Mixing C and C++ in Lab Projects

Why Use C and C++ Together?

In this course, we use a C/C++ mixed programming style to make the code modular, maintainable, and scalable.

C++ allows us to structure code using object-oriented programming (OOP) — for example, defining reusable classes such as Button, Timer, or Sensor.
C remains the language of the TivaWare and Texas Instruments peripheral drivers (like driverlib, grlib, or Crystalfontz display libraries).

Fortunately, C++ is backward-compatible with C, meaning you can call C functions from C++ — if you handle the compiler linkage correctly.

What Is Name Mangling?

When a C++ compiler builds code, it performs name mangling — it changes function names internally to include extra information such as parameter types and namespaces.

For example:

// Original C++ function
int add(int a, int b);

Might be compiled internally as something like:

_add_int_int

This helps C++ support function overloading, but it causes problems when linking with pure C code, since C compilers don’t mangle function names.

So if your project mixes both languages, the linker won’t find matching symbols unless you tell it which functions should use C-style naming.

Using `extern "C"` to Prevent Linker Errors

To ensure that your C libraries compile correctly inside a C++ project, you must wrap them with the extern "C" block:

// ===== Include C driverlib headers (wrapped in extern "C" for C++ builds) =====
extern "C" {
#include "driverlib/fpu.h"
#include "driverlib/sysctl.h"
#include "driverlib/interrupt.h"
#include "driverlib/timer.h"
#include "inc/hw_memmap.h"
#include "Crystalfontz128x128_ST7735.h"
#include "grlib/grlib.h"
#include "sysctl_pll.h"
}

// ===== Custom helper libraries =====
#include "button.h"       // Physical button FSM + debounce
#include "timerLib.h"     // Hardware timer wrapper
#include "elapsedTime.h"  // millis-style elapsed time utilities

This block tells the compiler:

“Treat everything inside as C code, not C++ code.”

That way, all Texas Instruments libraries — which are written in pure C — link correctly with your C++ source files.

Library Protection (Already Included)

The libraries provided for this course already include this protection internally. That means:

You don’t need to add extern "C" around our custom libraries (button.h, timerLib.h, etc.).
You must still wrap Texas Instruments’ driver and hardware headers inside an extern "C" block whenever you include them in a .cpp file.

Summary

Type of Code	Example Files	Needs `extern "C"`?
TI Drivers / HAL	`driverlib/`, `grlib/`, `Crystalfontz128x128_ST7735.h`	✅ Yes
Custom Course Libraries	`button.h`, `timerLib.h`, `elapsedTime.h`, `HAL_TM4C1294XL.h`	❌ No
Your Application Code	`main.cpp`, `lab0.cpp`	❌ No