On 22/04/2022 02:18, Ivan Perez wrote:

I'm trying to compile a program for arduino that relies on tgmath.h to pick the right version of a function based on the types (the code is automatically generated by another tool).

It's failing to compile with avr because tgmath.h is missing.

I thought it was part of the standard C distribution since C99 and thus I'd be able to rely on it, but I'm no C expert. Does anyone know why it is not included in avr-libc? Any advice?

I'm on Ubuntu 20.04, using:
avr-libc 2.0.0+Atmel3.6.2-1.1
gcc-avr 5.4.0+Atmel3.6.2-1
binutils-avr 2.26.20160125+Atmel-3.6.2-2



You are right that <tgmath.h> has been part of C since C99. But it is not part of C++, which is what the Arduino tools use. <tgmath.h> has macros for type-generic maths functions, and was originally implemented with compiler-specific extensions. With C11, the "_Generic" feature can be used to make compiler-independent implementations of the functions. In C++, function overloading has existed from the beginning, and is done in a completely different way. (Indeed, <tgmath.h> in C was invented to give C programmers the convenience C++ users already enjoyed for their maths functions, but made in a C-style manner.)

So for your C++ code, you should use <cmath>, not <tgmath.h>, and otherwise the usage will be the same. (You might need a "using namespace std;", but the Arduino IDE likes to confusingly hide such detail.)

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