lldb: Breakpoint on exceptions (equivalent of gdb's catch throw)

Question

I am trying to use lldb for c++ debugging and I want to halt if an exception is thrown, like gdb's catch throw, and I cannot find an equivalent in the lldb documentation.

Octarchy

Answer 1

In Xcode, you can set an Exception breakpoint (View > Navigators > Show Breakpoint Navigator, hit the + button in the bottom of the breakpoint list window to add a new breakpoint).

If you're using command line lldb, put a breakpoint on __cxa_throw for C++ exception throws, objc_exception_throw for Objective-C exception throws.

For all c++ exceptions: break set -E C++.

Joubert

for all c++ exceptions: break set -E c++ – Octarchy

ah, I missed the -E option to breakpoint set! Thanks for noting it. – Joubert

The '-F' and '-E' variants weren't working for me, but 'breakpoint -n __cxa_throw' did work (for all exceptions), as well as 'breakpoint -n <exception-name>' (for specific exceptions). – Handed

"-E objc" also works if you want Objective-C exceptions. – Metamorphic

break set -E c++ didn't work for me (perhaps because I'm using real GNU g++ instead of Apple's clang++?), but break set -n __cxa_throw did. @AnthonyHall's comment is lacking set. – Macaronic

I want to break immediately after throwing. break set -E c++ breaks on the rethrow statement. __cxa_throw works for me. Thank you. – Valvate

Answer 2

Use breakpoint set -E c++ to break on all exceptions and breakpoint set -F std::range_error to break on a specific exception.

Purposeful

I found that breakpoint set -F std::regex_error did not work for me. That does a full string match on function name and is thus fragile. However, breakpoint set -r regex_error, breaking on any function matching regex_error as a regex (targeting its constructor) did work. – Crescin

Answer 3

I think breakpoint set -w <boolean> is the correct answer, you can use help breakpoint set to see the document.

Toitoiboid

Answer 4

You can enter

breakpoint set -E c++

into LLDB to do this.

But if you want to configure LLDB to always do this, open ~/.lldbinit and put the same line into that file.

Parfitt