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Re: Type Alignment
Jeff Squyres wrote:
> Here's what we need:
>
> 1. What is a reliable / correct test to determine the alignment of a
> Fortran type? (I don't care a whit about the previous tests -- if
> they're wrong, we'll throw them out)
Portably, there isn't. Fortran doesn't make any guarantees. I believe for
gfortran they will always be the same as for gcc, but a middleend or backend
person would have to verify this.
> 2. Will this alignment be the same between compatible Fortran 77 and
> Fortran 90 compilers? (e.g., compilers of the same vendor/version,
> or, in a trivial case, using the same "gfortran" to compile f77 and
> f90 compilation units)
Yes, it's the same compiler after all.
> 3. Am I reading these replies correctly that the *alignment* of a
> type may change depending on whether a derived type is sequenced or
> not? I can understand how members might be re-ordered in memory by
> the compiler (and that's not a problem for us), but can it really
> change the datatype's alignment? If so, this could be a Big Problem
> for us.
In principle yes. Again, the Fortran standard doesn't make any guarantees
about this.
- Tobi