Blocks and block identifiers for C

It is often necessary to set breakpoints on entry into or exit from a given block or to reference variables that are not immediately visible from the current block. z/OS® Debugger can do this, provided that all blocks are named. It uses the following naming convention:

• The outermost block of a function has the same name as the function.
• For C programs compiled with the ISD compiler option, blocks enclosed in this outermost block are sequentially named: %BLOCK2, %BLOCK3, %BLOCK4, and so on in order of their appearance in the function.
• For C programs compiled with the DWARF compiler option, blocks are named in a non-sequential manner. To determine the names of the blocks, enter the DESCRIBE CU; command.

When these block names are used in the z/OS Debugger commands, you might need to distinguish between nested blocks in different functions within the same source file. This can be done by naming the blocks in one of two ways:

Short form

function_name:>%BLOCKzzz

Long form

function_name:>%BLOCKxxx :>%BLOCKyyy: … :>%BLOCKzzz

The currently active block name can be retrieved from the z/OS Debugger variable %BLOCK. You can display the names of blocks by entering:

DESCRIBE CU;