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From: Lucretia <Lucretia9000@yahoo.co.uk>
Newsgroups: comp.lang.ada
Subject: How do I disable elaboration code on this
Date: Sat, 9 Apr 2011 06:58:00 -0700 (PDT)
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Date: 2011-04-09T06:58:00-07:00
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The following code will not compile no matter what I do. Basically, I
want to write the startup code for Cortex-M3 in Ada with no assembly.
So, the ISR code needs to be elaboration free as it's the first bit of
code that would run on reset.

Essentially, at address 0 the exception vectors are stored. These are
in flash ROM so elaboration code is out of the question anyway. Each
element of the array is a pointer to an interrupt service routine.
I've specified a 4 element vector to test this out:

I've compiled with:

~/opt/tamp/bin/arm-none-eabi-gnatmake --RTS=/home/laguest/src/mine/
tamp/rts/boards/xpresso1769 -c -g -gnatyy -gnaty-s -mcpu=cortex-m3 -
mthumb -gnatG test.adb

and used my own build of the compiler and my own zero footprint
runtime.

I get the following output:

-- Start of output
Source recreated from tree for ISR (body)
-----------------------------------------


package body isr is

   procedure isr__dummy is
   begin
      %push_constraint_error_label ()
      %push_program_error_label ()
      %push_storage_error_label ()
      null;
      %pop_constraint_error_label
      %pop_program_error_label
      %pop_storage_error_label
      return;
   end isr__dummy;
begin
   null;
end isr;

Source recreated from tree for ISR (spec)
-----------------------------------------

pragma restrictions (no_elaboration_code);
with system;
with system;
isr_E : boolean := false;

package isr is
   procedure isr__dummy;
   pragma convention (c, isr__dummy);
private
   type isr__cb is not null access procedure;
   pragma convention (c, isr__cb);
   type isr__vectors is array (1 .. 4) of isr__cb;
   pragma convention (c, isr__vectors);
   isr__addr : constant system.system__address := system__address!(
     0);
   [type isr__TvectorsB is array (1 .. 4 range <>) of isr__cb]
   freeze isr__TvectorsB [
      procedure isr__TvectorsBIP (_init : in out isr__TvectorsB) is
         %push_constraint_error_label ()
         %push_program_error_label ()
         %push_storage_error_label ()
         subtype isr__TvectorsBIP__S4s is isr__TvectorsB (_init'first(
           1) .. _init'last(1));
      begin
         for J1 in _init'first(1) .. _init'last(1) loop
            [constraint_error "access check failed"]
            _init (J1) := null;
         end loop;
         %pop_constraint_error_label
         %pop_program_error_label
         %pop_storage_error_label
         return;
      end isr__TvectorsBIP;
   ]
   [subtype isr__T12s is isr__TvectorsB (1 .. 4)]
   reference isr__T12s
   reference isr__T12s
   isr__vector : constant isr__vectors := (isr__dummy'access,
     isr__dummy'access, isr__dummy'access, isr__dummy'access);
   pragma convention (c, isr__vector);
   for isr__vector'address use isr__addr;
end isr;

isr.ads:20:04: violation of restriction "NO_ELABORATION_CODE" at line
1
arm-none-eabi-gnatmake: "isr.adb" compilation error
-- End of output

I've also tried an array of addresses, this produces the same problem.
Can anyone point me in the right direction? Surely, this is possible
in Ada?

-------------------------- Code below
--------------------------------------
pragma Restrictions (No_Elaboration_Code);

with System;

package ISR is
   procedure Dummy;
   pragma Convention (C, Dummy);
private
   type Cb is not null access procedure;
   pragma Convention (C, Cb);

   type Vectors is array (1 .. 4) of Cb;
   pragma Convention (C, Vectors);

   Addr : constant System.Address := System'To_Address
(16#0000_0000#);

   Vector : constant Vectors :=
     (Dummy'Access,
      Dummy'Access,
      Dummy'Access,
      Dummy'Access);
   pragma Convention (C, Vector);
   for Vector'Address use Addr;
end ISR;
package body ISR is
   procedure Dummy is
   begin
      null;
   end Dummy;
end ISR;
pragma Restrictions (No_Floating_Point);

with ISR;

procedure Test is
begin
  null;
end Test;