What are the common pitfalls in C++ function exception handling?

C Common pitfalls in function exception handling: Avoid returning local variable references or pointers in exception handling blocks to avoid pointing to invalid memory. Do not throw exceptions repeatedly in the exception handling block to avoid overwriting the original exception information. Use the noexcept specifier with caution to ensure that the function does not throw an exception. Use smart pointers and exception specifications to improve safety and avoid dangling pointer problems.

Common traps in C function exception handling

Practical cases

Assumptions There is a function doSomething(), which may throw MyException Exception:

void doSomething() {
  if (condition) {
    throw MyException();
  }

  // 其他代码
}

Trap 1: Returning a reference in the exception handling block

Problem: If a reference to a local variable is returned in the exception handling block, when the function exits, the reference will point to invalid memory.

Code example:

string& getSomething() {
  try {
    string s = "Hello";
    return s;  // 引用局部变量 s
  } catch (exception& e) {
    // 处理异常
  }
}

Trap 2: Returning pointer in exception handling block

Problem:Similar to Trap 1, if a pointer to a local variable is returned in the exception handling block, the pointer will point to invalid memory when the function exits.

Code example:

int* getSomething() {
  int n;
  try {
    n = 10;
    return &n;  // 返回局部变量 n 的指针
  } catch (exception& e) {
    // 处理异常
  }
}

Trap 3: Throwing exceptions repeatedly

Problem:If Throw another exception again in the exception handling block, and the information of the original exception will be overwritten.

Code Example:

void doSomething() {
  try {
    throw MyException();
  } catch (MyException& e) {
    throw logic_error("New error"); // 重新抛出另一个异常
  }
}

Trap 4: Abusenoexcept

Problem: If a function is signed with the noexcept specifier but may actually throw an exception, the program may crash.

Code Example:

void myNoexceptFunction() noexcept {
  throw MyException();
}

Precautions

• Be careful when using references and pointers: Avoid returning references or pointers to local variables in exception handling blocks.
• Do not throw exceptions repeatedly: In the exception handling block, only handle the original exception to avoid throwing exceptions again.
• Use with caution noexcept: Use noexcept only if the function really does not throw any exceptions.
• Use smart pointers: Use smart pointers like std::shared_ptr to avoid dangling pointer problems.
• Use exception specifications: Specify possible exception types in the function signature to provide additional safety checks.

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