Memory Allocation Questions

C memory lifetime — what is printed when returning a pointer to a local array? /* program */ #include<stdio.h> #include<string.h> int main() { char *s; char *fun(); s = fun(); printf("%s ", s); return 0; } char fun() { char buffer[30]; strcpy(buffer, "RAM"); return buffer; / returning address of a local array */ } Predict the output.

C dynamic allocation — how many bytes are reserved by this call? #include<stdio.h> #include<stdlib.h> int main() { int p; p = (int ) malloc(256 * 256); if (p == NULL) printf("Allocation failed"); return 0; } Assume the request succeeds. How many bytes does malloc attempt to reserve?

C unions — what is printed after storing a float in a union and reading it back? #include<stdio.h> #include<stdlib.h> int main() { union test { int i; float f; char c; }; union test *t = (union test *) malloc(sizeof(union test)); t->f = 10.10f; printf("%f", t->f); return 0; } Assume malloc succeeds.

C on a 16-bit platform — what does sizeof(p) print for an int* allocated with malloc? #include<stdio.h> #include<stdlib.h> int main() { int p = (int ) malloc(20); printf("%d ", (int) sizeof(p)); free(p); return 0; } Assume a classic 16-bit memory model.

C after free — what does printing the pointer value show? #include<stdio.h> #include<stdlib.h> int main() { int *p; p = (int ) malloc(20); / Assume, for illustration, p held address 1314 / free(p); printf("%u", p); / Printing pointer with %u is itself non-portable / return 0; } What will be the output conceptually?

C pointers to arrays — sizes when int is 2 bytes. #include<stdio.h> #include<stdlib.h> #define MAXROW 3 #define MAXCOL 4 int main() { int (p)[MAXCOL]; p = (int ()[MAXCOL]) malloc(MAXROW * sizeof(*p)); printf("%d, %d ", (int) sizeof(p), (int) sizeof(*p)); return 0; } Assume sizeof(int) = 2. What is printed?

C pointer-to-array allocation — total bytes allocated when int is 2 bytes. #include<stdio.h> #include<stdlib.h> #define MAXROW 3 #define MAXCOL 4 int main() { int (p)[MAXCOL]; p = (int ()[MAXCOL]) malloc(MAXROW * sizeof(*p)); return 0; } Assume sizeof(int) = 2. How many bytes does malloc request?