On Dienstag, 1. Februar 2022 11:11:37 CET Greg Kurz wrote: > On Mon, 31 Jan 2022 18:43:22 +0100 > > Christian Schoenebeck <[email protected]> wrote: > > On Montag, 31. Januar 2022 17:39:30 CET Greg Kurz wrote: > > > It is recommended to use g_autofree or g_autoptr as it reduces > > > the odds of introducing memory leaks in future changes. Let's do > > > that everywhere a glib allocation is performed. > > > > > > The virtio_9p_create_local_test_dir() function needs some extra > > > care though : the template pointer is eventually cached into the > > > local_test_path global variable for the duration of the tests and > > > should not be freed. Add the g_autofree annotation but negate it > > > with g_steal_pointer() to make it clear that the pointer ownership > > > is dropped on purpose. > > > > > > Based-on: > > > <f6602123c6f7d0d593466231b04fba087817abbd.1642879848.git.qemu_oss@crudeb > > > yte > > > .com> Signed-off-by: Greg Kurz <[email protected]> > > > --- > > > v2: - fix crash with local_test_path > > > --- > > > > > > tests/qtest/libqos/virtio-9p.c | 30 +++++++++++++++--------------- > > > 1 file changed, 15 insertions(+), 15 deletions(-) > > > > > > diff --git a/tests/qtest/libqos/virtio-9p.c > > > b/tests/qtest/libqos/virtio-9p.c index ef96ef006adc..f0ffbc583492 > > > 100644 > > > --- a/tests/qtest/libqos/virtio-9p.c > > > +++ b/tests/qtest/libqos/virtio-9p.c > > > @@ -37,18 +37,22 @@ static char *concat_path(const char* a, const char* > > > b) > > > > > > return g_build_filename(a, b, NULL); > > > > > > } > > > > > > -void virtio_9p_create_local_test_dir(void) > > > +static char *make_temp_dir(char *template) > > > > > > { > > > > > > - struct stat st; > > > - char *pwd = g_get_current_dir(); > > > - char *template = concat_path(pwd, "qtest-9p-local-XXXXXX"); > > > - > > > - local_test_path = mkdtemp(template); > > > - if (!local_test_path) { > > > + char *path = mkdtemp(template); > > > + if (!path) { > > > > > > g_test_message("mkdtemp('%s') failed: %s", template, > > > > > > strerror(errno)); } > > > - g_free(pwd); > > > + return path; > > > +} > > > + > > > +void virtio_9p_create_local_test_dir(void) > > > +{ > > > + g_autofree char *pwd = g_get_current_dir(); > > > + g_autofree char *template = concat_path(pwd, > > > "qtest-9p-local-XXXXXX"); > > > + struct stat st; > > > > > > + local_test_path = make_temp_dir(g_steal_pointer(&template)); > > > > Quite noisy diff and under the bottom line, it does not fix what it > > originally supposed to: addressing the leak of the global variable > > 'local_test_path'. g_steal_pointer() simply makes the previous g_autofree > > prefix pointless. > The g_autofree and g_steal_pointer() dance is just an idiom that > says "I'm not freeing this pointer on purpose, it will be handled > somewhere else". No big deal. I'll split this in two patches : one > for the leak of 'local_test_path' with a clear comment instead of > g_autofree and one for the remaining g_auto* conversions.
Yeah, I got that, but it still adds redundant code, as if adding a constant literal expression like "... * 1/2 * 2". The other changes have an actual purpose: they reduce code. This one though just adds noise without a real purpose, plus it reverts of what I just have done with the previous patch: getting rid of the previously already existing separate function init_local_test_path(): https://github.com/cschoenebeck/qemu/commit/072636e2a9f3a153078e6046e52ae5a330728b68 I don't care enough though to continue defending my position on this. > > Why not just moving g_autofree from 'template' to the global variable > > 'local_test_path' and avoid all that noise? > > Because the 'cleanup' attribute cannot be set on a static variable as > documented in GCC: > > cleanup (cleanup_function) > > The cleanup attribute runs a function when the variable goes out of > scope. This attribute can only be applied to auto function scope > variables; it may not be applied to parameters or variables with > static storage duration. The function must take one parameter, a > pointer to a type compatible with the variable. The return value > of the function (if any) is ignored. > > and trying to do so produces: > > ../../tests/qtest/libqos/virtio-9p.c:32:1: error: ‘cleanup’ attribute > ignored [-Werror=attributes] 32 | static g_autofree char *local_test_path; > > | ^~~~~~ > > cc1: all warnings being treated as errors > > The leak of 'local_test_path' can only be addressed with a g_free() > in its last user, i.e. virtio_9p_remove_local_test_dir(). Agreed, that would probably be the best solution for now. Thanks! Best regards, Christian Schoenebeck
