malloc

来源： https://stackoverflow.com/questions/63613733/how-to-create-an-array-of-strings-of-unknown-size

问题 I'm new in programming in C and now I'm studying strings. My question is: if I allocate a string using malloc (as in the code below), is the NULL character automatically inserted at the end of the string? I find an answer in another question here, and it seems that the NULL character is not automatically included. But here comes the problem: I know functions like strlen don't work if there isn't the NULL character, and in this code I use it and it works. So I think there is \0 at the end of

问题 I was told that the following code has undefined behavior until C++20: int *p = (int*)malloc(sizeof(int)); *p = 10; Is that true? The argument was that the lifetime of the int object is not started before assigning the value to it (P0593R6). To fix the problem, placement new should be used: int *p = (int*)malloc(sizeof(int)); new (p) int; *p = 10; Do we really have to call a default constructor that is trivial to start the lifetime of the object? At the same time, the code does not have

问题 I was told that the following code has undefined behavior until C++20: int *p = (int*)malloc(sizeof(int)); *p = 10; Is that true? The argument was that the lifetime of the int object is not started before assigning the value to it (P0593R6). To fix the problem, placement new should be used: int *p = (int*)malloc(sizeof(int)); new (p) int; *p = 10; Do we really have to call a default constructor that is trivial to start the lifetime of the object? At the same time, the code does not have

问题 I want to use malloc to allocate memory, but I don't want to use a dynamic allocation way in malloc. Instead, I want to use malloc to allocate a large block/pool so that I can "new" some variables/objects into this large memory block/pool. Therefore, I would like to modify the malloc source code (e.g., malloc/malloc.c ) in glibc to make it work for my scenario. What is the most convenient and efficient way to modify glibc source codes and also test its functionality? One way that comes to my

问题 I want to use malloc to allocate memory, but I don't want to use a dynamic allocation way in malloc. Instead, I want to use malloc to allocate a large block/pool so that I can "new" some variables/objects into this large memory block/pool. Therefore, I would like to modify the malloc source code (e.g., malloc/malloc.c ) in glibc to make it work for my scenario. What is the most convenient and efficient way to modify glibc source codes and also test its functionality? One way that comes to my

问题 I want to use malloc to allocate memory, but I don't want to use a dynamic allocation way in malloc. Instead, I want to use malloc to allocate a large block/pool so that I can "new" some variables/objects into this large memory block/pool. Therefore, I would like to modify the malloc source code (e.g., malloc/malloc.c ) in glibc to make it work for my scenario. What is the most convenient and efficient way to modify glibc source codes and also test its functionality? One way that comes to my

问题 I came across an issue which I could not resolve. My question is, if I used malloc to allocate memory and then memory block is delete using delete ? The general thumb rule is If we allocate memory using malloc , it should be deleted using free . If we allocate memory using new , it should be deleted using delete . Now, in order to check what happens if we do the reverse, I wrote a small code. #include<iostream> #include<cstdio> #include<cstdlib> using namespace std; class A { int p=10; public

问题 I came across an issue which I could not resolve. My question is, if I used malloc to allocate memory and then memory block is delete using delete ? The general thumb rule is If we allocate memory using malloc , it should be deleted using free . If we allocate memory using new , it should be deleted using delete . Now, in order to check what happens if we do the reverse, I wrote a small code. #include<iostream> #include<cstdio> #include<cstdlib> using namespace std; class A { int p=10; public

问题 #include <stdio.h> int main() { char *mystring = calloc(2, sizeof(char)); scanf("%10[^\n]s", mystring); printf("\nValue: %s\nSize of array: %d\nAllocated space: %d\n", mystring, 2 * sizeof(char), sizeof(char) * strlen(mystring)); free(mystring); } Output: $ ./"dyn_mem" laaaaaaaaaaa Value: laaaaaaaaa Size of array: 2 Allocated space: 10 This code can produce an undefined behavior if I enter in the scanf input a string bigger than array size. How can I handle this ? 回答1: There are multiple