As a preface, this program will not necessarily run exactly like how it does in the question as it exhibits implementation-defined behavior. In addition to this, tweaking the program slightly can cause undefined behavior as well. More information on this at the end. The first line of the main function defines an unsigned long foo … Read more
The problem is not related to references itself. The problem is that in C++, object lifetime is managed differently than in Java or other run-time environments that use a garbage collector. C++ doesn’t have standard built-in garbage collector. C++ object lifetime can be automatic (within local or global scope) or manual (explicitly allocated/deallocated in heap). … Read more
If you have a FILE* other than stdin, you can use: rewind(fptr); or fseek(fptr, 0, SEEK_SET); to reset the pointer to the start of the file. You cannot do that for stdin. If you need to be able to reset the pointer, pass the file as an argument to the program and use fopen to … Read more
You can do it like so: static struct PipeShm * myPipe = &(struct PipeShm) { .init = 0, /* … */ }; This feature is called a “compound literal” and it should work for you since you’re already using C99 designated initializers. Regarding the storage of compound literals: 6.5.2.5-5 If the compound literal occurs outside … Read more
Why should anyone compare function pointers? Here’s one example: #include <stdbool.h> /* * Register a function to be executed on event. A function may only be registered once. * Input: * arg – function pointer * Returns: * true on successful registration, false if the function is already registered. */ bool register_function_for_event(void (*arg)(void)); /* * … Read more
TL/DR: the book is wrong. What am I missing? Nothing, as far as I can see. Even the erratum version presented in comments … A pointer to void will never be equal to another pointer to void. … simply is not supported by the C language specification. To the extent that the author is relying … Read more
There is a difference in the * usage when you are defining a variable and when you are using it. In declaration, int *myVariable; Means a pointer to an integer data type. In usage however, *myVariable = 3; Means dereference the pointer and make the structure it is pointing at equal to three, rather then … Read more
A handle is usually an opaque reference to an object. The type of the handle is unrelated to the element referenced. Consider for example a file descriptor returned by open() system call. The type is int but it represents an entry in the open files table. The actual data stored in the table is unrelated … Read more
First, Go technically has only pass-by-value. When passing a pointer to an object, you’re passing a pointer by value, not passing an object by reference. The difference is subtle but occasionally relevant. For example, you can overwrite the pointer value which has no impact on the caller, as opposed to dereferencing it and overwriting the … Read more
It’s a bit more complicated. In C++03 and C++11, &var is a constant expression if var is a local static / class static or namespace scope variable. This is called an address constant expression. Initializing a class static or namespace scope pointer variable with that constant expression is guaranteed to be done before any code … Read more