On Thu, Nov 10, 2022 at 12:43:30PM +0100, Benjamin MUGNIER wrote:
> After running smatch on my tree I couldn't reproduce this warning:
> warn: pm_runtime_get_sync() also returns 1 on success
> I'm using the latest smatch cloned from github. Do you append some
> options to kchecker to get this output ?
TL;DR: Thanks for the report! I will fix it later this week.
It's not really supposed to warn at all... The pm_runtime_get_sync()
returns negatives on error so testing for "if (ret < 0) {" is correct
as a general case. In this case it is wrong but normally it would be
the correct check.
This is an interaction with the check for uninitialized variables,
check_uninitialized.c. A common false positive was caused by mismatches
where a function checks for if (ret) but the caller checks for
if (ret < 0) {.
int function(...)
{
ret = frob();
if (ret)
^^^^^^^^
return ret;
return 0;
}
int caller(...)
{
ret = function();
if (ret < 0) {
^^^^^^^^^^^^
How should positives be treated? So what the check_uninitialized.c
check does is that it says, "let's assume that "ret >= 0" and "!ret"
are equivalent". It creates a fake environment to test what !ret means
for uninitialized variables. The check_pm_runtime_get_sync.c check sees
the "!ret" condition and says, "Nope. That's supposed to be "ret < 0"".
Smatch shouldn't be printing warnings from inside the fake environment.
regards,
dan carpenter
