What is the output (to stdout) of this C code, assuming all these lines will execute on the CPU uninterrupted? (assume p has address 1314)

Question

BlackTom AI · Accepted Answer

Freeing memory does not change the pointer value, so p still contains the same numeric address after free(p).

Relevant concepts:
- malloc returns a pointer (here cast to int*), so after p = (int*)malloc(20) the variable p holds the address (given as 1314).
- free(p) releases the allocated block but does not modify the pointer variable; it still stores 1314 unless you explicitly assign p = NULL.
- printf("%u", p) prints an unsigned integer. Treating a pointer with %u is technically undefined by the C standard if sizeof(unsigned) != sizeof(void*), but the question gives the address and assumes the call will print that numeric value.

Step-by-step reasoning:
1. p is declared: int *p;
2. p = (int *)malloc(20); // p now equals the address 1314 (by the problem statement)
3. free(p); // the block at address 1314 is freed, but the variable p still stores 1314
4. printf("%u", p); // prints the numeric contents of p interpreted as unsigned

Intermediate detail: No assignment like p = NULL is made, so the pointer still holds 1314. There is no dereference of p (which would be undefined behavior after free); only the pointer value is printed.

Why the correct answer is 1314:
- Because p still equals 1314 and the printf is asked to output that numeric value.

Why other options are incorrect:
- "-1314": negative value would require interpreting bits as a signed negative number; given the address 1314 this is not the case.
- "garbage (random) value": freeing memory does not randomize the pointer variable; it remains 1314 until changed.
- "0": free does not set the pointer to 0 (NULL) automatically.

Conclusion: The program will print 1314, which matches the provided correct answer.

What is the output (to stdout) of this C code, assuming all these lines will execute on the CPU uninterrupted? (assume p has address 1314)单项选择题

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