Can you resize a C++ array after initialization? [duplicate]
C++ arrays are fixed in size. If you need a “resizable array”, you’ll want to use std::vector instead of an array.
sizeof
sizeof(struct) returns unexpected value
It’s padding the struct to fit an 8-byte boundary. So it actually is taking 40 bytes in memory – sizeof is returning the correct value. If you want it to only take 33 bytes then specify the packed attribute: struct region { public: long long int x; long long int y; long long int width; … Read more
Implementation of sizeof operator
The result of pointer subtraction is in elements and not in bytes. Thus the first expression evaluates to 1 by definition. This aside, you really ought to use parentheses in macros: #define my_sizeof(x) ((&x + 1) – &x) #define my_sizeof(x) ((char *)(&x + 1) – (char *)&x) Otherwise attempting to use my_sizeof() in an expression … Read more
sizeof single struct member in C
Although defining the buffer size with a #define is one idiomatic way to do it, another would be to use a macro like this: #define member_size(type, member) sizeof(((type *)0)->member) and use it like this: typedef struct { float calc; char text[255]; int used; } Parent; typedef struct { char flag; char text[member_size(Parent, text)]; int used; … Read more
c++ sizeof(array) return twice the array’s declared length
sizeof returns the size of a variable (in this case, your arrays), where sizeof(char) is 1. Since a char is one byte wide, sizeof returns the size of the variable in bytes. Since each short int is two bytes wide on your system, an array of 6 of them will have size 12, and an … Read more
Why do I get a warning every time I use malloc?
You need to add: #include <stdlib.h> This file includes the declaration for the built-in function malloc. If you don’t do that, the compiler thinks you want to define your own function named malloc and it warns you because: You don’t explicitly declare it and There already is a built-in function by that name which has … Read more
Why is −1 > sizeof(int)?
The following is how standard (ISO 14882) explains abort -1 > sizeof(int) Relational operator `>’ is defined in 5.9 (expr.rel/2) The usual arithmetic conversions are performed on operands of arithmetic or enumeration type. … The usual arithmetic conversions is defined in 5 (expr/9) … The pattern is called the usual arithmetic conversions, which are defined … Read more
Using sizeof() on malloc’d memory [duplicate]
Because the size of the “string” pointer is 8 bytes. Here are some examples of using sizeof() with their appropriate “size”. The term size_of() is sometimes deceiving for people not used to using it. In your case, the size of the pointer is 8 bytes.. below is a representation on a typical 32-bit system. sizeof … Read more
Using sizeof on arrays passed as parameters [duplicate]
What causes this inconsistency? The name of the array decays as an pointer to its first element. When you pass an array to an function, this decaying takes place and hence the expression passed to sizeof is a pointer thus returning pointer size. However, an array passed to sizeof always returns size of the array … Read more
What does sizeof do?
sizeof(x) returns the amount of memory (in bytes) that the variable or type x occupies. It has nothing to do with the value of the variable. For example, if you have an array of some arbitrary type T then the distance between elements of that array is exactly sizeof(T). int a[10]; assert(&(a[0]) + sizeof(int) == … Read more