Sue Sue -4 years ago 176
C Question

How to reset static variables within a function

Is there a way to reset variables declared as static within a function? The goal is to make sure that the function is not called with lingering values from an unrelated call. For example, I have a function opearting on columns of a matrix.

int foo(matrix *A, int colnum, int rownum){
static int whichColumn;
static int *v; //vector of length A->nrows
if (column != whichColumn){
memset(v,0,size);
whichColumn = which;
}
//do other things
}


The function is called n times, once for each column. Is this a proper way of "re-setting" the static variable? Are there other general fool-proof ways of resetting static variables? For example, I want to make sure that if the call is made with a new matrix with possibly different dimensions then the vector v is resized and zeroed etc. It seems the easiest way may be to call the function with a NULL pointer:

int foo(matrix *A, int colnum, int rownum){
static int whichColumn;
static int *v; //vector of length A->nrows
if (A == NULL){
FREE(v);
whichColumn = 0;
}
//do other things
}

Answer Source

I'd recommend turning it into a struct and writing a small helper function for managing the semantics of what you're trying to do. It could return the buffer if the request is appropriate for its size, or create a new one on demand (and free the old one) if necessary.

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