Deleting printf(""); breaks my program! I'm getting error: expected expression" making a char after switch case

Question

Is this a normal error that will happen with just a blank method? I used a custom Makefile btw.

case MODE: //mode is just an enum stackoverflow

  printf("");

  char temp = '5';

CSftp.c:335:9: error: expected expression char temp = '5';

deleting printf(""); causes the error to appear. Or is this a sympton from a problem far away.

The fact you're using a custom makefile or using make is totally irrelevant to your question. — Jabberwocky, Apr 02 '20 at 08:28

RadioSilence · Answer 1 · 2020-04-02T08:34:49.153

7

Variables should not be declared in a case without being correctly scoped by an enclosing {..} block. A good explanation can be found here. Declare char temp before the switch statement or enclose the code for the case.

Option 1:

char temp; 
switch(condition){
    ...
    case MODE:
        temp = '5';
        ...
}

Option 2:

switch(condition){
    ...
    case MODE:
    {
        char temp = '5';
        ...
    }
    case NEXT:
        ...
}

edited Apr 02 '20 at 08:34

answered Apr 02 '20 at 08:17

RadioSilence

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1
10

3

Perfectly valid to add a block-scope, e.g. `{ .... }` within a case and declare variables within. – David C. Rankin Apr 02 '20 at 08:23
3

The advice is OK but the explanation is wrong, and at any rate it doesn’t explain the problem OP is seeing. – Konrad Rudolph Apr 02 '20 at 08:23

score 7 · Answer 2 · answered Apr 02 '20 at 08:34

GCC 9.3 has a more easily understandable error message:

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

That is, C’s syntax simply forbids this because a case label needs to be attached to a syntactic statement, and declarations in C aren’t statements. But compound statements are statements, which is why surrounding the whole thing by {…} works.

score 1 · Answer 3 · answered Apr 02 '20 at 08:31

1

if you want to declare variable in the case add the block there:

switch(x)
{
    case MODE: //mode is just an enum stackoverflow
    {
        printf("");   

        char temp = '5';
    }
}

answered Apr 02 '20 at 08:31

0___________

60,014
4
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score 1 · Answer 4 · answered Apr 02 '20 at 08:34

you can only assign a value to a variable in case unless you use a block

    case MODE: 
    {
        printf("");   

        char temp = '5';
    }

but note that you only have this variable in this statement after you exit the block variable temp is no longer visible.

Deleting printf(""); breaks my program! I'm getting error: expected expression" making a char after switch case

4 Answers4