Select the true statement

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BlackTom AI · Accepted Answer

The prompt provided has no list of answer options to compare, so I’ll first note that the true assessment depends on the available choices. With the information shown, there is a statement: "We can call malloc and free in any function, as long as we eventually call free on that particular block of memory." Here’s how to reason about this concept in C:

- Core idea: malloc allocates a block of memory on the heap and returns a pointer. free releases that same block back to the heap. The critical constraint is ownership: each allocated block must be freed exactly once by some code that has access to the corresponding pointer.
- Calling malloc in any function: It is generally permissible to call malloc from any function, provided the resulting pointer is correctly propagated (passed as an argument, assigned to a global/static location, or otherwise accessible to the code that will eventually manage it).
- Freeing in a different function: It is also valid to free the memory in a different function than where malloc was called, so long as you still hold a valid pointer to the allocated block and you guarantee that free will be reached with that exact pointer, exactly once.
- Important caveats:
  • Do not free a pointer more than once. A duplicate free can lead to undefined behavior, crashes, or heap corruption.
  • Do not use a pointer after it has been freed (use-after-free). Accessing freed memory is undefined behavior.
  • Ensure that the memory allocated by malloc is actually freed before program termination to avoid leaks, unless the OS will reclaim it on exit (which is not reliable for long-running programs).
  • If malloc fails, it returns NULL. Always check for NULL before using the pointer, and handle the failure appropriately.
  • If ownership is unclear (e.g., multiple modules or threads), you must establish clear ownership semantics and synchronization to avoid double frees or leaks.
- Potential misconceptions:
  • Some students think you must free in the same function you malloced in. In reality, you can free in a different function as long as the pointer is valid and you free exactly once.
  • Another misconception is that you can never free memory allocated in one thread from another thread. Concurrent access to the same pointer requires proper synchronization, but freeing from another thread is not inherently prohibited—it depends on program design and concurrency controls.

In the absence of additional answer choices, this statement is broadly true in C semantics with the important caveats highlighted above: the key requirement is that each allocation is freed exactly once, and the pointer is valid at the time of free. Any option asserting that memory must be freed in the same function, or that freeing is optional, or that freeing can occur only in certain contexts without regard to ownership, would be misleading or incorrect.

COMP2017 COMP9017 (ND) inclass5w6P1

Select the true statement

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类似问题

Consider the function call: p = (data_t )malloc((num - 1) sizeof(data_t)) The intention of this function call is best described as:

Which header file must be included to use dynamic memory allocation functions like malloc and free?

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If the heap memory location starts at 9403, what is the value of the integer variable myAge at position 1? #include <iostream> using namespace std; int a = 10; int main() { int b; int* myAge = nullptr; b = 20; myAge = new int; // Position 1 *myAge = 30; delete myAge; return 0; }

What does the following code print?#include <iostream> using namespace std; int* allocateMemory() { int ptr = new int; ptr = 10; return ptr; } int main() { int p = allocateMemory(); cout << p << endl; delete p; return 0; }

Which of the following is the correct way to allocate memory dynamically for an integer type array of 10 elements.

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COMP2017 COMP9017 (ND) inclass5w6P1

Select the true statement

查看解析

登录即可查看完整答案

类似问题

Consider the function call: p = (data_t *)malloc((num - 1) * sizeof(data_t)) The intention of this function call is best described as:

Which header file must be included to use dynamic memory allocation functions like malloc and free?

The C realloc function is conventionally used to

If the heap memory location starts at 9403, what is the value of the integer variable myAge at position 1? #include <iostream> using namespace std; int a = 10; int main() { int b; int* myAge = nullptr; b = 20; myAge = new int; // Position 1 *myAge = 30; delete myAge; return 0; }

What does the following code print?#include <iostream> using namespace std; int* allocateMemory() { int *ptr = new int; *ptr = 10; return ptr; } int main() { int *p = allocateMemory(); cout << *p << endl; delete p; return 0; }

Which of the following is the correct way to allocate memory dynamically for an integer type array of 10 elements.

更多留学生实用工具

希望你的学习变得更简单

Consider the function call: p = (data_t )malloc((num - 1) sizeof(data_t)) The intention of this function call is best described as:

What does the following code print?#include <iostream> using namespace std; int* allocateMemory() { int ptr = new int; ptr = 10; return ptr; } int main() { int p = allocateMemory(); cout << p << endl; delete p; return 0; }