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Fri, 18 Sep 2026 22:45:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Zf51FhK/rWrZBgAAD6G6ig (envelope-from ); Fri, 18 Sep 2026 22:45:38 +0000 From: Fabiano Rosas To: Markus Armbruster Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Subject: Re: [PATCH] qemu-option: Cope with a missing QemuOptsList In-Reply-To: <87wlsmfu1t.fsf@pond.sub.org> References: <20260915134412.4187164-1-farosas@suse.de> <87wlsmfu1t.fsf@pond.sub.org> Date: Fri, 18 Sep 2026 19:45:32 -0300 Message-ID: <87eceqrxf7.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid, suse.de:email, imap1.dmz-prg2.suse.org:helo] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Markus Armbruster writes: > Fabiano Rosas writes: > >> It's a common pattern in vl.c to chain the qemu_find_opts() output >> into the first argument of qemu_opts_parse_noisily(): >> >> opts = qemu_opts_parse_noisily(qemu_find_opts("spice"), optarg, false); >> if (!opts) { >> exit(1); >> } >> >> In cases such as spice that have the group defined in the module file, >> it's possible to reach qemu_opts_parse_noisily() with a NULL QemuOptsList if >> the module is not present in the host filesystem. >> >> $ ../configure --enable-modules --enable-spice >> $ make >> $ mv qemu-bundle/usr/local/lib64/qemu/ui-spice-core.so{,.not} >> $ ./qemu-system-x86_64 -spice a >> qemu-system-x86_64: -spice a: There is no option group 'spice' >> Segmentation fault (core dumped) >> >> Return NULL from qemu_opts_parse_noisily() if there is no list. >> >> Signed-off-by: Fabiano Rosas >> --- >> util/qemu-option.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/util/qemu-option.c b/util/qemu-option.c >> index 9fbf425f86..0ec12d252c 100644 >> --- a/util/qemu-option.c >> +++ b/util/qemu-option.c >> @@ -945,6 +945,10 @@ QemuOpts *qemu_opts_parse_noisily(QemuOptsList *list, const char *params, >> QemuOpts *opts; >> bool help_wanted = false; >> >> + if (!list) { >> + return NULL; >> + } >> + >> opts = opts_parse(list, params, permit_abbrev, true, >> opts_accepts_any(list) ? NULL : &help_wanted, >> &err); > > Before the patch, qemu_opts_parse_noisily() either > > * Succeeds and returns non-null > > * Fails, reports an error, and returns null > > * Prints help and returns null > > Your patch adds a fourth case: > > * Fails silently and returns null > > I dislike this case. Functions should either always print something > whent they fail, or never. > > Are all callers prepared for silent failure? > > The pattern you quoted in the commit message is, because > qemu_find_opts() reports an error. > > Here's a cleaner solution for this pattern. Replace > > opts = qemu_opts_parse_noisily(qemu_find_opts(...), ...) > > by a call of a new helper function that does > > list = qemu_find_opts(...); > if (!list) { > return NULL; > } > return qemu_opts_parse_noisily(list, ...); > > Thoughts? I agree, but I didn't want to add another helper on top of qemu_opts_parse_noisily() so I did some further cleanup, see whether you hate it: https://lore.kernel.org/r/20260918223002.1892021-1-farosas@suse.de