gdb stepping

[Alexandre Constantino]

I may not have understood you correctly and be instead completely off the target over here, but I think you are mixing different things... C code and assembly code.
If you give a "next" or "step" instruction to GDB it executes a high-level language instruction.

In your example:
IdleTaskCycles++;
corresponds to 5 assembly instructions.
GDB sees 1 high-level instruction while BDI sees 5 assembly lines.

You can also use GDB in assembly mode and get the same low-level view than in BDI. To step one assembly instruction use "si" (step instruction).


On Sunday 02 March 2008, Leon Pollak wrote:
> Hello, all.
> 
> As the question may be a bit off-topic, I ask your pardon ahead.
> But it seems tome that this may be interesting to many embedded programmers.
> 
> Anyway, I am using the BDI2000  device for COP interface to the target and it 
> has additional option to see what is happening via the telnet interface.
> Using this interface I noticed the following:
> 
> The simplest operator IdleTaskCycles++ is translated by compiler into 5 
> assembler comands (with -O0):
> 
> 0x0002b4cc  _Thread_Idle_body+24    lis     r9,15
> 0x0002b4d0  _Thread_Idle_body+28    lwz     r9,-15912(r9)
> 0x0002b4d4  _Thread_Idle_body+32    addi    r0,r9,1
> 0x0002b4d8  _Thread_Idle_body+36    lis     r9,15
> 0x0002b4dc  _Thread_Idle_body+40    stw     r0,-15912(r9)
> 
> OK. Now, when, standing on this line (IdleTaskCycles++) I ask the gdp to 
> do "next" command, it does it as required, but the BDI shows me that it has 
> done 5 step commands!
> The same is with "step" command, which seems obvious.
> OK, now I put a break point on the next line - one start and one stop, and the 
> result much faster.
> 
> Assuming that most of us work with some kind of remote connection, you 
> understand that this takes 5 times slower to do a step!
> 
> What is the catch here? Why do the gdb uses such a strange technique?
> 
> Thanks.