debugger unsync with code

Edited and built changes into the code does not show in the debugger.

What I do : 

Build project (cmake)

Run debugger (system lldb) with a breakpoint somewhere and wait for debugger to stop there. Stop debugger.

Edit the code around that location.

Build (only changes, not rebuild all).

re-run the debugger. Changes don't appear and the debugger sees the last version before edition.

Rebuilding all seems to solve the issue and changes appear. But I'm not positive that's always the case. Sometimes I need to erase the build dir. Sometime restarting QTC seemed enough...

I'm using

/Applications/Xcode.app/Contents/Developer/usr/bin/lldb --version
lldb-1103.0.22.4
Apple Swift version 5.2 (swiftlang-1103.0.32.1 clang-1103.0.32.29

cmake version 3.16.5

clang version 9.0.1

all my changes are made in CPP header files

quite annoying.