# Extra Clang Tools 21.1.8 documentation

## clang-tidy - bugprone-suspicious-missing-comma

# bugprone-suspicious-missing-comma

String literals placed side-by-side are concatenated at translation phase 6 (after the preprocessor). This feature is used to represent long string literal on multiple lines.

For instance, the following declarations are equivalent:

    const char* A[] = "This is a test";
    const char* B[] = "This" " is a "    "test";

A common mistake done by programmers is to forget a comma between two string literals in an array initializer list.

    const char* Test[] = {
      "line 1",
      "line 2"     // Missing comma!
      "line 3",
      "line 4",
      "line 5"
    };

The array contains the string “line 2line3” at offset 1 (i.e. Test[1]). Clang won’t generate warnings at compile time.

This check may warn incorrectly on cases like:

    const char* SupportedFormat[] = {
      "Error %s",
      "Code " PRIu64,   // May warn here.
      "Warning %s",
    };

## Options

SizeThreshold

  An unsigned integer specifying the minimum size of a string literal to be considered by the check. Default is `5U`.

RatioThreshold

  A string specifying the maximum threshold ratio [0, 1.0] of suspicious string literals to be considered. Default is `".2"`.

MaxConcatenatedTokens

  An unsigned integer specifying the maximum number of concatenated tokens. Default is `5U`.