non-void function

[Roman Mashak]

Hello, All!

Assume I wrote function like:

/* authenticate client */
int cli_auth(char *user_id, char *user_pass)
{
MYSQL conn;
if ( db_init(&conn) == 0 ) {
if ( db_search(&conn, user_id, user_pass) != AUTH_PASS ) return
AUTH_FAIL;
}
else return FAIL;
}

....
if ( cli_auth(msg_id, msg_passwd) == AUTH_FAIL ) {
...
}

Compiling it with gcc, I get the warnings:

#gcc -g -Wall -o server server.c
server.c: In function `cli_auth':
server.c:33: warning: control reaches end of non-void function

Seems like standard requires non-void function to return something, in my
case function always returns some value. Then, why do I get warning?

With best regards, Roman Mashak. E-mail: (e-mail address removed)

 

[Artie Gold]

Hello, All!

Assume I wrote function like:

/* authenticate client */
int cli_auth(char *user_id, char *user_pass)
{
MYSQL conn;
if ( db_init(&conn) == 0 ) {
if ( db_search(&conn, user_id, user_pass) != AUTH_PASS ) return
AUTH_FAIL;

What happens if the above condition is not true?
Answer: there is no return value!

....and there's where you get the warning.

}
else return FAIL;
}

...
if ( cli_auth(msg_id, msg_passwd) == AUTH_FAIL ) {
...
}

Compiling it with gcc, I get the warnings:

#gcc -g -Wall -o server server.c
server.c: In function `cli_auth':
server.c:33: warning: control reaches end of non-void function

Seems like standard requires non-void function to return something, in my
case function always returns some value. Then, why do I get warning?

Ah, but it doesn't. See above.

HTH,
--ag

 

[Peter Nilsson]

Hello, All!

Assume I wrote function like:

/* authenticate client */
int cli_auth(char *user_id, char *user_pass)
{
MYSQL conn;
if ( db_init(&conn) == 0 ) {
if ( db_search(&conn, user_id, user_pass) != AUTH_PASS )
return AUTH_FAIL;

If db_init is 0 but db_search returns AUTH_PASS, then your function
does not return a value.

}
else return FAIL;

This else condition only covers the case where db_init is non-zero.

}

...
if ( cli_auth(msg_id, msg_passwd) == AUTH_FAIL ) {
...
}

Compiling it with gcc, I get the warnings:

#gcc -g -Wall -o server server.c
server.c: In function `cli_auth':
server.c:33: warning: control reaches end of non-void function

Seems like standard requires non-void function to return something,

It doesn't require it in _all_ cases, but the behaviour is undefined if
the calling function expects a return value when one isn't supplied.

in my case function always returns some value.

Look again.

Then, why do I get warning?

The C standards has required diagnostics, but otherwise doesn't
prevent a conforming compiler from issuing warnings for whatever
else reason it feels like. You're lucky that gcc has supplied you
with such a warning in this case.

 

[Roman Mashak]

Thank you very much for replies, I got the point and fixed the code.


With best regards, Roman Mashak. E-mail: (e-mail address removed)

 

[Kenneth Brody]

Roman Mashak wrote:
[...]

int cli_auth(char *user_id, char *user_pass)
{
MYSQL conn;
if ( db_init(&conn) == 0 ) {
if ( db_search(&conn, user_id, user_pass) != AUTH_PASS ) return
AUTH_FAIL;
}
else return FAIL;
} [...]
Compiling it with gcc, I get the warnings:

#gcc -g -Wall -o server server.c
server.c: In function `cli_auth':
server.c:33: warning: control reaches end of non-void function

Seems like standard requires non-void function to return something, in my
case function always returns some value. Then, why do I get warning?

What happens if db_init() returns zero, and db_search() returns AUTH_PASS?

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>