GDB Breakpoints are inaccurrate on Mac

Question

I have been using gdb on Mac recently but sometimes the breakpoints are wrong such that if I assign a breakpoint and run gdb sometimes skips the breakpoint or breaks on the wrong line. Can anyone help me out? I've tried to find the simplest case of the issue below.:

Project
|
+-- CMakeLists.txt
|    
+-- include
|    |  
|    +-- A.hpp
|
+-- src 
     |  
     +-- main.cpp

A.hpp

#pragma once

class A { 
public: 
   A(const char* t){};
}; 

main.cpp

1 #include<string>
2 #include"A.hpp"
3 int main(){ 
4   std::string s = "";
5   A a = "";
6   return 0;
7 }

CMakeLists.txt

1 cmake_minimum_required (VERSION 3.0)
2
3
4 file(GLOB SOURCES "src/*.cpp")
5 set(CMAKE_BUILD_TYPE Debug)
6 
7 add_executable(main ${SOURCES})
8
9 target_include_directories(main PUBLIC include)

If I try to set a breakpoint in main.cpp line 4 where the string is assigned and run main in gdb, it stops on line 5. I think that this happens when standard headers like are used. If I change line 4 to a simple assignment like int i = 0;, the breakpoint stops on line 4 as expected.

I Have:

Mac Version High Sierra 10.13.6

CMakeVersion: 3.12.0

GDB version: 8.0.1 (installed via homebrew)

Thanks for any help in advance.

Answer 1

gdb sometimes skips the breakpoint or breaks on the wrong line

In general, this happens when the code is built with optimizations.

I know you've selected CMAKE_BUILD_TYPE Debug , but perhaps that is still doing an optimized build for some reason?