| Message ID | 20220131163930.61521-1-groug@kaod.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] tests/9pfs: Use g_autofree and g_autoptr where possible | expand |
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@crudebyte > .com> Signed-off-by: Greg Kurz <groug@kaod.org> > --- > 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. Why not just moving g_autofree from 'template' to the global variable 'local_test_path' and avoid all that noise? > g_assert(local_test_path != NULL); > > /* ensure test directory exists now ... */ > @@ -60,12 +64,11 @@ void virtio_9p_create_local_test_dir(void) > void virtio_9p_remove_local_test_dir(void) > { > g_assert(local_test_path != NULL); > - char *cmd = g_strdup_printf("rm -fr '%s'\n", local_test_path); > + g_autofree char *cmd = g_strdup_printf("rm -fr '%s'\n", > local_test_path); int res = system(cmd); > if (res < 0) { > /* ignore error, dummy check to prevent compiler error */ > } > - g_free(cmd); > } > > char *virtio_9p_test_path(const char *path) > @@ -209,8 +212,8 @@ static void *virtio_9p_pci_create(void *pci_bus, > QGuestAllocator *t_alloc, static void regex_replace(GString *haystack, > const char *pattern, const char *replace_fmt, ...) > { > - GRegex *regex; > - char *replace, *s; > + g_autoptr(GRegex) regex = NULL; > + g_autofree char *replace = NULL, *s = NULL; > va_list argp; > > va_start(argp, replace_fmt); > @@ -220,9 +223,6 @@ static void regex_replace(GString *haystack, const char > *pattern, regex = g_regex_new(pattern, 0, 0, NULL); > s = g_regex_replace(regex, haystack->str, -1, 0, replace, 0, NULL); > g_string_assign(haystack, s); > - g_free(s); > - g_regex_unref(regex); > - g_free(replace); > } > > void virtio_9p_assign_local_driver(GString *cmd_line, const char *args)
On Mon, 31 Jan 2022 18:43:22 +0100 Christian Schoenebeck <qemu_oss@crudebyte.com> 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@crudebyte > > .com> Signed-off-by: Greg Kurz <groug@kaod.org> > > --- > > 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. > 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(). > > g_assert(local_test_path != NULL); > > > > /* ensure test directory exists now ... */ > > @@ -60,12 +64,11 @@ void virtio_9p_create_local_test_dir(void) > > void virtio_9p_remove_local_test_dir(void) > > { > > g_assert(local_test_path != NULL); > > - char *cmd = g_strdup_printf("rm -fr '%s'\n", local_test_path); > > + g_autofree char *cmd = g_strdup_printf("rm -fr '%s'\n", > > local_test_path); int res = system(cmd); > > if (res < 0) { > > /* ignore error, dummy check to prevent compiler error */ > > } > > - g_free(cmd); > > } > > > > char *virtio_9p_test_path(const char *path) > > @@ -209,8 +212,8 @@ static void *virtio_9p_pci_create(void *pci_bus, > > QGuestAllocator *t_alloc, static void regex_replace(GString *haystack, > > const char *pattern, const char *replace_fmt, ...) > > { > > - GRegex *regex; > > - char *replace, *s; > > + g_autoptr(GRegex) regex = NULL; > > + g_autofree char *replace = NULL, *s = NULL; > > va_list argp; > > > > va_start(argp, replace_fmt); > > @@ -220,9 +223,6 @@ static void regex_replace(GString *haystack, const char > > *pattern, regex = g_regex_new(pattern, 0, 0, NULL); > > s = g_regex_replace(regex, haystack->str, -1, 0, replace, 0, NULL); > > g_string_assign(haystack, s); > > - g_free(s); > > - g_regex_unref(regex); > > - g_free(replace); > > } > > > > void virtio_9p_assign_local_driver(GString *cmd_line, const char *args) > >
On Dienstag, 1. Februar 2022 11:11:37 CET Greg Kurz wrote: > On Mon, 31 Jan 2022 18:43:22 +0100 > > Christian Schoenebeck <qemu_oss@crudebyte.com> 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 <groug@kaod.org> > > > --- > > > 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
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)); g_assert(local_test_path != NULL); /* ensure test directory exists now ... */ @@ -60,12 +64,11 @@ void virtio_9p_create_local_test_dir(void) void virtio_9p_remove_local_test_dir(void) { g_assert(local_test_path != NULL); - char *cmd = g_strdup_printf("rm -fr '%s'\n", local_test_path); + g_autofree char *cmd = g_strdup_printf("rm -fr '%s'\n", local_test_path); int res = system(cmd); if (res < 0) { /* ignore error, dummy check to prevent compiler error */ } - g_free(cmd); } char *virtio_9p_test_path(const char *path) @@ -209,8 +212,8 @@ static void *virtio_9p_pci_create(void *pci_bus, QGuestAllocator *t_alloc, static void regex_replace(GString *haystack, const char *pattern, const char *replace_fmt, ...) { - GRegex *regex; - char *replace, *s; + g_autoptr(GRegex) regex = NULL; + g_autofree char *replace = NULL, *s = NULL; va_list argp; va_start(argp, replace_fmt); @@ -220,9 +223,6 @@ static void regex_replace(GString *haystack, const char *pattern, regex = g_regex_new(pattern, 0, 0, NULL); s = g_regex_replace(regex, haystack->str, -1, 0, replace, 0, NULL); g_string_assign(haystack, s); - g_free(s); - g_regex_unref(regex); - g_free(replace); } void virtio_9p_assign_local_driver(GString *cmd_line, const char *args)
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@crudebyte.com> Signed-off-by: Greg Kurz <groug@kaod.org> --- v2: - fix crash with local_test_path --- tests/qtest/libqos/virtio-9p.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-)