ios C++ programmatic breakpoints and stepping into C++ lambdas

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Created Sep ’16

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What call are you supposed to make for iOS breakpoints (f.e. assert). But I don't want asserts default behavior where it kills the thread, I want to be able step over erroneous asserts. In the past I've used sigtrap(). I've tried setsignal and the variants. I'm looking for the C or C++ equivalent of asm { int 3; } on Intel. I saw the XCode 8 is removing Debugger and DebugStr, but there's never been an alternative suggested on iOS.

Also how is it that Xcode is still unable to step into C++ 11 lambdas? There's XCode regex setting to ignore all of the ^std:: functions, but I should be able to step into lambda just like I can step into blocks. I can't see anyway to adjust the setting to let just lambda through. If I turn that off, then I'm stepping 10 levels into STL functions before I finally get to the lambda. This has to be provided by the debugger, not by developers.

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DTS Engineer OP

Apple

Sep ’16

What call are you supposed to make for iOS breakpoints (f.e. assert).

For debugging I recommend sending the

SIGTRAP

signal to yourself.

raise(SIGTRAP);

You’ll have to then step out of the

kill

system call, but that’s easy.

In production code, use

__builtin_trap

.

The difference is important.

__builtin_trap

has some key advantages in production:

It traps at the point of failure, meaning you’re more likely to have useful content in registers.
It is marked as ‘not returning’, which is more grist for the optimiser.

OTOH, when debugging it’s actually good to have avoid a ‘not returning’ mechanism because you actually want to step past the failure.

Also how is it that Xcode is still unable to step into C++ 11 lambdas?

You should watch WWDC 2016 Session 417 Debugging Tips and Tricks, which discusses some of the challenges in this space. Beyond that, for debugger specific issues I recommend you post over in Xcode > Debugger.

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