Re: tgmath.h

[David Brown]

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

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.)