[m-rev.] diff: fix .module_dep files

[Julien Fischer]

On Tue, 22 Jul 2008, Jonathan Morgan wrote:

> On Tue, Jul 22, 2008 at 9:46 PM, Julien Fischer
> <juliensf at csse.unimelb.edu.au> wrote:
>>
>> On Tue, 22 Jul 2008, Zoltan Somogyi wrote:
>>
>>> On 22-Jul-2008, Peter Wang <novalazy at gmail.com> wrote:
>>>>
>>>> The recent renaming of the constructor `no_foreign_export' to
>>>> `contains_no_foreign_export' broke `.module_dep' files.  The offending
>>>> field
>>>> was written out directly with `io.write', so the renaming changed the
>>>> file
>>>> format, but the parser still expected the old spelling
>>>> "no_foreign_export".
>>>>
>>>> `mmc --make' would then try to remake all the `.module_dep' files it
>>>> couldn't parse, including modules whose source files we don't have at
>>>> hand.
>>>>
>>>> compiler/make.module_dep_file.m:
>>>>        Fix the bug.
>>>>
>>>>        Try to avoid a similar bug in another field.
>>>
>>> That looks great; thanks Peter. However, "grep -w io.write make*.m" gives
>>> five matches even after applying this diff. Will you please fix those as
>>> well?
>>> And does anyone else know of any other cases where the compiler is
>>> depending
>>> in the exact spelling of a function symbol to define part of a file
>>> format?
>>
>> Extending the above search to the all the compiler modules shows that we
>> are calling io.write in a bunch of other places as well, e.g. in ilasm.m
>> I think we should avoid calling it in the compiler except in debugging
>> code.  I suggest we add something along those lines to coding standard.
>
> I know the problems caused by io.write with formats changing, but I
> suspect that they don't apply to ilasm.  As far as I can tell, ilasm
> is using io.write for constants, string literals, and similar, all of
> which can save work without problems, since it is writing it out to an
> external format that isn't going to change on a whim.
>
> It seems to me that things like
>
> :- type call_kind
>    --->    default
>    ;       vararg
>    ;       unmanaged_cdecl
>    ;       unmanaged_stdcall
>    ;       unmanaged_thiscall
>    ;       unmanaged_fastcall.
>
> ...
>
> io.write(CallKind, !IO)
>
> make sense, since these types of things aren't ever going to change,

One change that may be made types like this is to add a prefix to
each constructor (this has been done for many other types in the
compiler in the recent past; it makes tools like mtags work
better).  Such a change applied here would break this code.

Julien.
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