Hi,
Arduino is a non-standard mix of C and C++, of undocumented (AFAIK)
version, with an IDE that automates and hides some features (such as
some headers). They use their own special libraries, and an older
version of avr-gcc that has a number of non-conformities. (Of
particular relevance here, it has 32-bit "double" instead of 64-bit.)
You cannot achieve your aims here with a single code base that works on
Arduino tools and also on, say, a PC platform for simulation, and gives
the same results.
You can do a /lot/ better if you use modern versions of avr-gcc as
"normal" tools and drop the Arduino stuff.
You can also do better if you code to a common subset of C99 and C++
(whatever version Arduino uses) - that means dropping <tgmath.h> and
replacing it with <math.h> with explicitly named functions for different
sized parameters. Alternatively, use a common C++ subset and drop the
C99 requirements (again, dropping <tgmath.h>, replacing it now with
<cmath>).
There's a lot to like with Arduino - its relatively easy to use, and
there is a lot of sample code and tools that let you get proof of
concepts working quickly. But it has its disadvantages, and its
non-standard language and oversimplification of the underlying compiler
is a problem for more advanced usage.
David
On 26/04/2022 14:20, Ivan Perez wrote:
Thanks!! This is very helpful!
The hope is to generate the same C99 code regardless of the platform. So
we need to use a math library that will work across platforms and
deliver consistent behaviour.
Ivan
On Fri, Apr 22, 2022 at 5:22 AM David Brown <david.br...@hesbynett.no
<mailto:david.br...@hesbynett.no>> wrote:
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.)
