Is delete[] equal to delete?

Question

IP_ADAPTER_INFO *ptr=new IP_ADAPTER_INFO[100];

if I free using

delete ptr;

will it lead to memory leak, if not t

Answer 1

Just an illustration of some "undefined" behaviors on certain OSes and compilers. Hope it could be helpful for people to debug their code.

Test 1

#include 
using namespace std;
int main()
{
  int *p = new int[5];
  cout << "pass" << endl;
  delete p;
  return 0;
}

Test 2

#include 
using namespace std;
int main()
{
  int *p = new int;
  cout << "pass" << endl;
  delete[] p;
  return 0;
}

Test 3

#include 
using namespace std;
struct C {
  C() { cout << "construct" << endl; }
  ~C() { cout << "destroy" << endl; }
};

int main()
{
  C *p = new C[5];
  cout << "pass" << endl;
  delete p;
  return 0;
}

Test 4

#include 
using namespace std;
struct C {
  C() { cout << "construct" << endl; }
  ~C() { cout << "destroy" << endl; }
};

int main()
{
  C *p = new C;
  cout << "pass" << endl;
  delete[] p;
  return 0;
}

• Windows 7 x86, msvc 2010. Compile with default options, i.e. exception handler is enabled.

Test 1

pass

Test 2

pass

Test 3

construct
construct
construct
construct
construct
pass
destroy
# Then, pop up crash msg

Test 4

construct
pass
destroy
destroy
destroy
destroy
destroy
destroy
destroy
... # It never stop until CTRL+C

• Mac OS X 10.8.5, llvm-gcc 4.2 or gcc-4.8 generate the same output

Test 1

pass

Test 2

pass

Test 3

construct
construct
construct
construct
construct
pass
destroy
a.out(71111) malloc: *** error for object 0x7f99c94000e8: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
zsh: abort      ./a.out

Test 4

construct
pass
a.out(71035) malloc: *** error for object 0x7f83c14000d8: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
zsh: abort      ./a.out

• Ubuntu 12.04, AMD64, gcc 4.7

Test 1

pass

Test 2

pass

Test 3

construct
construct
construct
construct
construct
*** glibc detected *** ./a.out: munmap_chunk(): invalid pointer: 0x0000000001f10018 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7eb96)[0x7fe81d878b96]
./a.out[0x400a5b]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7fe81d81b76d]
./a.out[0x4008d9]
======= Memory map: ========
....
zsh: abort (core dumped)  ./a.out

Test 4

construct
destroy
destroy
destroy
destroy
destroy
destroy
destroy
destroy
...
destroy
destroy
*** glibc detected *** ./a.out: free(): invalid pointer: 0x00000000016f6008 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7eb96)[0x7fa9001fab96]
./a.out[0x400a18]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7fa90019d76d]
./a.out[0x4008d9]
======= Memory map: ========
...
zsh: abort (core dumped)  ./a.out