| Message ID | 20210128065010.218830-1-sunke32@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | src/swapon.c: initiate p to NULL | expand |
On Thu, Jan 28, 2021 at 02:50:10PM +0800, Sun Ke wrote: > when run make, show: > swapon.c:135:3: warning: 'p' may be used uninitialized in this function > [-Wmaybe-uninitialized] > memcpy(p, buf, BUF_SIZE); > ^~~~~~~~~~~~~~~~~~~~~~~~ > fix it. If you don't have a situation to prove this's a real bug, I guess the gcc might think the 'p' can be used uninitialized at here when verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: memcpy(p, buf, BUF_SIZE); break; But from the code logic, if verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER, the 'p' will be initialized by: switch (verb) { case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: case TEST_MWRITE_BEFORE: p = mmap(NULL, BUF_SIZE, PROT_WRITE | PROT_READ, MAP_SHARED, So I think this's a fake uninitialized warning (Maybe I'm wrong. But if I'm right, better to specify that in commit log). Anyway, I personally don't object to initialize a pointer to NULL at beginning, and make a build warning disappear. Leave the decision to maintainer :) Thanks, Zorro > > Signed-off-by: Sun Ke <sunke32@huawei.com> > --- > src/swapon.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/src/swapon.c b/src/swapon.c > index afaed405..fe8949a3 100644 > --- a/src/swapon.c > +++ b/src/swapon.c > @@ -41,7 +41,7 @@ int main(int argc, char **argv) > .sa_handler = handle_signal, > }; > enum verbs verb = TEST_SWAPON; > - void *p; > + void *p = NULL; > ssize_t sz; > int fd = -1; > int ret, c; > -- > 2.13.6 >
hi Zorro 在 2021/1/30 12:58, Zorro Lang 写道: > On Thu, Jan 28, 2021 at 02:50:10PM +0800, Sun Ke wrote: >> when run make, show: >> swapon.c:135:3: warning: 'p' may be used uninitialized in this function >> [-Wmaybe-uninitialized] >> memcpy(p, buf, BUF_SIZE); >> ^~~~~~~~~~~~~~~~~~~~~~~~ >> fix it. > If you don't have a situation to prove this's a real bug, I guess the gcc might > think the 'p' can be used uninitialized at here when verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: > > case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: > memcpy(p, buf, BUF_SIZE); > break; > > But from the code logic, if verb is TEST_MWRITE_BEFORE_AND_MWRITE_AFTER, the 'p' > will be initialized by: > > switch (verb) { > case TEST_MWRITE_BEFORE_AND_MWRITE_AFTER: > case TEST_MWRITE_BEFORE: > p = mmap(NULL, BUF_SIZE, PROT_WRITE | PROT_READ, MAP_SHARED, > > > So I think this's a fake uninitialized warning (Maybe I'm wrong. But if I'm right, > better to specify that in commit log). Yes, you are right. Sorry, I did not analyse the code logic carefully. > > Anyway, I personally don't object to initialize a pointer to NULL at beginning, > and make a build warning disappear. Leave the decision to maintainer :) I will improve the commit. > > Thanks, > Zorro Thanks, Sun Ke > >> Signed-off-by: Sun Ke <sunke32@huawei.com> >> --- >> src/swapon.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/src/swapon.c b/src/swapon.c >> index afaed405..fe8949a3 100644 >> --- a/src/swapon.c >> +++ b/src/swapon.c >> @@ -41,7 +41,7 @@ int main(int argc, char **argv) >> .sa_handler = handle_signal, >> }; >> enum verbs verb = TEST_SWAPON; >> - void *p; >> + void *p = NULL; >> ssize_t sz; >> int fd = -1; >> int ret, c; >> -- >> 2.13.6 >> > .
diff --git a/src/swapon.c b/src/swapon.c index afaed405..fe8949a3 100644 --- a/src/swapon.c +++ b/src/swapon.c @@ -41,7 +41,7 @@ int main(int argc, char **argv) .sa_handler = handle_signal, }; enum verbs verb = TEST_SWAPON; - void *p; + void *p = NULL; ssize_t sz; int fd = -1; int ret, c;
when run make, show: swapon.c:135:3: warning: 'p' may be used uninitialized in this function [-Wmaybe-uninitialized] memcpy(p, buf, BUF_SIZE); ^~~~~~~~~~~~~~~~~~~~~~~~ fix it. Signed-off-by: Sun Ke <sunke32@huawei.com> --- src/swapon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)