MATLAB: Is the memory alignment by mxCalloc and/or mxMalloc defined

MATLABmex

I want to create a MEX function for MATLAB 2014a which uses AVX intrinsics, and the memory used needs to be 32 byte aligned.
Looking at the documentation for the mex memory functions I can't see any specific alignment which is provided by mxCalloc or mxMalloc.
However, running the following example under MATLAB 2014a 64-bit in Linux:
#include <mex.h>
#include <matrix.h>
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    int len;
    void *data;
    size_t data_addr;
    size_t alignment;
      alignment = 0;
      for (len = 1; len < 0x10001; len++)
      {
          data = mxMalloc (len);
          data_addr = (size_t) data;
          alignment |= data_addr;
      }
      mexPrintf ("mxMalloc alignment=%lx\n", alignment); 
      alignment = 0;
      for (len = 1; len < 0x10001; len++)
      {
          data = mxCalloc (len, 1);
          data_addr = (size_t) data;
          alignment |= data_addr;
      }
      mexPrintf ("mxCalloc alignment=%lx\n", alignment); 
  }
Appears to show that the addresses returned by mxMalloc and mxCalloc have 32 byte alignment (in that the least significant 5 bits of the addresses are always zero):
>> mex c_align_test.c
Building with 'gcc'.
MEX completed successfully.
>> c_align_test
mxMalloc alignment=7f85ffffffe0
mxCalloc alignment=7f85ffffffe0
Is the guaranteed memory alignment provided by mxCalloc and mxAlloc documented anywhere?

Best Answer

This topic has come up in the past. I believe the MATLAB API functions use malloc & friends in the background, and those functions are required to return a pointer that is properly aligned for any typical object on the system you are running on. E.g., see a short discussion here:
http://stackoverflow.com/questions/3994035/what-is-aligned-memory-allocation
However, as is pointed out this requirement does not necessarily cover special cases, and your 32-byte alignment would probably fit into that category. I am unaware of any MATLAB documentation that discusses this level of detail to give you the warm fuzzy you want.
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