18.2.16 Symbols Required by Start-Up Code and C/C++ Library
This section details the symbols that are required by the start-up code and C/C++ library. Currently the default device-specific linker script defines these symbols. If an application provides a custom linker script, the user must ensure that all of the following symbols are provided in order for the start-up code and C library to function:
| Symbol Name | Description |
|---|---|
_bmxdkpba_address |
The address to place into the BMXDKPBA register if
_ramfunc_length is greater than 0. |
_bmxdudba_address |
The address to place into the BMXDUDBA register if
_ramfunc_length is greater than 0. |
_bmxdupba_address |
The address to place into the BMXDUPBA register if
_ramfunc_length is greater than 0. |
_ebase_address |
The initialization value for the ExceptionBase field of the
EBASE register. The ExceptionBase is the base
address for the exception vectors, adjustable to a resolution of 4
Kbytes. The default device-specific linker scripts provided with the
XC32 toolchain provide a default location for the ExceptionBase. |
_end |
The end of data allocation. |
_gp |
Points to the “middle” of the small variables region. By convention this is 0x8000 bytes from the first location used for small variables. |
_heap |
The starting location of the heap in DRM. |
_ramfunc_begin |
The starting location of the RAM functions. This should be located at
a 2K boundary as it is used to initialize the BMXDKPBA
register. |
_ramfunc_length |
The length of the .ramfunc section. |
_stack |
The starting location of the stack in DRM. Remember that the stack grows from the bottom of data memory so this symbol should point to the bottom of the section allocated for the stack. |
_vector_spacing |
The initialization value for the vector spacing field in the
IntCtl register. |