Mặc dù bạn có thể thấy rằng chức năng thực sự là f (int), trình biên dịch không biết điều này bởi vì nó đã nói - thông qua một tuyên bố rõ ràng rằng chức năng f (char). Như vậy, biên dịch thành công. Trong C, các mối liên kết cũng sẽ được thành công, nhưng không phải trong C + + | Improved error checking The have been used up to this point without defining them although assert has also been used to help detect programmer errors where it s appropriate . Now it s time to define this header file. Inline functions are convenient here because they allow everything to be placed in a header file which simplifies the process of using the package. You just include the header file and you don t need to worry about linking an implementation file. You should note that exceptions presented in detail in Volume 2 of this book provide a much more effective way of handling many kinds of errors - especially those that you d like to recover from -instead of just halting the program. The conditions that handles however are ones which prevent the continuation of the program such as if the user doesn t provide enough command-line arguments or if a file cannot be opened. Thus it s acceptable that they call the Standard C Library function exit The following header file is placed in the book s root directory so it s easily accessed from all chapters. Test for error conditions in programs Local using namespace std for old compilers ifndef REQUIRE_H define REQUIRE_H include cstdio include cstdlib include fstream include string inline void require bool requirement const std string msg Requirement failed using namespace std if requirement fputs stderr fputs n stderr exit 1 420 Thinking in C www. BruceEckel .com inline void requireArgs int argc int args const std string msg Must use d arguments using namespace std if argc args 1 fprintf stderr args fputs n stderr exit 1 inline void requireMinArgs int argc int minArgs const std string msg Must use at least d arguments using namespace std if argc minArgs 1 fprintf stderr minArgs fputs n stderr exit 1 inline void assure std ifstream in const std string filename using namespace std if in fprintf stderr Could not open file s n exit 1 inline .
