Totalview® for HPC User Guide : PART II Debugging Tools and Tasks : Chapter 8 Setting Action Points : Setting Breakpoints and Barriers : Setting Breakpoints on Classes and Functions : Setting Machine-Level Breakpoints
Setting Machine-Level Breakpoints
To set a machine-level breakpoint, you must first display assembler code. You can now select an instruction. TotalView replaces some line numbers with a dotted box ()—this indicates the line is the beginning of a machine instruction. If a line has a line number, this is the line number that appears in the Source Pane. Since instruction sets on some platforms support variable-length instructions, you might see a different number of lines associated with a single line contained in the dotted box. The icon appears, indicating that the breakpoint occurs before the instruction executes.
If you set a breakpoint on the first instruction after a source statement, however, TotalView assumes that you are creating a source-level breakpoint, not an assembler-level breakpoint.
Figure 104 – Breakpoint at Assembler Instruction
If you set machine-level breakpoints on one or more instructions generated from a single source line, and then display source code in the Source Pane, TotalView displays an icon (Figure 88) on the line number. To see the actual breakpoint, you must redisplay assembler instructions.
When a process reaches a breakpoint, TotalView does the following:
• Suspends the process.
• Displays the PC arrow icon () over the stop sign to indicate that the PC is at the breakpoint.  
Figure 105 – PC Arrow Over a Stop Icon
• Displays At Breakpoint in the Process Window title bar and other windows.
• Updates the Stack Trace and Stack Frame Panes and all Variable windows.
 
RELATED TOPICS 
 
Displaying assembler code
Barrier points