Odd behaviour when using Clang to build a C++ static lib

Question

I am currently using Clang on the latests OSX to build a static library in C++11 and came across something that seems odd to me.

I have class C that inherits from A and B. A is used as a public interface for the users of the class and B is used as an abstract implementation, holding methods that are common to all instances of A. I come from the Java world so I'm treating A as an interface and B as an abstract class.

In class C I have a method that is inherited from B that calls two private methods defined in C. And herein lies the weirdness. If I implement the inherited method like this:

bool EPubParser::isCorrectFileType() {
  bool has_correct_file_type = false;
  bool is_compressed_file = this->isCompressedFile();
  if (this->hasRightExtension() && is_compressed_file) {
    has_correct_file_type = true;
  }

  if (has_correct_file_type) {
    LOG(DEBUG)<< "Has correct file type. " << endl;
  } else {
    LOG(DEBUG)<< "Does not have correct file type. " << endl;
  }
  return has_correct_file_type;
}

everything works fine. I can see log statements in this->isCompressedFile() being called. If I remove the temporary variable is_compressed_file and call this->isCompressedFile() directly in the condition, they don't get called. It's as if the method doesn't exist.

Am I missing something about C++? Is this a Clang bug? Is my Java background tripping me up?

Angew is no longer proud of SO · Accepted Answer · 2013-12-05 10:34:01Z

5

If you call isCompressedFile() directly as the second operand of the && operator, it will only be executed if the first operand is true - C++ boolean operators are short-circuiting (but I believe the same applies to Java).

answered Dec 5, 2013 at 10:34

Angew is no longer proud of SO

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2 Comments

ruipacheco Over a year ago

The first operand is true. I've checked.

ruipacheco Over a year ago

I'll take that back. I did have a bug in the first operand. Thanks!

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