-fdump-ada-spec

-fdump-ada-spec

[Simon Wright]

Does anyone know where this is implemented in the GCC sources?

I'm having trouble with some of the system headers: on Mac OS X, with
all the GNATs and GCCs I have, dumping /usr/include/wchar.h uses
'limited with' in a way that doesn't work, whereas on Debian (wheezy,
gcc-4.7) there's no 'limited with'. Of course, wchar.h is different!

I _think_ that -fdump-ada-spec sees that a particular type (eg FILE) is
always accessed via a pointer, and decides that 'limited with' is OK;
but for some reason this ends up being unacceptable.

The ARM (and AI95-0217) didn't help a lot here. I think the problem is
that the original code is like

   typedef struct Blah {
     int x;
   } FILE;

and the generated code is like

   package Stdio is

      type Blah is record
         X : Integer;
      end record;

      subtype FILE is Blah;

   end Stdio;

   limited with Stdio;
   package Wchar is

      procedure Foo (F : access Stdio.FILE);

   end Wchar;

and the 'limited with' magic only works for _types_, so you get the
error '"FILE" not declared in "Stdio"'.

Stdio.FILE should be declared as

      type FILE is new Blah;

Re: -fdump-ada-spec

[Stephen Leake]

Simon Wright <simon@pushface.org> writes:

> Does anyone know where this is implemented in the GCC sources?

I don't; I guess you want to develop a patch?

>  <snip>
>
> and the 'limited with' magic only works for _types_, so you get the
> error '"FILE" not declared in "Stdio"'.
>
> Stdio.FILE should be declared as
>
>       type FILE is new Blah;

As a workaround, you can maintain a patch for the generated code, and
apply it in your Makefile.

-- 
-- Stephe

Re: -fdump-ada-spec

[Markus Schöpflin]

Am 06.10.2014 19:45, schrieb Simon Wright:

> Does anyone know where this is implemented in the GCC sources?

The patch implementing -fdump-ada-spec can be found here: 
https://gcc.gnu.org/ml/gcc-patches/2010-04/msg01592.html

The diff should give you a precise idea where to look. :-)

Markus

Re: -fdump-ada-spec

[Simon Wright]

Stephen Leake <stephen_leake@stephe-leake.org> writes:

> Simon Wright <simon@pushface.org> writes:
>
>> Does anyone know where this is implemented in the GCC sources?
>
> I don't; I guess you want to develop a patch?

Not really; just to understand it better!

For example, you may have taken the online manual's remark "C++ classes
will be mapped to Ada tagged types" as gospel; it turns out that this
only happens for C++ classes with virtual methods. I think.

>>  <snip>
>>
>> and the 'limited with' magic only works for _types_, so you get the
>> error '"FILE" not declared in "Stdio"'.
>>
>> Stdio.FILE should be declared as
>>
>>       type FILE is new Blah;

Thinking about it, that doesn't match the 'semantics' of typedef.

> As a workaround, you can maintain a patch for the generated code, and
> apply it in your Makefile.

Actually, an editor script to change 'limited with' to plain 'with'
would sort this one out nicely.

Re: -fdump-ada-spec

[Simon Wright]

Markus Schöpflin <no.spam@spam.spam> writes:

> Am 06.10.2014 19:45, schrieb Simon Wright:
>
>> Does anyone know where this is implemented in the GCC sources?
>
> The patch implementing -fdump-ada-spec can be found here:
> https://gcc.gnu.org/ml/gcc-patches/2010-04/msg01592.html
>
> The diff should give you a precise idea where to look. :-)

Thanks!

Re: -fdump-ada-spec

[Simon Wright]

Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

>> Apparently one should use g++ rather than gcc, because it makes a better
>> job of it.
>>
>> GNAT GPL 2014 does translate (some) macros; it doesn't always get it
>> right, eg
>>
>>    #define M_SQRT2     1.41421356237309504880168872420969808   /* sqrt(2)        */
>>    #define M_SQRT1_2   0.707106781186547524400844362104849039  /* 1/sqrt(2)      */
>>    #define MAXFLOAT    0x1.fffffep+127f
>>
>>    // have to have _something_ besides the constants or no .ads gets
>>    // generated.
>>    extern float sinf(float);
>>
>> turns into
>>
>>    pragma Ada_2005;
>>    pragma Style_Checks (Off);
>>
>>    with Interfaces.C; use Interfaces.C;
>>
>>    package math_h is
>>
>>
>>       M_SQRT2 : constant := 1.41421356237309504880168872420969808;  --  ./math.h:1
>>       M_SQRT1_2 : constant := 8#.707106781186547524400844362104849039#;  --  ./math.h:2
>                                 ^^                                     ^
>
> Isn't that a blatant bug?  Either in the Ada or in the C source?

Yes; like I said, it doesn't always get it right.

And it doesn't understand hex floats either: 16#1.fffffep+127f# is *not*
a good translation of 0x1.fffffep+127f !

I have reported these problems to AdaCore, but as they have always said
the translation isn't expected to be perfect, so it'll be very low on
their priority list.

Re: -fdump-ada-spec

[Simon Wright]

Simon Wright <simon@pushface.org> writes:

> I'm having trouble with some of the system headers: on Mac OS X, with
> all the GNATs and GCCs I have, dumping /usr/include/wchar.h uses
> 'limited with' in a way that doesn't work, whereas on Debian (wheezy,
> gcc-4.7) there's no 'limited with'. Of course, wchar.h is different!

I'm told that this falls under "this capability is not intended to
generate 100% correct Ada specs".