Semaphore in Ada - embedded

Question

This is an assignment and I have been asked to implement a Semaphore in Ada as the description below.
However I have implemented the Semaphore.adb and called this Semaphore in the producerconsumer_sem.adb which I created.
I get some output which is the following.
I'm not sure if my initialization of semaphore is correct S: CountingSemaphore(1,1);.
I don't know where I call the S.wait and S.Signal now i randomly called the S.wait before Producer put item in the buffer X := I; and the S.Signal after the X := I;.
Is this the correct way?
Producer-Consumer Problem
The program producerconsumer.adb implements a non-reliable implemen-
tation of the producer-consumer problem, where data is likely be lost. In
the following, you will use three different communication mechanisms to
achieve a reliable implementation of the producer-consumer problem.
Semaphore
The Ada language does not directly provide library functions for a semaphore.
However, semaphores can be implemented by means of a protected object. Create a package specification Semaphore in the file Semaphores.ads
and the corresponding package body in the file Semaphores.adb that
implements a counting semaphore. Skeletons for the package are available on the course page.
Use the semaphore package for a reliable implementation of the producer-
consumer problem. Modify the file producerconsumer.adb and save the
final code as producerconsumer_sem.adb. In order to use the semaphore
package it shall be installed in the same directory as producerconsumer_sem.adb.
It can then be accessed by
with Semaphores;
use Semaphores;
The Output:
OutPut:
1
1
1
2
2
3
4
4
5
6
6
7
7
8
9
9
9
10
11
11
11
12
12
13
13
13
14
15
15
16
16
17
18
18
18
19
20
20
21
21
22
22
23
24
24
24
24
25
25
26
27
27
28
29
29
30
30
31
31
32
32
33
33
33
34
35
35
35
36
36
37
37
37
38
38
38
39
40
40
40
The package
package Semaphores is
protected type CountingSemaphore(Max: Natural; Initial: Natural) is
entry Wait;
entry Signal;
private
Count : Natural := Initial;
MaxCount : Natural := Max;
end CountingSemaphore;
end Semaphores;
The Semaphore I implemented semaphores.adb.
package body Semaphores is
protected body CountingSemaphore is
entry Wait when Count > 0 is
begin
Count := Count - 1;
end Wait;
entry Signal when Count < MaxCount is
begin
Count := Count + 1;
end Signal;
end CountingSemaphore;
end Semaphores;
The producerconsumer_sem.adb
with Ada.Text_IO;
use Ada.Text_IO;
with Ada.Real_Time;
use Ada.Real_Time;
with Ada.Numerics.Discrete_Random;
with Semaphores;
use Semaphores;
procedure ProducerConsumer_sem is
X : Integer; -- Shared Variable
N : constant Integer := 40; -- Number of produced and comsumed variables
S: CountingSemaphore(1,1);
--S1: CountingSemaphore(1,1);
pragma Volatile(X); -- For a volatile object all reads and updates of
-- the object as a whole are performed directly
-- to memory (Ada Reference Manual, C.6)
--Random Delays
subtype Delay_Interval is Integer range 50..250;
package Random_Delay is new Ada.Numerics.Discrete_Random
(Delay_Interval);
use Random_Delay;
G : Generator;
task Producer;
task Consumer;
task body Producer is
Next : Time;
begin
Next := Clock;
for I in 1..N loop
-- Write to X
S.Wait;
X := I;
S.Signal;
--Next 'Release' in 50..250ms
Next := Next + Milliseconds(Random(G));
Put_Line(Integer'Image(X));
delay until Next;
end loop;
end;
task body Consumer is
Next : Time;
begin
Next := Clock;
for I in 1..N loop
-- Read from X
S.Wait;
Put_Line(Integer'Image(X));
S.Signal;
Next := Next + Milliseconds(Random(G));
delay until Next;
end loop;
end;
begin -- main task
null;
end ProducerConsumer_sem;

Answer 1

On macOS, with FSF GCC 7.1.0 and GNAT GPL 2017, I changed your Put_Lines to Puts and got pretty-much the answer you state in the question.
The question says to create Semaphore.ads, .adb. This will work on Windows, and may work on macOS, but won’t work on Linux, because of GNAT’s file naming convention (see the end of this; it’s a good idea to get into the habit of using lower-case file names).
If you want to ensure that only one task has access to X at a time, I don’t think there’s much wrong with your Wait, Signal calls, though when I put a delay 0.1 at the beginning of Producer, the first value output was 151619216 (because X isn’t initialized). However! if the point is to communicate one update to X at a time (as implied by the names producer/consumer), you should
initialize the semaphore with a count of 0 (and a max of 1). This makes it a binary semaphore.
in Consumer, Wait only (i.e. remove the Signal)
in Producer, Signal only (i.e. remove the Wait). Also, remove the Put to avoid confusion!