Re: [csmith-project/csmith] 717b1c: Fixed a bug related to --no-math64 and --no-longlo...

[John Regehr <regehr@cs.utah.edu>]

Here's my problem with unions.  The standard says this:

"When a value is stored in a member of an object of union type, the 
bytes of the object representation that do not correspond to that member 
but do correspond to other members take unspecified values."

I think this means that if we have this union:

union {
  int x;
  float y;
} u;

we can't use the union to do type casting like this:

u.x = 3;
return u.y;

This creates a problem for us:

case 1: we follow the standard.  this is very boring.

case 2: We don't follow the standard and we do generate code that does 
type casts using unions.  I think compilers support this.  Now we have 
to know alignment and size information for the target platform.  This 
makes Csmith output non-portable in two ways.  First, it will be 
specific to that target.  Second, it won't conform to the standard.

John