In my program I can (or should be able to) change the slave the master works with by commenting in or out calls to the function 'purchase' with different slave addresses as parameter:

//	purchase(SLAVE_1);
purchase(SLAVE_2);
//purchase(SLAVE_3);  // not useable at the moment
//purchase(SLAVE_4);  // not useable at the moment
//purchase(SLAVE_5);  // not useable at the moment
 

In this case the master is calling up SLAVE_2 at line masterBackChat::400.  In the function purchase the slave actually being called is checked by

			if (memcmp(slave, SLAVE_1, 5) == 0)
			{
			  slave1purchased = true;
       if (debug) Serial.println("Purchasing SLAVE_1");
			}
      
			if (memcmp(slave, SLAVE_2, 5) == 0)
			{
			  slave2purchased = true;
       if (debug) Serial.println("Purchasing SLAVE_2");
			}
 

at line masterBackChat::720.

My problem is that on several occasions building and running the program calling SLAVE_2 results in it persisting in calling SLAVE_1 still.  This occurs in VS and also in the Arduino IDE.  It is sporadic, and currently it has corrected itself.

Has anyone ever heard of this trick?
If so, what did you find caused it?

Thanks

Okay.  Fair enough.

It's actually a compiler problem - not code.
https://1drv.ms/i/s!ArMxdUYEh9fKgWlbJ1NxnNIxnmqq

I can't see how you can build something which specifically uses one parameter and it compiles with another.  When I was a kid compilers did not work like that!

The call to 'purchase' is at masterBackChat::408 and the debug output line is at masterBackChat::572.

I have attached the image in case the inclusion does not work.

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:44am:
 

Sorry.  The size of that got a bit out of hand.  Hope this is better.
https://1drv.ms/i/s!ArMxdUYEh9fKgWlbJ1NxnNIxnmqq

line 399 on the left is the call to the function 'purchase' with the parameter SLAVE_1.  On the right you see the COM6 printout showing that the parameter actually compiled was SLAVE_2 !  As I said, in the good old days compilers didn't do that.  To make matters worse, it's sporadic.  Sometimes it happens, sometimes it doesn't. 

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:44am:


The source code was attached to the original post as 'backchat.zip'.

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:44am:


The relevant code lines are listed in my last post.

Thanks for showing an interest.  I have never seen this sort of behaviour when compiling/building a program.

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


I agree with you.  I have been using GCC as a compiler since before we had IDEs.  It's a rock!

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


No

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


I image was programming the master code and, yes, it is connected to COM6 because the COM6 printout shows what it is trying to do (and the lights on the Adruino UNO flash when it is uploading).


Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


Yes because at least it tried to work and that showed up on the COM6 printout.

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


Done

Tim@Visual Micro wrote on Feb 28^th, 2017 at 11:54pm:


See attached.  I'll have to do another post to send you the current code.   

I agree that there is something other than the compiler doing this, and my chief suspect is the addresses used.  I can get my master to work with SLAVE_1 but and (sometimes) with SLAVE_2, but trying to get it to work with both creates chaos.  That is why the current code has optional sets of addresses (I comment them in and out as I try things).

By the way, what do you press to build ad upload?

If there isn't any confusion over which project you are building and upload then I would be looking at memcmp as the culprit. But as I have said arduino.cc are the best people to help with code.

const uint8_t SLAVE_0[] = { 0xAA, 0xAA, 0xAA, 0xAA, 0xAA };
const uint8_t SLAVE_1[] = { 0xBB, 0xBB, 0xBB, 0xBB, 0xBB };
const uint8_t SLAVE_2[] = { 0xCC, 0xCC, 0xCC, 0xCC, 0xCC };

void setup()
{
   purchase(SLAVE_2);
}

void purchase(const uint8_t* slave)
{
  if (memcmp(slave, SLAVE_1, 5))
		Serial.println("Purchasing SLAVE_1");

  if (memcmp(slave, SLAVE_2, 5))
		Serial.println("Purchasing SLAVE_2");
} 

other things to look for at times like this. 

make sure you haven't got any stray code files in the project folder that are not included in the project. If you have then remove them or include them in the visual studio project.

look in the build folder that is shown in the verbose build output and see what actual code has been compiled in the project_name.cpp. The project_name.cpp in the build folder should contain a copy of the code from the .ino file(s) of the project. That will be the last code that was compiled. If that matches your expected code then the issue is code.

Thanks. I will leave you to study your code. Maybe use a simpler check to compare which slave is current