones did not merit use of the return value, so we
suppressed it with `(void)`:

 * `write_free_diffs()` in `lib/libzfs/libzfs_diff.c` ignored the error
   value from `describe_free()`. A look through the commit history
   revealed that this was intentional.

 * `arc_evict_hdr()` in `module/zfs/arc.c` did not need to use the
   returned handle from `arc_hdr_realloc()` because it is already
   referenced in lists.

 * `spa_vdev_detach()` in `module/zfs/spa.c` has a comment explicitly
   saying not to use the error from `vdev_label_init()` because whatever
   causes the error could be the reason why a detach is being done.

Unfortunately, I am not presently able to analyze the kernel modules
with Clang's static analyzer, so I could have missed some cases of this.
In cases where reports were present in code that is duplicated between
Linux and FreeBSD, I made a conscious effort to fix the FreeBSD version
too.

After this commit is merged, regressions like dee8934 should become
extremely obvious with Clang's static analyzer since a regression would
appear in the results as the only instance of unused code. That assumes
that Coverity does not catch the issue first.

My local branch with fixes from all of my outstanding non-draft pull
requests shows 118 reports from Clang's static anlayzer after this
patch. That is down by 51 from 169.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Cedric Berger <cedric@precidata.com>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13986
2022-10-14 13:37:54 -07:00
..
libavl cppcheck: explicitly exclude kernel code from userspace checks 2022-05-10 10:20:55 -07:00
libefi Cleanup: Address Clang's static analyzer's unused code complaints 2022-10-14 13:37:54 -07:00
libicp Introduce BLAKE3 checksums as an OpenZFS feature 2022-06-08 15:55:57 -07:00
libnvpair Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
libshare Fix unsafe string operations 2022-09-27 16:47:24 -07:00
libspl Reduce false positives from Static Analyzers 2022-09-30 15:30:12 -07:00
libtpool Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
libunicode cppcheck: explicitly exclude kernel code from userspace checks 2022-05-10 10:20:55 -07:00
libuutil Cleanup: Remove unused uu_pname code 2022-09-19 17:33:52 -07:00
libzfs Cleanup: Address Clang's static analyzer's unused code complaints 2022-10-14 13:37:54 -07:00
libzfs_core Fix potential NULL pointer dereference in lzc_ioctl() 2022-10-14 13:33:22 -07:00
libzfsbootenv Fix unchecked return values and unused return values 2022-09-23 16:52:03 -07:00
libzpool Fix memory leak found by GCC static analyzer 2022-10-03 13:41:58 -07:00
libzstd cppcheck: explicitly exclude kernel code from userspace checks 2022-05-10 10:20:55 -07:00
libzutil Cleanup: Address Clang's static analyzer's unused code complaints 2022-10-14 13:37:54 -07:00
Makefile.am autoconf: use include directives instead of recursing down lib 2022-05-10 10:18:11 -07:00