On arm-none-eabi-gcc (cortex m0 / stm32f03), I see address values from Attribute'Address that seem to differ between those inserted at compile time and those which should be real. As an example, I look at the address of Hardfault_Handler.

This is my code:

 procedure Hardfault_Handler is
      SP : Address         := Get_Stack_Pointer; -- save sp after handler entry
      PC                 : Address := Get_Program_Counter; -- save current pc
      PC_Offset          : Storage_Offset  := PC - Hardfault_Handler'Address;
      Num_Of_Pushed_Regs : Natural         := 0;
      SP_Calc            : Integer_Address := To_Integer (SP);
      package Thumb_Ins_Pnt is new System.Address_To_Access_Conversions
        (Push_Instruction);
      use Thumb_Ins_Pnt;
      Temp_Ins : Object_Pointer;
   begin
      --loop over program code at start of hardfaulthandler
      for I in 0 .. PC_Offset when (I mod 2 = 0) loop
         Temp_Ins := To_Pointer (Hardfault_Handler'Address + I);
         -- is this a push instruction?
         if Temp_Ins.Mask = PUSH_Ins_Mask then
            -- yes, count number of regs we pushed to stack
            for Bit of Temp_Ins.Regs when Bit = True loop
               Num_Of_Pushed_Regs := Num_Of_Pushed_Regs + 1;
            end loop;
            -- alter back SP to Point before push (+ because stack grows down)
            SP_Calc := SP_Calc + 4 * Integer_Address (Num_Of_Pushed_Regs);

            declare
               Old_Regs : constant Stacked_Registers with
                 Import, Address => To_Address (SP_Calc + Stacked_Reg_Offset);
               Old_PC_Content : constant Thumb_Instruction with
                 Import, Address => Old_Regs.PC;
            begin
               if Old_PC_Content = Break_Point_Instruction then
                  -- Hardfault happend because no Debugger is connected,
                  -- just return
                  return;
               end if;
            end;
         end if;
      end loop;

      Put_Line ("Hard Fault");
      -- fault handling to be done
   end Hardfault_Handler;

Output of objdump:

 08000754 <m0__startup__hardfault_handler>:
   procedure Hardfault_Handler is
 8000754:       b5f8            push    {r3, r4, r5, r6, r7, lr}

   function Get_Stack_Pointer return Address is
      Result : Address;
   begin
      Asm
 8000756:       46ec            mov     ip, sp
   end Get_Stack_Pointer;

   function Get_Program_Counter return Address is
      Result : Address;
   begin
      Asm
 8000758:       467d            mov     r5, pc
      PC_Offset          : Storage_Offset  := PC - Hardfault_Handler'Address;
 800075a:       4e2a            ldr     r6, [pc, #168]  ; (8000804 <m0__startup__hardfault_h
andler+0xb0>)
   end "-";

Here the value for Hardfault_Handler"Address stored @8000804

    8000802:       bdf8            pop     {r3, r4, r5, r6, r7, pc}
 8000804:       08000755        stmdaeq r0, {r0, r2, r4, r6, r8, r9, sl}
 8000808:       08002a88        stmdaeq r0, {r3, r7, r9, fp, sp}
 800080c:       7fffffff        svcvc   0x00ffffff
 8000810:       0000beab        andeq   fp, r0, fp, lsr #29
 8000814:       08002a28        stmdaeq r0, {r3, r5, r9, fp, sp}
 8000818:       08002ad8        stmdaeq r0, {r3, r4, r6, r7, r9, fp, sp}

from inside gdb it looks like this:

also this is my vector table, the addresses are different too. But the reset handler, gets called and runs fine :

 Vector_Table : constant Address_Array :=
     (Sram_Stack_Start, Reset_Handler'Address, NMI_Handler'Address,
      Hardfault_Handler'Address, MemManage_Handler'Address,
      Bus_Fault_Handler'Address, Usage_Fault_Handler'Address, Reserved,
      Reserved, Reserved, Reserved, SVCall_Handler'Address,
      Debug_Handler'Address, Reserved, PendSV_Handler'Address,    
      Systick_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address, Default_Handler'Address,
      Default_Handler'Address);
   --Default_Handler'Address);
   pragma Linker_Section (Vector_Table, "_vector_table");

08000000 <m0__startup__vector_table>:
 8000000:       20001000        andcs   r1, r0, r0
 8000004:       080005b1        stmdaeq r0, {r0, r4, r5, r7, r8, sl}
 8000008:       08000699        stmdaeq r0, {r0, r3, r4, r7, r9, sl}
 800000c:       08000755        stmdaeq r0, {r0, r2, r4, r6, r8, r9, sl}
 8000010:       080006b1        stmdaeq r0, {r0, r4, r5, r7, r9, sl}
 8000014:       080006c9        stmdaeq r0, {r0, r3, r6, r7, r9, sl}
 8000018:       080006e1        stmdaeq r0, {r0, r5, r6, r7, r9, sl}
        ...

080005b0 <Reset_Handler>:

   -------------------
   -- Reset_Handler --
   -------------------

   procedure Reset_Handler is
 80005b0:       b570            push    {r4, r5, r6, lr}
      Data_L : Storage_Element with
        Volatile, Import, External_Name => "__data_size";

      Data_Length : constant Storage_Offset := Addr2SO (Data_L'Address);

      Data_Load_Array : Storage_Array (1 .. Data_Length) with
 80005b2:       4c16            ldr     r4, [pc, #88]   ; (800060c <Reset_Handler+0x5c>)
      Bss_L : Storage_Element with
        Volatile, Import, Convention => Asm, External_Name => "__bss_size";

Can someone explain this behavior?