Display return value from a function

mapleleafblue · 06-30-2009, 05:04 AM

I want to print a return value of 1 or 0 or some other number in a c program to the screen.

Code:

  if ( readFile() != 0 )
        {
   
                fprintf(stderr, "Unable to read input file!\n");
                program_exit(E_FILES_READ);
        }
      printf("equals zero \n");

int readFile()
{
        char revAccName[51];
        char custSortCode[7];
        char custAccNum[9];
        char custAccName[19];
        char amount[12];
        char date[9];
        char id1[21];
        char id2[21];
        char id3[21];
        char reason[2];
        char record[292];
        cur = &head;
        for(;;)
        {
                if ( !fgets(record, 291, inFile) )
                        break;
                if (strlen(record) < 101)
                        return 1;
                strncpy(revAccName, &record[5], 50);
                revAccName[50] = 0;
                strncpy(custSortCode, &record[55], 6);
                custSortCode[6] = 0;
                strncpy(custAccNum, &record[61], 8);
                custAccNum[8] = 0;
                strncpy(custAccName, &record[69], 18);
                custAccName[18] = 0;
                strncpy(amount, &record[87], 11);
                amount[11] = 0;
                strncpy(id1, &record[106], 20);
                id1[20] = 0;
                strncpy(id2, &record[126], 20);
                id2[20] = 0;
                strncpy(id3, &record[146], 20);
                id3[20] = 0;
                strncpy(reason, &record[166], 1);
                reason[1] = 0;

                /* Allocate space for the record and hook it up to list. */
                *cur = (unpaids_t *)calloc(1, sizeof(unpaids_t));
                if (!*cur)
                        return 1;
                strcpy((*cur)->revAccName, &revAccName[strspn(revAccName," ")]);
                strcpy((*cur)->custSortCode, &custSortCode[strspn(custSortCode," ")]);
                strcpy((*cur)->custAccNum, &custAccNum[strspn(custAccNum," ")]);
                strcpy((*cur)->custAccName, &custAccName[strspn(custAccName," ")]);
                strcpy((*cur)->amount, &amount[strspn(amount," ")]);
                strcpy((*cur)->id1, &id1[strspn(id1," ")]);
                strcpy((*cur)->id2, &id2[strspn(id2," ")]);
                strcpy((*cur)->id3, &id3[strspn(id3," ")]);
                strcpy((*cur)->reason, &reason[strspn(reason," ")]);
                (*cur)->next = NULL;
                cur = &((*cur)->next);
        }
}

The program originally worked like this.

Since moving to a new unix box it fails. Do we think the version of the OS needs to explicitly have a return 0;

It's not my code it's someone elses and I am loathe to change anything because it has always worked before.

Sun 5.9 original

SunOS 5.10 now.

Adding in the return 0 fixes it. But the program does work on 5.9

I would also maybe like to print the return code any suggestions ?

MK27 · 06-30-2009, 05:52 AM

Quote:

Originally Posted by mapleleafblue

I want to print a return value of 1 or 0 or some other number in a c program to the screen.

Since moving to a new unix box it fails. Do we think the version of the OS needs to explicitly have a return 0;

It's not my code it's someone elses and I am loathe to change anything because it has always worked before.

Adding in the return 0 fixes it. But the program does work on 5.9

Of course you should add a return value. If the type of the function is int, it must return a value, even if that value is always the same (0).

The fact that it worked somewhere once does not mean it is or ever was correct. It is not proper C code without the return value, so don't feel bad about correcting it no matter who wrote it. The reason it probably worked before is because 0 == untrue in C, so perhaps the other compiler automatically assigned untrue to a function that had no proper return value; in other words, that programmer was relying on *luck* because this is "undefined behavior" (and this programmer obviously did not test it on more than one compiler and possibly ignored warnings on the one that does make it work).

Zlatko · 06-30-2009, 05:53 AM

you need a return statement at the bottom of your function. It may seem to work on some systems because you are unlucky, but the return value will be undefined if there is not explicit return statement.

itCbitC · 06-30-2009, 11:27 AM

Quote:

Originally Posted by mapleleafblue

Since moving to a new unix box it fails. Do we think the version of the OS needs to explicitly have a return 0;

It's not my code it's someone elses and I am loathe to change anything because it has always worked before.

Sun 5.9 original

SunOS 5.10 now.

Adding in the return 0 fixes it. But the program does work on 5.9

I would also maybe like to print the return code any suggestions ?

It's not the OS but the compiler version that needs to be looked at. If a function doesn't have an explicit return, the compiler will put one in for you. A free return statement is supplied at the end of each function definition, so running off the end causes control, but no value, to be returned to the caller. The OS has nothing to do with it so your best bet is to insert a return statement and not leave anything to chance or the compiler

.

Here's something you can try. Compile the source on 5.9 and move the executable to the 5.10 box and run it there to see if that makes a difference. If backwards compatibility is preserved in the compiler versions, this should work and pinpoint the cause.

slingerland3g · 06-30-2009, 12:06 PM

You do in fact have return values for your function:

Code:

...

if (strlen(record) < 101)
                        return 1;
...

if (!*cur)
                        return 1;

The problem here is that either one of those will have to be successful in order to satisfy the return value of the function call. From the use of your for(;

you better!

06-30-2009, 05:53 AM	#3
Zlatko pwning noobs Join Date: Jun 2009 Location: The Great White North Posts: 125	you need a return statement at the bottom of your function. It may seem to work on some systems because you are unlucky, but the return value will be undefined if there is not explicit return statement. __________________ Sun Certified Java Programmer / Developer IEEE CSDP
Zlatko is offline

06-30-2009, 12:06 PM	#5
slingerland3g Registered User Join Date: Jan 2008 Location: Seattle Posts: 476	You do in fact have return values for your function: Code: ... if (strlen(record) < 101) return 1; ... if (!*cur) return 1; The problem here is that either one of those will have to be successful in order to satisfy the return value of the function call. From the use of your for(; you better!
slingerland3g is offline

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