C/C++: Passing a structure by value, with another structure as one of its members, changes values of this member's members.

Question

Sorry for the confusing title, but it basically says it all. Here's the structures I'm using (found in OpenCV) :

struct CV_EXPORTS CvRTParams : public CvDTreeParams
{
    bool calc_var_importance;
    int nactive_vars;
    CvTermCriteria term_crit;

    CvRTParams() : CvDTreeParams( 5, 10, 0, false, 10, 0, false, false, 0 ),
        calc_var_importance(false), nactive_vars(0)
    {
        term_crit = cvTermCriteria( CV_TERMCRIT_ITER+CV_TERMCRIT_EPS, 50, 0.1 );
    }
}

and

typedef struct CvTermCriteria
{
    int    type;
    int    max_iter;
    double epsilon;
}
CvTermCriteria;

CV_INLINE  CvTermCriteria  cvTermCriteria( int type, int max_iter, double epsilon )
{
    CvTermCriteria t;

    t.type = type;
    t.max_iter = max_iter;
    t.epsilon = (float)epsilon;

    return t;
}

Now, I initialize a CvRTParams structure and set values for its members :

 CvRTParams params;
 params.max_depth = 8;
 params.min_sample_count = 10;
 params.regression_accuracy = 0;
 params.use_surrogates = false;
 params.max_categories = 10;
 params.priors = priors;
 params.calc_var_importance = true;
 params.nactive_vars = 9;
 params.term_crit.max_iter = 33;
 params.term_crit.epsilon = 0.1;
 params.term_crit.type = 3;

Then call a function of an object, taking params in as a parameter :

CvRTrees* rt = new CvRTrees;
rt->train(t, CV_ROW_SAMPLE, r, 0, 0, var_type, 0, params);

What happens now ? Values of...

params.term_crit.max_iter
params.term_crit.epsilon
params.term_crit.type

have changed ! They are no longer 33, 0.1 and 3, but something along the lines of 3, 7.05541e-313 and 4, and this, for the whole duration of the CvRtrees::train() function...

Answer 1

By the time I finished writing this question I found the answer. So I figured I'd post anyway if someone comes across the same problem. The code itself wasn't wrong (or at least, it wasn't completely wrong). However I am using MacOS X and apple-gcc on a ppc processor (G5). I was using the -fast flag for optimization. Removing the -fast flag (leaving only -O3) solved the problem.