1. Freeing a null pointer wont result in any error; The free() call would return without doing anything.
2. p=calloc(
1,
sizeof(
int));
free(p);
p=realloc(p,
sizeof(
int));
Error: "glibc detected ** ... : double free or corruption" Reason: "realloc(ptr,size)" has to be invoked after (m|c)alloc(), but before free()
3. p=calloc(
1,
sizeof(
int));
free(p);
p=
NULL;
p=realloc(p,
sizeof(
int));
No error
"realloc(,size)" is equivalent to "malloc(size)"
4.
int *p;
p=calloc(
1,
sizeof(
int));
free(p);
p=realloc(p,
0 *
sizeof(
int));
p=
NULL;
p=realloc(p,
1 *
sizeof(
int));
*p=
1;
free(p);
Error: "glibc detected ** ... : double free or corruption"
Reason: realloc(,0) is equivalent to free(); So we end up with double free
5.
int *mp,*cp;
mp=(
int*)malloc(
sizeof(
int));
printf("mp=%d\n",*mp);
cp=(int*)calloc(sizeof(int),1);
printf("cp=%d\n",*cp);
mp=garbage value
cp=0The memory space allocated by malloc is uninitialized, so mp has some garbage value. calloc initilize the allocated memory space to zero. so cp=0
6.#include
void main()
{
char *pd,*ps="I LOVE C";
pd=malloc(strlen(ps));
strcpy(pd,ps);
printf("%s",pd);
free(pd);
}
prints I LOVE C
7. int *p;
p=(int *)malloc(-10);
printf("p=%d",*p);
free(p);
Segmentation Fault
8. int *p;
p=(char *)malloc(sizeof(10));
printf("The starting address is %d\n",p);
return 0;
Will give a warning,but run anyway
ptr = (cast *)malloc(size) Malloc returns void * which is explicitly casted to cast *.
printf("%d\n", sizeof(++x));
x is not incremented since sizeof doesn't evaluate its operand.
long long a;
int b;
int c;
a = b + c;
then expecting that no matter how big b and c are that they won't overflow because a is big enough. But in reality the calculation is done by adding c in to b, which might overflow b. The value of b is then assigned to a.
Using a = (long long) b + c; yielded the correct result.
#define myCharPointer char*
int main(){
myCharPointer p1, p2;
...
}
That's one of the reasons you should use typedef instead of #define
//courtesy: stackexchange for programmers
