Compiler error (2) ?

[reinert]

Hello,

This must reveal a compiler error :
-------------------------------------------------------------------------------------------------------
with Ada.Text_IO;
with Ada.Containers.Vectors;
procedure test1a is
type s_name_type is (s0, s1, s2, s3, s4, s5, s6, s7, s8, s9);
for s_name_type use
(S0 => 0, S1 => 1, S2 => 2, S3 => 3, S4 => 4,
S5 => 5, S6 => 6, S7 => 7, S8 => 8, S9 => 9);
package s_names_p is new Ada.Containers.Vectors
(Index_Type => Positive, Element_Type => s_name_type);
k : integer := 7;

-- n : constant integer := 7; -- uncomment this line and comment out the line below.
n : constant integer := k;

s_names: constant s_names_p.Vector := [for i in 3..n => S0];
begin
Ada.Text_IO.Put_Line(s_names'Image);
end test1a;
-------------------------------------------------------------------------------------------------------
(compiled using alire and
package Compiler is
for Switches ("ada") use ("-gnatwa", "-gnata", "-gnatX", "-gnatwv");
end Compiler;
-------------------------------------------------------------------------------------------------------

Right?

reinert

[Simon Wright]

I'm not sure what compiler error you mean.

Agreed that the code as stands reports a strange issue,

11. S_Names: constant S_Names_P.Vector := [for I in 3..N => S0];
|
>>> error: expected type "Standard.Integer"
>>> error: found type "Ada.Containers.Count_Type"

which does look like a compiler error (even if it's only misreporting a
valid issue, I'm not sure).

What's more interesting is what happens if you make your suggested
change and it compiles. When you run it,

$ ./reinert_2

raised CONSTRAINT_ERROR : test1a.s_names_p.Replace_Element: Index is
out of range

Running this under the debugger, with 'catch exception',

Catchpoint 1, CONSTRAINT_ERROR (test1a.s_names_p.Replace_Element: Index is out of range) at 0x0000000100008ae5 in test1a () at reinert_2.adb:15
15 s_names: constant s_names_p.Vector := [for i in 3..n => S0];

So, what's Index?

(gdb) p index
No definition of "index" in current context.

Looing at the backtrace,

(gdb) bt
[...]
#4 0x0000000100011711 in test1a.s_names_p.replace_element (container=...,
index=6, new_item=s0)
at /opt/gcc-12.1.0/lib/gcc/x86_64-apple-darwin15/12.1.0/adainclude/a-convec.adb:2522
#5 0x0000000100008ae5 in test1a () at reinert_2.adb:15

Frame 4 is in the runtime; maybe we can see what's going on,

(gdb) fr 4
#4 0x0000000100011711 in test1a.s_names_p.replace_element (container=...,
index=6, new_item=s0)
at /opt/gcc-12.1.0/lib/gcc/x86_64-apple-darwin15/12.1.0/adainclude/a-convec.adb:2522
2522 raise Constraint_Error with "Index is out of range";
(gdb) p index
$1 = 6

Hmm. What does the source say?

(gdb) l
2517 is
2518 begin
2519 TE_Check (Container.TC);
2520
2521 if Checks and then Index > Container.Last then
2522 raise Constraint_Error with "Index is out of range";
2523 end if;
2524
2525 Container.Elements.EA (Index) := New_Item;
2526 end Replace_Element;

So Index (6) is more than Container.Last:

(gdb) p container
$2 = (elements => 0x600000008000, last => 5, tc => (busy => 0, lock => 0))
(gdb)

6 is certainly more than 5. Where does 5 come from?

Index is Positive. We were hoping to have our container with indices
supporting values up to 7, but the first index of a container has to be
Index_Type'First i.e. 1; the compiler has looked at the length of the
aggregate (5) and created an empty Vector s_names of that length.

Clearly you can't do slices in this context!

[J-P. Rosen]

Please give the exact error message, and why you think it could be a
compiler error. Otherwise, it's hard to help...

--
J-P. Rosen
Adalog
2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX
Tel: +33 1 45 29 21 52
https://www.adalog.fr

[reinert]

This is what I (also) get:

test1a.adb:16:42: error: expected type "Standard.Integer"
test1a.adb:16:42: error: found type "Ada.Containers.Count_Type"

compilation of test1a.adb failed

gprbuild: *** compilation phase failed
error: Command ["gprbuild", "-s", "-j0", "-p", "-P", "/home/reinert/test1a/test1a.gpr"] exited with code 4
error: Compilation failed.
---------------------------------------------------------------------------------------------------
**However, the following version goes through the compiler and runs
(using "subtype n_t is Positive range 3..Positive'Last;" for)

in the package specification) - confirming what Simon says:

with Ada.Text_IO;
with Ada.Containers.Vectors;
procedure test1a is
type s_name_type is (s0, s1, s2, s3, s4, s5, s6, s7, s8, s9);
for s_name_type use
(S0 => 0, S1 => 1, S2 => 2, S3 => 3, S4 => 4,
S5 => 5, S6 => 6, S7 => 7, S8 => 8, S9 => 9);

subtype n_t is Positive range 3..Positive'Last;

package s_names_p is new Ada.Containers.Vectors

(Index_Type => n_t, Element_Type => s_name_type);
k : integer := 7;

n : constant integer := 7;

-- n : constant integer := k; -- uncomment this line and comment out the line above.

s_names: constant s_names_p.Vector := [for i in 3..n => S0];
begin
Ada.Text_IO.Put_Line(s_names'Image);
end test1a;

reinert

[reinert]

Sorry for some typos in my latest post, but the intelligent reader should understand :-)

reinert