mxGetPr inside mexFunction returning null

i have a mexFunction() which i compile under visual studio.

inside the mexFunction() i have sometthing like

 double *a = mxGetPr(nrhs[1]);

 the complilation is fine and in the debug mode i am able to enter the mexFunction and stop at the "double *a" line but i get null for "a".

i am unable to figure out what the problem may be. For a different program similar procedures work.

Answer 1

[Jan]

"I have something like" is not sufficient for a question. Obviously there is a problem with the specific code, therefore posting something similar cannot help to find the bug.

mxGetPr(prhs[1]) works correctly, whenever the function was called with at least 2 inputs and the 2nd one is a double array. Is this the case?

[EDITED] James saw, that "nrhs" is wrong here and "prhs" must be meant.

[Kaushik]

mxGetPr(nrhs[1]) was the only thing that was inside the mexFunction(). I was trying to see whether the pointer is read correctly. I found that mxGetPr(nrhs[1]) is not working if i have "#include mclmcrrt.h". When I comment out the mclmcrrt.h header mxGetPr(nrhs[1]) starts returning non-null pointers.

[James Tursa]

I am assuming that nrhs[1] is a typo and should be prhs[1] ... true? And as Jan has already said, please post your code instead of making us guess with your code snippets. Also post how you are calling the function from the m-file level.

[Jan]

@James: Oh. I've overseen the obviously confused "nrhs" and "prhs". It was almost midnight and one of the hottest nights we can have in central Europe.