I use 64-bit Windows and have sufficient physical memory to benefit considerably from doing so. But, when compiling many *nix-developed code(*), for 64-bit, I encounter myriad warnings and some outright errors, because of the difference between the compilation data models used by the two platforms.

Specifically,

• *nix uses the LP64 data model where shorts and ints are 32-bit; and both longs and pointers are 64-bit.

  This allows pointers to be assigned to ulongs without loss.

• Win64 uses the LLP64 data model where shorts, ints and longs are 32-bit; and longlongs and pointers are 64-bit.

  Pointers cannot be assigned to longs without loss.

Regardless of the wisdom or superiority of one choice over the other, the situation exists and has to be lived with. Currently:

• Perl compiles (with scads of warnings) using 64-bit; and runs mostly without problem.

  Though I've seen a couple of failures that might be attributable to incompatibnility. But they only occor once Perl starts getting close to 4GB barrier and by that time it is already into swapping. Clear diagnosis is impossible due to the system running like a dog.

• Parrot builds at 64-bit (with scads of warnings), but fails (preotection violation) to build its own runtime.

I've been looking into what it would take to try and fix-up the warnings for Perl64. The problem lies in the pervasive assumption that a pointer will fit in a long. Ostensibly, the fix is define any typedef or variable that must accept a pointer as a long long rather than a long, but it is never quite that simple.

So, to the question.

Does anyone know of any good discussion/wisdom/examples of coding for LP64 .v. LLP64 portability?

(*)To give topical reference: Perl and Parrot suffer this.

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