Const modifier participates in real parameters

It is best to regard const as a part of the parameter, and keep the form parameters consistent with the real parameters. The following example shows when an error occurs when the real parameters involved in the form participate in the const modification is inconsistent, when and why.

# Include <iostream> using namespace STD; void string_copy (char *) {cout <"string_copy invoked";} int main () {const char * pc_str = "this is a test"; string_copy (pc_str );}

Note the aboveCode, The form parameter is char *, and the real parameter is of the const char * type. This method is not compiled. The parameter is char *, so the content to which it points can be changed inside the function. However, the real parameter we pass to it is const char *, meaning that the content to which the real parameter points does not want to be changed, the compiler detects this conflict and reports an error. Next, let's exchange the writing method. The real parameter is changed to char * and the form parameter is changed to const char *. Is there a problem?

# Include <iostream> using namespace STD; void string_copy (const char *) {cout <"string_copy invoked";} int main () {char * pc_str = "this is a test"; string_copy (pc_str );}

Practice has proved that it can be compiled and passed, because the content pointed to by the parameter cannot be changed. Both the const char * and char * parameters can meet the conditions, so no error is reported, however, a warning is reported, which is not recommended by the compiler. This is not easy to understand. Conclusion: real parameters cannot have more restrictions than the actual parameters.