There are two ways to import linker-defined symbols into your C or C++ source code. Use either:

extern unsigned int symbol_name;

or:

extern void *symbol_name;

If you declare a symbol as an int, then you must use the address-of operator to obtain the correct value as shown in Example 4.2.

extern unsigned int Image$$ZI$$Limit
config.heap_base = (unsigned int) &Image$$ZI$$Limit