switch‐case - chunhualiao/public-docs GitHub Wiki

no inner indentation

Yes, that version of the code will work just fine — even though all the statements are at the same indentation level — because:

✅ No variable declarations inside case labels

In your example:

switch(ch){
  case '\n':
  foundNewLine = true;
  break;
  case '\t':
  foundHorizontalTab = true;
  break;
}

You're only executing statements, not declaring new variables. The compiler has no issue with this because:

• Control flow (switch and case) does not violate any rules when simply executing statements like assignments or function calls.
• There are no jumps into the middle of variable initializations, which is what causes errors when variables are declared.

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🔍 Indentation vs. Syntax

• Indentation is purely for human readability.
• The compiler doesn’t care if everything is left-aligned, indented nicely, or in a single line — it only parses tokens and braces, not whitespace (outside of preprocessing).

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✅ So this works because:

• You're not declaring any variables inside the case blocks.
• You're using simple, executable statements, which are allowed without additional scope {}.

---

If you later need to declare a variable inside one of those case blocks, then yes — you'll need to wrap that case block in braces {} as shown in the previous answer.

jum to case label

The error you're seeing:

translator_processed_files/rose_fileFilter.C:95:14: error: jump to case label
   95 |         case '\t':
      |              ^~~~

is caused by declaring variables inside a switch case without proper scoping. C++ does not allow variable declarations directly inside case labels without a compound statement ({} block) to scope them. This is because control flow can "jump" into the middle of a declaration, which would violate the language's rules.

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Problem Code:

switch(ch){
  case '\n':
    int testVar19 = 42;   // <-- error-prone
    foundNewLine = true;
    int anotherTestVar19 = 24;
    int testVar20 = 42;
    break;
  case '\t':
    int testVar21 = 42;   // <-- also problematic
    foundHorizontalTab = true;
    int anotherTestVar21 = 24;
    int testVar22 = 42;
    break;
}

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✅ Corrected Version:

Wrap the code under each case in its own block {} to define a local scope:

switch(ch){
  case '\n': {
    int testVar19 = 42;
    foundNewLine = true;
    int anotherTestVar19 = 24;
    int testVar20 = 42;
    break;
  }
  case '\t': {
    int testVar21 = 42;
    foundHorizontalTab = true;
    int anotherTestVar21 = 24;
    int testVar22 = 42;
    break;
  }
}

---

Why This Happens:

The C++ standard prohibits jumping past the initialization of a variable with non-trivial constructor/destructor (which applies even to trivial types like int for safety reasons). Declaring variables directly in a case label without a block would allow control to "jump" over their initialization.

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Fix Summary:

Wrap each case body in curly braces { ... } if you're declaring variables inside it.