[lldb-dev] Hiding trampoline functions from the backtrace, is it possible ?

Nat! via lldb-dev lldb-dev at lists.llvm.org
Tue Sep 24 11:36:12 PDT 2019

On 24.09.19 19:28, Jim Ingham wrote:
> We've had many requests to elide some classes of entries in backtraces - like to mirror the Xcode display I mentioned previously.  Most of these requests don't depend on the functions being marked artificial.  So if we're going to do this, something more general than just "marked artificial" -> elided anyway.
> Jim


Having done a little further research... Artificial won't work for 
general cases anyway, since it's restricted to inline code (for some 
reason) on gcc and clang. I wonder why, since for a function the only 
real effect is to emit DW_AT_artificial (AFAIK). The restriction seems 
arbitrary and DWARF wouldn't mind.. But the compilers do, so it seems 
out anyway.

DW_AT_trampoline isn't supported by llvm. As I read the description of 
DW_AT_trampoline, its more like a hardcoded vector (a->b), so not useful 
for cases like objc_msgSend, where you don't know the destination a priori.

If I look at the DWARF spec, I don't see any other way to mark a 
function as "boring". I still think this would be a good thing, as this 
would be useful for other debuggers as well, which could instantly work. 
Also a lot of code in the lldb Trampoline classes, for step-in and 
step-out could probably just be removed.


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