Accessing Non-Scalar Arrays with ceval

2 views (last 30 days)
I'm trying to use the Matlab "mat" and "mx" C-libraries to use .mat-files inside of a Matlab function I'm compiling with the Matlab Coder. I can do this successfully for a scalar variable, but I'm having trouble getting non-scalar arrays in. Because coder.ceval can only return a scalar, my best guess of how to do this at the moment is to use the C "memcpy" function with a coder.wref input.
Here's what I've got right now, referencing a .mat-file "testmat.mat" that has one variable in it, a 1x4 double:
y = ones(1,4);
SS_Table_File = coder.opaque('MATFile *');
rr = ['r',char(0)];
SS_Table_file = coder.ceval('matOpen','testmat.mat',rr);
Xp = coder.opaque('mxArray *');
XX = ['X',char(0)];
Xp = coder.ceval('matGetVariable',SS_Table_file,XX);
yp = coder.opaque('double *');
yp = coder.ceval('mxGetPr',Xp);
This currently compiles OK but then produces a segfault (or some other fatal error that crashes Matlab) when I run it.

Accepted Answer

Greg on 13 Jun 2012
Apparently the above code would actually work OK if size_t were a 32-bit integer (which I had assumed it was). On my 64-bit linux machine that defines size_t as an unsigned long int (a uint64), I have to do something like this since the Matlab coder doesn't support 64-bit integers:
sz = coder.opaque('size_t');
sz = coder.ceval('(size_t)',4*8);

More Answers (0)


Find more on MATLAB Coder in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!