ExprInspection checks¶

• void clang_analyzer_eval(bool);

  Prints TRUE if the argument is known to have a non-zero value, FALSE if the argument is known to have a zero or null value, and UNKNOWN if the argument isn’t sufficiently constrained on this path. You can use this to test other values by using expressions like “x == 5”. Note that this functionality is currently DISABLED in inlined functions, since different calls to the same inlined function could provide different information, making it difficult to write proper -verify directives.

  In C, the argument can be typed as ‘int’ or as ‘_Bool’.

  Example usage:

  clang_analyzer_eval(x); // expected-warning{{UNKNOWN}}
  if (!x) return;
  clang_analyzer_eval(x); // expected-warning{{TRUE}}
  

• void clang_analyzer_checkInlined(bool);

  If a call occurs within an inlined function, prints TRUE or FALSE according to the value of its argument. If a call occurs outside an inlined function, nothing is printed.

  The intended use of this checker is to assert that a function is inlined at least once (by passing ‘true’ and expecting a warning), or to assert that a function is never inlined (by passing ‘false’ and expecting no warning). The argument is technically unnecessary but is intended to clarify intent.

  You might wonder why we can’t print TRUE if a function is ever inlined and FALSE if it is not. The problem is that any inlined function could conceivably also be analyzed as a top-level function (in which case both TRUE and FALSE would be printed), depending on the value of the -analyzer-inlining option.

  In C, the argument can be typed as ‘int’ or as ‘_Bool’.

  Example usage:

  int inlined() {
    clang_analyzer_checkInlined(true); // expected-warning{{TRUE}}
    return 42;
  }
  
  void topLevel() {
    clang_analyzer_checkInlined(false); // no-warning (not inlined)
    int value = inlined();
    // This assertion will not be valid if the previous call was not inlined.
    clang_analyzer_eval(value == 42); // expected-warning{{TRUE}}
  }
  

• void clang_analyzer_warnIfReached();

  Generate a warning if this line of code gets reached by the analyzer.

  Example usage:

  if (true) {
    clang_analyzer_warnIfReached();  // expected-warning{{REACHABLE}}
  }
  else {
    clang_analyzer_warnIfReached();  // no-warning
  }
  

• void clang_analyzer_warnOnDeadSymbol(int);

  Subscribe for a delayed warning when the symbol that represents the value of the argument is garbage-collected by the analyzer.

  When calling ‘clang_analyzer_warnOnDeadSymbol(x)’, if value of ‘x’ is a symbol, then this symbol is marked by the ExprInspection checker. Then, during each garbage collection run, the checker sees if the marked symbol is being collected and issues the ‘SYMBOL DEAD’ warning if it does. This way you know where exactly, up to the line of code, the symbol dies.

  It is unlikely that you call this function after the symbol is already dead, because the very reference to it as the function argument prevents it from dying. However, if the argument is not a symbol but a concrete value, no warning would be issued.

  Example usage:

  do {
    int x = generate_some_integer();
    clang_analyzer_warnOnDeadSymbol(x);
  } while(0);  // expected-warning{{SYMBOL DEAD}}