Folks,
A few questions concerning desktop simulation. I tend to develop code in Linux, but most of the students on the team tend to use Windows.
We’ve had good luck porting our C++ code so far to the new Command API, and now with desktop simulation, which we’ve never used.
We use a NavX MXP for an navigation unit. When we added an AHRS instance in RobotContainer, it builds fine for RoboRio, both Windows and Linux (makes sense, as they should be using the same cross-compiler). However, for desktop simulation, it builds fine under Windows, but does not link in Linux.
I’m wondering: Is this due to the GNU gcc compiler being a little more strict than Microsoft’s C++ compiler? Of is it another reason?
Here is the error we are getting on Linux:
RobotContainer.o: In function `RobotContainer::RobotContainer()':
RobotContainer.cpp:37: undefined reference to `AHRS::AHRS(frc::SPI::Port)'
collect2: error: ld returned 1 exit status
Here’s code excerpts:
RobotContainer.h:
// The header for the NavX MXP AHRS class
#include "AHRS.h"
...
class RobotContainer {
...
private:
// Declare a pointer to an AHRS system, using the NavX MXP
AHRS* m_AHRS;
...
}; // end class RobotContainer
RobotContainer.cpp:
#include "RobotContainer.h"
...
// The constructor for the robot container
RobotContainer::RobotContainer() : m_autonomousCommand(&m_subsystem) {
// Initialize all of your commands and subsystems here
m_AHRS = new AHRS(k_navx_mxp_imu_port);
// Configure the button bindings
ConfigureButtonBindings();
} // end RobotContainer::RobotContainer()
...
From what I can tell, there is no way to wrap the offending code in C++ like one can in Java with RobotBase.isReal(), per the WPILib docs. For C++, the only recommendation is using pointers, which we did above.
The only alternative I see would be to use a pre-processor directive, i.e.
#if !SIMULATING
// Initialize all of your commands and subsystems here
m_AHRS = new AHRS(k_navx_mxp_imu_port);
#endif
Any recommendations for that?
Also, one other question/comment: In the WPILib docs:
C++ robot simulation requires that a native compiler to be installed. For Windows, this would be Visual Studio 2019 (not VS Code), macOS requires Xcode, and Linux (Ubuntu) requires the build-essential package.
It would be helpful to explain in the docs what part of Visual Studio 2019 is needed. We downloaded Visual Studio 2019 Community Edition, and installed the “Desktop Development with C++” workload. It seemed to work. Should that choice work? Hopefully teams understand that Community Edition is free, but Professional and Enterprise is not.
It appears Xcode for macOS is also free. And of course, the build-essential package is free as well.
And as always, thank you for any help!
Details:
WPILib: v2020.3.2
KauaiLabs_navX_FRC: v3.1.413
gcc: gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0