Delphi: why breakpoints from time to time are not usable (green highlighted line on IDE)?

Question

From time to time I lose breakpoint functionality in Delphi.

I thought this to be a Delphi 2009 issue but now I have also it in Delphi XE.

In Delphi 2009 by

Answer 1

Since this is the best resource I found on this issue when encountering this problem with a new install of Delpi XE on a new laptop, I will just add in one more possible answer for Delphi XE.

If you are using a two monitor setup and the code editor window is on the 2nd monitor, the tooltips will not show. Works fine if the editor window is on the primary monitor. Very frustrating. May be a driver issue.

Answer 2

I found a better way.

From the Project Manager tree, right click on the project and choose "Clean" from the popupmenu.

The breakpoints reappear magically and it is a very fast method.

Answer 3

I suspect this happens when you have done a release build, with debug disabled. Then you switch back to debug configuration and do a compile rather than a build. The files where you can't set breakpoints correspond to those with DCUs produced by a compile with debug disabled.

Simply doing a build to re-generate all DCU files will make your breakpoints work again.

Answer 4

In delphi 7 there seems to be a real bug on setting breakpoints.

I had a unit where many texts are definied in a

const constname : array[0..x] of record-type = (...);

in interface section, where record-type has some AnsiString items. In the implementation section there are some procedures.

In some particular cases, when I set a breakpoint anywhere within a procedure, delphi does not stop at it!

Remarks: all options for debugging are set properly (as for F7 causes delphi stop at the "begin" of the program, blue dots are visible in the whole unit the line stays red while executing the app) and all DCUs that have according PAS files were deleted from all of my disks and within all folders, before I did a complete build on the whole project. So no wold files should hang around anywhere. For testing, I renamed the PAS to another name, never ever used before, and surely nowhere else on any disk, then adapted all sources and recompiled, just to be sure that delphi and I are looking at the same PAS file - but the breakpoints did not work either.

But there another, very weird thing happened: the text consts (!) changed within my executable (not within exe file, but obviously within memory)! Those texts were checked for correctness during program start, and sometimes it complained about errors! Display of the texts in a messagebox showed, that there was changed a sinlge character within that texts, that are defined as const. For test, I tried to assign something to that consts within my code, but, as expected, compiler complained, so it cannot be an ordinary assignment that causes the change of the text. Must be a wrong pointer. Weird.

So, hours of testing followed, looking for any source code that might have set up a wrong pointer that later could cause that change in a text const. I placed the messagebox into the initialization section of the first unit within the chain of unit initialization I was able to edit, but the changed char was already there! Must be changed very early during startup of my application, then!

Finally I figured out, that the char that appeared in my texts always was an $CC - which exactly is the assembler code for INT 3, the code that delphi is using for setting a breakpoint. And when moving a breakpoint within that unit a line up or down, the position of the changed character also moves some chars left or right! And the number of characters the wrong one moved just correlated with the estimated amount of assembler coded bytes the concerned lines needed. Setting two breakpoint in lines near each other, suddenly two characters changed! When removing all breakpoints from that unit, the text remained unchanged!

So there's only one conclusion: delphi itself is changing that texts when trying to set a breakpoint and fails to do so. I was unable to get rid of this bug. None of the tips about re-synching delphi's internal bookkeeping of source and object code files did help me out!

As the concerned unit mainly consisted of {$I} lines between multiple {$IFDEF}s, for including some different, but long pascal texts, I considered delphi having problems on too long inclusions or on evaluation of conditional compiler directives. So I removed the includes and put the source text immediately into the unit, and removed the {$IFDEF}s - which compiled without errors, but setting breakpoints also changed my text constants, instead of stopping execution. All the same!

I solved this for now by splitting the unit into two units, one holding just the text consts in it's interface part, and a second one to hold the procedures. And now, without changing any compiler nor linker settings, all breakpoints do work like expected and not text is changed any more!

So, if breakpoints do not work for you, while you are sure they should, possibly delphi is the culprit and fails to set the breakpoints at the correct place. In case of it is changing just some texts, maybe that never gets to your attention. Splitting the unit helped me out, maybe that helps you, too.

Answer 5

By using F9 to run the app, breakpoints will work as expected. I am using XE4 and I do not know if this will "fix" prior versions of Delphi.

Answer 6

Debug info isn't present in the file.

Make sure that you're using the Debug configuration. (Project Manager tree, expand Build Configurations, make sure Debug is bold. If it's not, right click Debug and choose Activate from the context menu.) Make sure you then do a Build of your project, not just a Compile.

If that still doesn't work, go to Project->Options from the IDE's main menu, click on Compiling under Delphi Compiler, and check the Debugging section on the right half of the window. Make sure that Debug Information and Local Symbols are both checked. If you're trying to trace into the VCL's own source, also check Use debug .dcus (you'll want to turn this off and do a full build of your project as soon as you're done, as it gets annoying when you're debugging normally). Again, you'll want to build and not compile.

If all of the above fails, another possibility is that the code unit you have open in the Code Editor isn't the same one being seen by the compiler. Make sure you don't have multiple copies of the file on your computer in a location that the compiler might find first. If you're not sure, delete the .dcu files with that unit name and then do a build of your project, and see if the newly created .dcu is in the location you'd expect.