Debug of program exit

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Debug of program exit

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oaf
Contributor IV

In my world I don't use exit() at all, but sometimes a nasty error could happen inside a library func

which calls exit(). In the comp.c this function is implemented as this:

void _exit(int status)

{

// disable all interrupts, run infinite loop

    __asm("cpsid i");

    while(1);

}

What would be much nicer is if the sw could just enter the debugger. Do I have to patch the source, or is there a

non intrusive way of do this?

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marek_neuzil
NXP Employee
NXP Employee

Hello,

I have checked the source code file and it is located in KSDK_1.1.0\rtos\mqx\mqx\source\psp\cortex_m\compiler\gcc_arm\comp.c, i.e. this program module is a part of MQX. It is a static source code file and you can modify it.

    

This issue is related to MQX software solution. I will move it.

Best Regards,

Marek Neuzil

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marek_neuzil
NXP Employee
NXP Employee

Hello,

I have checked the source code file and it is located in KSDK_1.1.0\rtos\mqx\mqx\source\psp\cortex_m\compiler\gcc_arm\comp.c, i.e. this program module is a part of MQX. It is a static source code file and you can modify it.

    

This issue is related to MQX software solution. I will move it.

Best Regards,

Marek Neuzil

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oaf
Contributor IV

Ok,

If I may wish a solution with a function-pointer, weak-link would be better, as you then doesn't have to change the library source.

BTW:what is the assembly instruction for breakpoint?

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DavidS
NXP Employee
NXP Employee
   __asm("bkpt 4"); //DES example of using assembly code in "C" source to halt/break in the code.  A debugger can then step over and the resume execution.

Regards,

David

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jvasil
Contributor III

In some example code, I've seen this coded with a '0' instead of a '4'.  ARM documentation says:

"The BKPT instruction causes the processor to enter Debug state. Debug tools can use this to investigate system state when the instruction at a particular address is reached.

In both ARM state and Thumb state, imm is ignored by the ARM hardware. However, a debugger can use it to store additional information about the breakpoint." [ARM Information Center]

So I'm curious if there is any particular reason for using '4'?

I'm also curious about what happens if a bkpt instruction is executed when there is no debugger connected.  I assume this acts similar to either a NOP or a HALT but haven't found a description of this yet.

Thanks,

James

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DavidS
NXP Employee
NXP Employee

Hi James,

No particular reason for "4" other than it works.

My testing without debugger has behavior of a HALT.

Regards,

David

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jvasil
Contributor III

Thanks.  Just FYI, '0' seems to work too.  Guess you COULD look at this value to take some action in the debugger.

Too bad about the behavior--guess that means can't leave bkpt instructions sprinkled in the code!!

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