How come if condition not work?

Question

           rc = daoMp.retrieveSystemData(argv[2]);
           printf("rc = %d\n");
           if (rc == 0) {
               ErrLog("Mount point found\n");
               printf("Mount point found\n");
               return 4;
           }
           else {
               ErrLog("Could not retrieve system data\n");
               printf("Could not retrieve system data\n");
               return -1;
           }

Output: rc = -208814497
Mount point found

How come, if block validation fails?

You have evoked Undefined Behavior best avoided by not using crappy, type-unsafe C-style calls in the first place. — John Dibling, Feb 05 '14 at 15:40
Sorry, i didn't understand. There are other parts of code that uses something like `if (rc < 0)` and i followed the same. What do i miss here? Can someone help me? — RajSanpui, Feb 05 '14 at 15:44
look at the answers. rc equals to zero but you don't print rc, you print garbage (-208814497) — Hayri Uğur Koltuk, Feb 05 '14 at 15:47
You're writing in C++, but this code reads like C. The answer is easy: [don't write like it were C](http://stackoverflow.com/questions/5328873/c-streams-vs-c-style-io). For a newbie the C-style is much more error prone, and I highly discourage it for people with little experience. — Kuba hasn't forgotten Monica, Feb 05 '14 at 16:36

score 5 · Accepted Answer · answered Feb 05 '14 at 15:41

5

Instead of this (which you're calling incorrectly, one argument too short):

printf("rc = %d\n");

Do this:

std::cout << "rc = " << rc << '\n';

That way, you'll use the proper C++ way of doing this (which would immediately tell you something's off). printf() is inherited from C and it's inherently unsafe - your error is a prime example of why.

answered Feb 05 '14 at 15:41

Angew is no longer proud of SO

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But C++ is a superset of C, why it won't work i wonder. Any hints please? – RajSanpui Feb 05 '14 at 16:10
@kingsmasher1 1. C++ is not a superset of C. 2. As I'm saying in the answer, you're calling `printf()` with one argument too short - you're not actually passing `rc` into the function. – Angew is no longer proud of SO Feb 05 '14 at 16:52

score 1 · Answer 2 · answered Feb 05 '14 at 15:37

1

I believe you are missing second parameter to printf:

printf("rc = %d\n", rc);

answered Feb 05 '14 at 15:37

Hayri Uğur Koltuk

2,970
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score 0 · Answer 3 · answered Feb 05 '14 at 15:37

0

printf("rc = %d\n"); should be printf("rc = %d\n", rc);

answered Feb 05 '14 at 15:37

Sunil Bojanapally

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How come if condition not work?

3 Answers3