MLReleaseSymbol()

#include "mathlink.h"

/* read a symbol from a link and then release the memory to MathLink for deallocation */

void f(MLINK lp)
{
    char *sym;

    if(! MLGetSymbol(lp, &sym))
        { /* unable to read a symbol from lp */ }

    /* ... */

    MLReleaseSymbol(lp, sym);
}