Home/ Questions/The complete guide to a label can only be part of a statement and a declaration is not a statement
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Adam Serre
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Asked: 2022-05-11T19:13:55+00:00 In:

The complete guide to a label can only be part of a statement and a declaration is not a statement

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I don’t know what I’m doing wrong, but I’ve already lost a couple of days struggling with this. Here is my command line:

#include<stdio.h>

int main() {
  char option = 'a';
  switch (option)
  {
    case 'a':
      char * str = "Case 'a' hit.";
      printf("%s", str);
      break;
  }

}

This returns:

a label can only be part of a statement and a declaration is not a statement

I don’t have any experience with a label can only be part of a statement and a declaration is not a statement. In this case, how should I change?

gcc
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2 Answers

  1. Best Answer
    Expert

    The cause: The error occurs when using switch statement in C, because ​the language treats cases similar to labels.

    Solution: After the case ‘a’ statement on line 7 needs to add a semi-colon. Alternatively, the entire case can be enclosed in curly braces to circumvent the error.

    #include<stdio.h>

int main() {
  char option = 'a';
  switch (option)
  {
    case 'a': ;
      char * str = "Case 'a' hit.";
      printf("%s", str);
      break;
  }
}

     

    • 14

  2. This is a peculiarity of C grammar. This is a quirk of the C grammar. A label cannot appear immediately prior to a declaration, such as char *str ...;. It can only appear before a assertion (printf(...);). This was not a problem in C89 because declarations could only be placed at the beginning of a block. You could move the label down to avoid this issue. C99 allows you to mix code and declarations, but you cannot place a label directly before a declaration.

    To make the label empty, you can place a semicolon after Renan’s colon. This is what I would do with machine-generated code. You can also raise the declaration up to the top of your function. 

    int main (void) 
{
 char *str;
 printf("Hello ");
 goto Cleanup;
Cleanup:
 str = "World\n";
 printf("%s\n", str);
 return 0;
}
    • 9

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