[Ada] Allow user-specified elaboration order constraints

This patch adds a new feature that allows the user to specify a particular
elaboration order for some or all library items in the program.

The following test should produce the following output:

Command line:

gprbuild -q -f -gnatE -g p-main.adb -bargs -l -felab-order.txt

elab-order.txt file:

-- This is the elaboration order:
    p (spec) -- Spec of p comes first.
    -- Then the spec of q, and so on:
    q (spec)

    r (spec)

    p (body)

    r (body)

    q (body)

    p.main (body)

ada.exceptions (spec) -- Predefined unit should be ignored.
no_such_thing (body) -- Nonexistent unit should be ignored.

Test output:

p (spec) <-- q (spec)
q (spec) <-- r (spec)
r (spec) <-- p (body)
p (body) <-- r (body)
r (body) <-- q (body)
q (body) <-- p.main (body)
"ada.exceptions%s": predefined unit ignored
"no_such_thing%b": not present; ignored

ELABORATION ORDER
   ada (spec)
   ada.characters (spec)
   ada.characters.handling (spec)
   ada.characters.latin_1 (spec)
   interfaces (spec)
   system (spec)
   system.address_operations (spec)
   system.address_operations (body)
   system.case_util (spec)
   system.case_util (body)
   system.img_int (spec)
   system.io (spec)
   system.io (body)
   system.parameters (spec)
   system.parameters (body)
   system.crtl (spec)
   interfaces.c_streams (spec)
   interfaces.c_streams (body)
   system.standard_library (spec)
   system.exceptions_debug (spec)
   system.exceptions_debug (body)
   system.storage_elements (spec)
   system.storage_elements (body)
   system.stack_checking (spec)
   system.stack_checking (body)
   system.traceback_entries (spec)
   system.traceback_entries (body)
   ada.exceptions (spec)
   system.soft_links (spec)
   system.unsigned_types (spec)
   system.img_uns (spec)
   system.val_lli (spec)
   system.val_llu (spec)
   system.val_util (spec)
   system.val_llu (body)
   system.val_lli (body)
   system.wch_con (spec)
   system.wch_con (body)
   system.wch_cnv (spec)
   system.wch_jis (spec)
   system.wch_jis (body)
   system.wch_cnv (body)
   system.wch_stw (spec)
   ada.exceptions.last_chance_handler (spec)
   ada.exceptions.last_chance_handler (body)
   ada.exceptions.traceback (spec)
   system.address_image (spec)
   system.bit_ops (spec)
   system.bit_ops (body)
   system.concat_2 (spec)
   system.concat_2 (body)
   system.concat_3 (spec)
   system.val_util (body)
   system.concat_3 (body)
   system.concat_4 (spec)
   system.concat_4 (body)
   system.concat_5 (spec)
   system.concat_5 (body)
   system.exception_table (spec)
   system.exception_table (body)
   ada.strings (spec)
   ada.strings.maps (spec)
   ada.strings.maps.constants (spec)
   interfaces.c (spec)
   system.exceptions (spec)
   system.exceptions (body)
   system.exceptions.machine (spec)
   system.assertions (spec)
   system.wch_stw (body)
   system.img_uns (body)
   system.img_int (body)
   system.assertions (body)
   system.exception_traces (spec)
   system.exception_traces (body)
   system.memory (spec)
   system.memory (body)
   system.standard_library (body)
   system.object_reader (spec)
   system.dwarf_lines (spec)
   system.secondary_stack (spec)
   interfaces.c (body)
   ada.strings.maps (body)
   system.soft_links (body)
   ada.characters.handling (body)
   system.secondary_stack (body)
   system.dwarf_lines (body)
   system.object_reader (body)
   system.address_image (body)
   ada.exceptions.traceback (body)
   system.traceback (spec)
   system.traceback (body)
   system.traceback.symbolic (spec)
   system.traceback.symbolic (body)
   ada.exceptions (body)
   p (spec)
   q (spec)
   r (spec)
   p (body)
   r (body)
   q (body)
   p.main (body)

Ada code:

with Q, R;
package body P is
   procedure P_Proc is
   begin
      null;
   end P_Proc;
end P;
package P is
   procedure P_Proc;
end P;
procedure P.Main is
begin
   null;
end P.Main;
with P;
package body Q is
   procedure Q_Proc is
   begin
      null;
   end Q_Proc;
end Q;
with P;
package Q is
   procedure Q_Proc;
end Q;
with P;
package body R is
   procedure R_Proc is
   begin
      null;
   end R_Proc;
end R;
with P;
package R is
   procedure R_Proc;
end R;

Tested on x86_64-pc-linux-gnu, committed on trunk

2017-01-12  Bob Duff  <duff@adacore.com>

	* binde.adb (Forced): New reason for a dependence.
	(Force_Elab_Order): Implementation of the new switch.
	* binde.ads: Minor comment fixes.
	* bindusg.adb: Add -f switch. Apparently, there was an -f switch
	long ago that is no longer supported; removed comment about that.
	* opt.ads (Force_Elab_Order_File): Name of file specified for
	-f switch.
	* switch-b.adb: Parse -f switch.

[Ada] Allow user-specified elaboration order constraints

Commit Message

Patch