sizeof

问题 I understand that the end of a string is indicated by a null character, but i cannot understand the output of the following code. #include <stdio.h> #include <string.h> int main(void) { char s[] = "Hello\0Hi"; printf("%d %d", strlen(s), sizeof(s)); } OUTPUT: 5 9 If strlen() detects the end of the string at the end of o, then why doesn't sizeof() do the same thing? Even if it doesn't do the same thing, isn't '\0' A null character (i.e, only one character), so shouldn't the answer be 8? 回答1:

问题 The sizeof() operator in C gives the size of its operand at compile time. It does not evaluate its operand. For example, int ar1[10]; sizeof(ar1) // output 40=10*4 sizeof(ar1[-1]) // output 4 int ar2[ sizeof(ar1) ]; // generate an array of 40 ints. When it came to C++ template class, I find some strange result. template<typename T> struct S{ T a; }; sizeof( S<int> ) // output 4 sizeof( S<bool> ) // output 1 sizeof( vector<int> ) // output 24 sizeof( vector<char> ) // output 24 sizeof( vector

问题 This question already has answers here : Are a, &a, *a, a[0], &a[0] and &a[0][0] identical pointers? (8 answers) Closed 6 years ago . I got the output for the following code as -> 6 I was confused by the output, so I changed a small portion of code and checked it. I substituted this int * ptr=(int*)(a+1) for the Not clear statement, I got the output as --> 1 . How? I heard &a , a , a[0] all are same address? what makes it different? #include<stdio.h> int main() { int a[] = {1, 2, 3, 4, 5, 6};

问题 Following the Microsoft Azure documentation for Python developers. The azure.storage.blob.models.Blob class does have a private method called __sizeof__() . But it returns a constant value of 16, whether the blob is empty (0 byte) or 1 GB. Is there any method/attribute of a blob object with which I can dynamically check the size of the object? To be clearer, this is how my source code looks like. for i in blobService.list_blobs(container_name=container, prefix=path): if i.name.endswith('.json

问题 Following the Microsoft Azure documentation for Python developers. The azure.storage.blob.models.Blob class does have a private method called __sizeof__() . But it returns a constant value of 16, whether the blob is empty (0 byte) or 1 GB. Is there any method/attribute of a blob object with which I can dynamically check the size of the object? To be clearer, this is how my source code looks like. for i in blobService.list_blobs(container_name=container, prefix=path): if i.name.endswith('.json

问题 Is this well defined behaviour or is it undefined / somehow else defined which foo (data type or identifier) sizeof will be operating on ? typedef int foo; int main(int argc, char *argv[]) { char foo; printf ("%u\r\n", sizeof(foo)); return 0; } If it is well defined, is there a way I could obtain the size of the datatype foo without declaring a variable of that type only to use sizeof on it? 回答1: C does not have explicit scope resolution, so identifiers (variable names, typedef names, struct

问题 Even with int foo(char str[]); which will take in an array initialized to a string literal sizeof doesn't work. I was asked to do something like strlen and the approach I want to take is to use sizeof on the whole string then subtract accordingly depending on a certain uncommon token. Cuts some operations than simply counting through everything. So yea, I tried using the dereferencing operator on the array(and pointer too, tried it) but I end up getting only the first array element. How can I

问题 I was getting realloc(): invalid next size for a program. So I just coded this to understand what's happening. #include <stdio.h> #include <stdlib.h> int main() { char *inp; printf("%lu ",sizeof(inp)); char *res = (char*)malloc(15*sizeof(char*)); printf("%lu ",sizeof(res)); res = "hello world"; printf("%lu\n",sizeof(res)); return 0; } And surprisingly it outputs 8 8 8 . Can anyone explain why is it like that? Why is it 8 by default? And how malloc() effects size of inp ? 回答1: You are using

问题 I am using code below and getting different values. int *p; printf("Size of *p = %d", sizeof(*p)); // Here value is 4 printf("Size of p = %d", sizeof(p)); // Here value is 8 Can any one please explain, what exactly is the reason behind this? 回答1: For any pointer variable p , the variable p itself is the pointer and the size of it is the size of the pointer. *p is what p is pointing to, and the size of *p is the size of what is being pointed to. So when sizeof(p) reports 8 then you know that a

问题 I am using code below and getting different values. int *p; printf("Size of *p = %d", sizeof(*p)); // Here value is 4 printf("Size of p = %d", sizeof(p)); // Here value is 8 Can any one please explain, what exactly is the reason behind this? 回答1: For any pointer variable p , the variable p itself is the pointer and the size of it is the size of the pointer. *p is what p is pointing to, and the size of *p is the size of what is being pointed to. So when sizeof(p) reports 8 then you know that a