Linker-defined Symbols

The linker-generated start and end symbols that are automatically generated for loadable segments are internal if they are addresses into internal segments, and external if they are for external segments. All other linker defined symbols you create in a LCF are considered external unless you redefine them with INTERNAL_SYMBOL . The linker also defines some linker defined symbols for its own use ( Linker-defined Symbols ).

Table 1. Linker-defined Symbols
Symbol Name	Value	Description
`_stack_addr`	top of the stack -	External. Comes from settings panel settings.
`_stack_end`	bottom of the stack	External. Comes from settings panel settings.
`_heap_addr`	bottom of the heap	External. Comes from settings panel settings.
`_heap_end`	top of the heap	External. Comes from settings panel settings.
`_SDA_BASE_`	`.sdata` + `0x00008000`	Internal per EABI requirement. May not be redefined.
`_SDA2_BASE_`	`.sdata2` + `0x00008000`	Internal per EABI requirement. May not be redefined.
`_ABS_SDA_BASE_`	`.sdata` + `0x00008000`	External version of _SDA_BASE_ that can be used as an absolute. May not be redefined.
`_ABS_SDA2_BASE_`	`.sdata2` + `0x00008000`	External version of _SDA2_BASE_ that can be used as an absolute. May not be redefined.
`_nbfunctions`	number of functions in program	Deprecated. External. This is a number, not an address. May not be redefined.
`SIZEOF_HEADERS`	size of the segment headers	External. This is a number, not an address. May not be redefined.

Note: The symbols _SDA_BASE_ and _SDA2_BASE are not accessible until the small data registers are properly initialized before being accessible. The symbols _ABS_SDA_BASE and _ABS_SDA2_BASE allow you to access those pointers as absolutes addresses, as it is difficult to initialize those pointers without accessing them as absolute addresses.

Note: The stack and heap linker generated symbols are external. It may be more practical in a SDA PIC/PID application to make the heap and stack be contiguous with an internal segment and define them as internal.