mxMalloc returns 0xffffffffe03c9460 which I cannot access

Hey there,

I use the NURBs-Toolbox and there are two options, 1 is to use Matlab Files, which is slow but works and the second is use C-Files:

So the Toolbox is about 10 years old, so this could be a problem. If I run the mex-files I get segfaults. So I tried to debug them and the fault is always the same: mxMalloc returns a pointer with 0xffffffff and then something. And then I can't access this array.

double *left = (double*) mxMalloc((p+1)*sizeof(double));

Is the call. The initializing fails, if mxMalloc returns an address at the end of the 48bit area.

I run Ubuntu 10.10 64bit with 64bit Matlab R2010b. Do i compile the files the wrong way or do I have to make some changes because of 64bit pointers?

Thanks

Philipp

Answer 1

[Philipp H]

#include "mex.h"

was missing. I feel silly.

Thanks

[Jan]

Impressive! The compiler does not show any warnings and is able to compile the file?! Which compiler do you use?

[James Tursa]

Likely OP just made function calls w/o any special types used in the code (e.g., mwSize etc.). So the missing prototypes for mxMalloc etc would just generate ("assuming int return" etc) warnings and not errors.

Answer 2

[Jan]

Storing the result of an mxMalloc call in an "int" can fail on 64-bit machines: The replied value has 64 bits, the "int" has 32 bits only - usually.

So be sure to use 64 bit variables whenever it is necessary: most of all mwSize, mwIndex, mwSignedIndex are helpful. I've seen an example here, where "ptrdiff_t" helped: Answers: BLAS in mex files

[Philipp H]

double *left = (double*) mxMalloc((p+1)*sizeof(double));

This is the Call. Should have posted this earlier. If I initialize the left[0] I get the Segfault.

Thanks.