[Solved] error: ‘else’ without a previous ‘if’ with fprintf [closed]

Question

Here’s the offending code in question:

       if (xflg)
              index = m * nxy + l*nx + k;
              fprintf(stdout,"%.1f",index);
       else
          index = m * nxy + k*ny + l;

The “if” and “else” sections of this if statement originally had one line each, so adding braces wasn’t strictly necessary. But when you added the call to fprintf, that changed things.

Since the are no braces after if, the index = m * nxy + l*nx + k; line consists of the entire if part. The printf that follows is not part of the if and is a separate statement. Then when the compiler sees the else, there’s no corresponding if because the prior if is complete.

This can be fixed by adding the braces:

       if (xflg) {
              index = m * nxy + l*nx + k;
              fprintf(stdout,"%.1f",index);
       } else {
          index = m * nxy + k*ny + l;
       }

You should always add braces to any if, else, for, while, or do block, even if the body is only one line. That prevents errors like this from happening.

You were lucky in this case that failing to add braces resulted in a compiler error. If you didn’t have an else part in this example, the code would compile and the printf would always run. Then you’d be scratching your head to figure out why.

As for the printf warning, index is of type int, so you need to use the proper format specifier to print it which is %d.

Accepted Answer