Re: [Axiom-developer] GCC/GCL warning messages

[Gabriel Dos Reis]

address@hidden writes:

| Camm,
| 
| I'm building the next Axiom release. During the GCL build I see a large
| number of messages that read:
| 
| gcl_defmacro.c:In function `L12':
| gcl_defmacro.c:79: warning: dereferencing type-punned pointer will
|  break strict-aliasing rules
| 
| C99 language semantics now assume that pointers to different types
| point to different memory locations, which is obvious nonsense, but
| part of the new standard.

That statement is obviously untrue. 

The non-aliasing rule, which has always been there since I don't know
when -- certainly, it is part of C89, and it is not a C99 invention --
says that the following is undefined behaviour

      double z;
      *(long*)&z = 1;
      printf ("%g", z);

That makes perfect sense.  Why would you think it is nonsense?

| You might want to add -fno-strict-aliasing option to the GCC command line.

Instead of papering over the incorrectness, I would suggest to fix it.

-- Gaby