Random C++ execution flow when using breakpoints in Visual Studio 2017?

I added breakpoints to every line in visual studio 2017 community edition for the following code

#include "pch.h"
#include <iostream>
using namespace std;

// base class
class Vehicle
public:
Vehicle()

cout << " **** This is a Vehicle **** " << endl;

;

// sub class derived from two base classes
class Car : public Vehicle

;

// main function
int main()

// creating object of sub class will
// invoke the constructor of base classes
Car obj;
return 0;



An action is set here to print a debug text when each line is executed.

I build the program then I ran a new debug instance. I got this

Output #1 : first 7 lines

main function
class car
blank line inside car class
// sub class derived
vehicle class closed
blank line after car class
// main


Then I rebuild the program and ran a new instance and I got this

Output #2: first 7 lines

main function bracket open
// main
car class close
class car
blank line inside car class
blank line after car class
blank line after vehicle class


I have optimization turned off.

I'm new to C++ and would like to know why this is happening, Is it compiling differently or is there something wrong with the breakpoint action execution?

EDIT: I have added the first 7 lines of the output in the screenshot. There you can see that the order of execution of the breakpoint action is different for the two runs.

NOTE: Please note that the output lines you see are added by me using the breakpoint -> action functionality, this way Visual studio will print out my message when that breakpoint is hit. The execution won't stop it will just print out whatever text I put in as the breakpoint action

1 Answer
1

You have breakpoints at many lines that do not actually represent executable code. When the application is executed, these breakpoints are moved to the closest executable statement.

You can see that when you actually break at a breakpoint in Visual Studio. Some of the breakpoints seem to be gone, but several breakpoints just moved to reference the same statement.

For the breakpoints that are moved to reference the same statement, the order of their debug messages is not defined.

Editor View:

Debugger view:

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