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Mac Forum / Programming / CodeWarrior / January 2004Can't set breakpoints at certain lines
I have noticed that there are certain lines in my code which are being called yet do not have the little dashes next to them which enable me to set breakpoints on that code. For example: unsigned long test_date = 0; //***** Search the read array for the oldest message for (i = 0; i < MAX_INPUT_MESSAGES; i++) { test_date = message_array[i].date_time; if (test_date < oldest_date) { oldest_date = message_array[i].date_time; index = i; } } In this bit of code I cannot set breakpoints at lines 1 or 6. Also "test_date" doesn't show up as a variable in the debugger even if I break at one of the other lines in the method. I've turned inlining off in the C language menu. I'm on Mac OSX. Thanks for any help. CT On 22/1/04 8:31 pm, in article cthomas-4BFEBC.14312722012004@teta.doit.wisc.edu, "Charles Thomas" <cthomas@REMOVE_SPAM_BLOCK.facstaff.wisc.edu> wrote: > I have noticed that there are certain lines in my code which are being > called yet do not have the little dashes next to them which enable me to [quoted text clipped - 26 lines] > > CT Inlining may be turned off, but what about your optimization level (under Code Gen/Global Optimization in the project's preferences). I don't claim to know the details, but I suspect at the level you've got, the compiler has optimized away some code, and perhaps used a register for test_date. Maybe. Steve. >I have noticed that there are certain lines in my code which are being >called yet do not have the little dashes next to them which enable me to [quoted text clipped - 22 lines] > >I'm on Mac OSX. I'd have to know more, for example what are lines 1 and 6 in the above example and optimizations It may be your code is not used and just dead stripped out for example index = i might or might not be stripped out. Ron  SignatureMetrowerks, maker of CodeWarrior - "Software Starts Here" Ron Liechty - MWRon@metrowerks.com - <http://www.metrowerks.com> > >For example: > > [quoted text clipped - 21 lines] > I'd have to know more, for example what are lines 1 and 6 in the above > example and optimizations. I'm not sure what you mean, Ron. Line 1: unsigned long test_date = 0; Line 6: test_date = message_array[i].date_time; > It may be your code is not used and just dead > stripped out Well, clearly it is being used since the variable is having a value assigned to it, then is being tested against the value of oldest_date. Perhaps I don't understand your definition of "not being used" in this context. CT >> >For example: >> > [quoted text clipped - 26 lines] >Line 1: unsigned long test_date = 0; >Line 6: test_date = message_array[i].date_time; I didn't know if you counted comments or blank lines. These lines have breakpoints for me. >> It may be your code is not used and just dead >> stripped out > >Well, clearly it is being used since the variable is having a value >assigned to it, then is being tested against the value of oldest_date. Not necessarily for example the compiler can see that your code does nothing but increment from zero to some number and skip all of the loops and just go to the last number. >Perhaps I don't understand your definition of "not being used" in this >context. it is optimized out and not used or isn't used period. Ron SignatureMetrowerks, maker of CodeWarrior - "Software Starts Here" Ron Liechty - MWRon@metrowerks.com - <http://www.metrowerks.com> >> > unsigned long test_date = 0; >> > [quoted text clipped - 8 lines] >> > } >> > } > >Well, clearly it is being used since the variable is having a value > >assigned to it, then is being tested against the value of oldest_date. > > Not necessarily for example the compiler can see that your code does > nothing but increment from zero to some number and skip all of the loops > and just go to the last number. I guess I'm just not following you. If the code is creating a variable test_date and assigning the value of message_array[i].date_time to it, then comparing that value to see if it's less than the value in the variable oldest_date, how can it be considered "not used"? Not only is it used, but the entire method fails if this comparison isn't done. CT >>> > unsigned long test_date = 0; >>> > [quoted text clipped - 20 lines] >then comparing that value to see if it's less than the value in the >variable oldest_date, how can it be considered "not used"? I'm talking generic and you are talking specifics which is why you may not be follwoing. However the point is if this has optimizations on, no matter what, processor scheduling, peephole etc then it may be optimized away, you can't do debugging and see every line if optimizations are on. >Not only is it used, but the entire method fails if this comparison >isn't done. OK suppose instead of test_date = message_array[i].date_time; if (test_date < oldest_date) you used if (message_array[i].date_time < oldest_date) I'm telling you that the compiler with optimizations on is smart enough to figure that out and make the substitution thereby making the first and sixth lines unused Ron SignatureMetrowerks, maker of CodeWarrior - "Software Starts Here" Ron Liechty - MWRon@metrowerks.com - <http://www.metrowerks.com> > >isn't done. > OK suppose instead of [quoted text clipped - 9 lines] > to figure that out and make the substitution thereby making the first > and sixth lines unused Ah, I see your point now. Thanks for clarifying. The reason I often use the more verbose method is *specifically* to debug those values while stepping through the code. If message_array isn't a variable local to the method in question there's no way to check its value as you're stepping through the code (it doesn't show up in the variable list of the debugger), so I create a local copy of it in the method to check the value during debugging. This used to be a good way to do this, but now with optimizations I've been outsmarted by the compiler! I guess I've not yet found all the places to turn off optimizations. I'll keep looking. CT >> >isn't done. >> OK suppose instead of [quoted text clipped - 25 lines] > >I'll keep looking. declare the variable volatile then it can't be optimized away. Ron SignatureMetrowerks, maker of CodeWarrior - "Software Starts Here" Ron Liechty - MWRon@metrowerks.com - <http://www.metrowerks.com> |
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