A Label Can Only Be Part of a Statement and a Declaration Is Not a Statement

1. a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error in C
2. a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error When Using switch Statements in C
3. Ways to Avoid the a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error in C
4. Conclusion

While programming in any programming language, we encounter errors that result in the abnormal working of our program or halt our program until the error is resolved. This article will discuss an error known as a label can only be part of a statement and a declaration is not a statement that occurs only in the C language.

a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error in C

Errors are just some unexpected situations or illegal actions made by the programmer that results in the program’s abnormal working. These errors are of various types based on their effects.

However, some errors are not common in all programming languages but occur only in a particular language. One such error is a label can only be part of a statement and a declaration is not a statement that occurs only in the C language.

This error occurs when a declaration immediately follows a label. However, the C language standards only allow statements to follow a label, not a declaration.

A label in C language is a sequence of characters that refer to a particular location in the source code. A label is used with the goto statement in a program.

It would be used something like the below code:

#include <stdio.h>

int main() {
  goto TARGET;

TARGET:
  printf("Hello World");
  return 0;
}

Output:

Hello World

Whenever the goto statement is reached, the program control jumps to the specified label in the program. As you can see in the above program, the output is successfully printed because the label TARGET has been followed by a printf statement.

However, if we try to declare a variable after the label, the same code would give us an error because the C language standards do not allow a declaration immediately after a label. Therefore, the program would throw the a label can only be part of a statement and a declaration is not a statement error.

Let us see an example that throws such an error:

#include <stdio.h>

int main() {
  goto TARGET;

TARGET:
  char* s = "Hello World";
  printf("%s", s);
  return 0;
}

Output:

.ex1.c: In function 'main':
.ex1.c:7:5: error: a label can only be part of a statement and a declaration is not a statement
     char * s = "Hello World";
     ^

As shown in the output, the error a label can only be part of a statement and a declaration is not a statement is mentioned. Moreover, the specified problem line has also been shown, which is the declaration statement after the label TARGET.

However, had the declaration not immediately followed the label, the program would have worked fine. Let us see an example of that as well.

#include <stdio.h>

int main() {
  goto TARGET;

TARGET:
  printf("%d", 2 + 5);
  char* s = "Hello World";
  printf("%s", s);
  return 0;
}

Output:

7Hello World

Therefore, the error a label can only be part of a statement and a declaration is not a statement only occurs when a declaration immediately follows a label in a program. No error was thrown when we added a printf statement after the label and the declaration.

a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error When Using switch Statements in C

The error that a label can only be part of a statement and a declaration is not a statement also occurs while using the switch statement in C. This is because the C language treats the cases similar to labels.

Therefore, whenever we try to declare anything just after a case, the error a label can only be part of a statement and a declaration is not a statement is thrown to the user.

Let us see an example of the same:

#include <stdio.h>

int main() {
  char ch = 'A';
  switch (ch) {
    case 'A':
      char* s = "Case A";
      printf("%s", s);
      break;
  }
}

Output:

.ex1.c: In function 'main':
.ex1.c:8:7: error: a label can only be part of a statement and a declaration is not a statement
       char * s = "Case A";
       ^

Therefore, as you can see in the above output, the same error has been thrown when using the switch statements in C when we try declaring the variable s immediately after case A.

Ways to Avoid the a Label Can Only Be Part of a Statement and a Declaration Is Not a Statement Error in C

Now, we will discuss how this error a label can only be part of a statement and a declaration is not a statement can be resolved.

We can avoid this error by simply putting a semi-colon after the label. The compiler will treat the semi-colon as a blank statement and will not throw an error.

Let us see the above solution with the help of an example.

#include <stdio.h>

int main() {
  goto TARGET;

TARGET:;
  char* s = "Hello World";
  printf("%s", s);
  return 0;
}

Output:

Hello World

Now, you can see in the above code that by adding a semi-colon after the label TARGET, we can declare the variable s immediately after the label. It would not throw the error a label can only be part of a statement and a declaration is not a statement.

As discussed earlier, the same error also occurs while dealing with the switch statements because the cases are considered similar to labels in the C language.

Therefore, to resolve the error in the switch statements, we can either add a semi-colon after a case or put curly braces around the block of a case in a switch statement. Either of the ways would resolve our error.

Let us look at the code with a semi-colon after a case:

#include <stdio.h>

int main() {
  char ch = 'A';
  switch (ch) {
    case 'A':;
      char* s = "Case A";
      printf("%s", s);
      break;
  }
}

​Output:

Case A

Therefore, as you can see, just by adding a semi-colon, the error a label can only be part of a statement and a declaration is not a statement is resolved.

Now, let us resolve the error by adding a pair of curly braces around the block of the label.

#include <stdio.h>

int main() {
  char ch = 'A';
  switch (ch) {
    case 'A': {
      char* s = "Case A";
      printf("%s", s);
      break;
    }
  }
}

Output:

Case A

We have resolved the error by adding a pair of curly braces around the statements of the case A.

Conclusion

In this article, we have discussed the error a label can only be part of a statement and a declaration is not a statement in detail. The C language standards only allow statements after a label and do not permit declarations immediately after a label which causes the error to be thrown.

To resolve the error, we could use a semi-colon after the label and a pair of curly braces around the block of the label in the case of switch statements in C.