[Tinycc-devel] Tinycc issues

[Dominic Mazzoni]

Greetings to Fabrice Bellard et al.:

I just tried out tinycc for the first time and I'm very excited about its 
potential.  It exceeded all of my expectations in terms of compilation 
speed (more than 20x faster than gcc for my 10,000-line library) and the 
code it produces is pretty good.

My long-term interest in tinycc is for scientific programming; I think 
that libtcc could make a great just-in-time function compiler.  For now, 
though, I'm just experimenting with using it as a replacement for gcc for 
some of my existing numerical code.

Here are a couple of issues I ran into.  It is quite possible that some of 
these are due to ways that gcc differs from the C99 spec.  So I don't mean 
to imply that these are necessarily bugs in tinycc (except for one that 
causes tinycc to crash, see below) - perhaps they should just be known 
incompatibilities with gcc that could be listed somewhere.

1. NaN in floating-point constants:

   It is sometimes appropriate for a user-defined numerical function to
   return NaN.  Normally I do this by defining a constant in my code, like
   this:

     float NAN_FLOAT = (float)(0.0 / 0.0);

   Tinycc gives me the error message: "division by zero in constant".  To
   work around this, I tried to do it in two steps:

     float ZERO_FLOAT = (float)(0.0);
     float NAN_FLOAT =  (float)(ZERO_FLOAT / 0.0);

   This actually causes tinycc to crash.

2. Forward-declare arrays:

   With gcc, I am allowed to forward-declare an array of unspecified size,
   and then actually specify the size (implicitly) later in the code.  For
   example:

     int g_primes[];

     ...

     int g_primes[] = {2, 3, 5, 7, 11, 13, 17, 23};

   In tinycc, I get the error message: "unknown type size".

Thanks for listening!  I would be more than happy to send more information 
if you need it.

Regards,
Dominic