int main () {
  int res = 0;
  res = (intptr_t)malloc(sizeof(1000)); // L1
  printf("res = %d\n", res);            // L2
  return res;
}

Compiled with -g, optionally -ffreestanding -fno-builtin.

Break point on L1 and step (command: s)
- program ends (with res printed).
- this is also observed for memmove, memcpy (on -ffreestanding -fno-builtin)

Break point on L2 and step (command: s)
- goes into printf.


Looks like a (somewhat tricky) feature tuned (whitelist) for libc? LLDB behaves like my expectation: step on L1 will stop at L2. DWARF debug info (lines) looks correct. 


Affects many versions of gdb/gcc. Reproduced on:

- 11.0.50.20201224-git (GCC 10.2.0)
- Ubuntu 9.2-0ubuntu1~20.04 (GCC 9.3)

Seems duplicate with #25565.