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Re: -malign-double switch patch?


On Sunday, 11 August 2002 13:11, Jamie Lokier wrote:
> Nix wrote:
> > > Apparently you didn't read the documentation, in which it is said
> > > that the switch affects the abi, and therefore should be used
> > > only with extreme caution under controled conditions.
> >
> > GCC-3.1.x's manual says
> >
> > ,----
> >
> > | `-malign-double'
> > | `-mno-align-double'
> > |      Control whether GCC aligns `double', `long double', and
> > | `long long' variables on a two word boundary or a one word
> > | boundary. Aligning `double' variables on a two word boundary will
> > | produce code that runs somewhat faster on a `Pentium' at the
> > | expense of more memory.
> >
> > `----
> >
> > i.e., it doesn't mention the ABI breakage :( perhaps this is only
> > in the trunk...
>
> The next paragraph says:
>
>      *Warning:* if you use the `-malign-double' switch, structures
>      containing the above types will be aligned differently than the
>      published application binary interface specifications for the
> 386.

No it doesn't. The next paragraph is the description of the 
-m128bit-long-double option, which does have a warning similar to that.
But there's nothing to indicate that the same warning applies to 
-malign-double. (This is in the 3.1 docs; as Nix said, the current 
development version may have something different.)

-- 
Ross Smith ..................................... Auckland, New Zealand
r-smith@ihug.co.nz ...................................................

        "A specter is haunting Wall Street; it is the specter
        of honest accounting."           -- Arthur D. Hlavaty


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