Adding the following line to jconfig.h solved the problem.
#define USE_MAC_MEMMGR
In jmemmac.c, I found the following code which helped me to fix it. Just adding the above line worked!
#ifndef USE_MAC_MEMMGR /* make sure user got configuration right */
You forgot to define USE_MAC_MEMMGR in jconfig.h. /* deliberate syntax error */
#endif