Re: [PATCH] conf, tap: Silence two false positive invalidFunctionArg from cppcheck

[Laine Stump <laine@redhat.com>]

On 2/16/23 5:53 PM, David Gibson wrote:
> On Thu, Feb 16, 2023 at 07:22:10PM +0100, Stefano Brivio wrote:
>> The newly introduced die() calls exit(), but cppcheck doesn't see it
>> and warns about possibly invalid arguments used after the check which
>> triggers die(). Add return statements to silence the warnings.
>>
>> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> 
> Oof, that's super ugly.  Any chance that cppcheck will recognize the
> ((noreturn)) attribute if we added it to die()?

Why is this only a problem in these two files?

(and is there a "make check" target that I should have been running and 
haven't?)

Requiring an extra "return" after die() kind of removes the advantage of 
using it over err(). :-/ If we have to do that, it would be more 
straightforward to just use err() followed by exit() directly.

> 
>> ---
>>   conf.c | 3 +++
>>   tap.c  | 6 +++++-
>>   2 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/conf.c b/conf.c
>> index 675d961..5426c9b 100644
>> --- a/conf.c
>> +++ b/conf.c
>> @@ -1036,6 +1036,9 @@ static void conf_ugid(char *runas, uid_t *uid, gid_t *gid)
>>   	if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0) {
>>   		die("Can't determine if we're in init namespace: %s",
>>   		    strerror(errno));
>> +
>> +		/* Silence cppcheck's invalidFunctionArg for 'fd' in read() */
>> +		return;
>>   	}
>>   
>>   	if (read(fd, buf, BUFSIZ) != sizeof(root_uid_map) ||
>> diff --git a/tap.c b/tap.c
>> index 88eed88..d6f962e 100644
>> --- a/tap.c
>> +++ b/tap.c
>> @@ -1037,9 +1037,13 @@ static void tap_sock_unix_init(struct ctx *c)
>>   			snprintf(path, UNIX_PATH_MAX - 1, UNIX_SOCK_PATH, i);
>>   
>>   		ex = socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0);
>> -		if (ex < 0)
>> +		if (ex < 0) {
>>   			die("UNIX domain socket check: %s", strerror(errno));
>>   
>> +			/* Silence cppcheck's invalidFunctionArg for 'ex' */
>> +			return;
>> +		}
>> +
>>   		ret = connect(ex, (const struct sockaddr *)&addr, sizeof(addr));
>>   		if (!ret || (errno != ENOENT && errno != ECONNREFUSED &&
>>   			     errno != EACCES)) {
>