Re: Alternative for Gnat Studio

[Simon Wright <simon@pushface.org>]

ldries46 <bertus.dries@planet.nl> writes:

> My problem has become more acute. Till now I avoided the debugging
> option in the GNAT 2020 Community edition by badding print statements 
> within the normal running program but now I have an error mentioned
> somewhere within the Ada. Unbounded_Strings which is used on a lot of 
> positions in the program. The only way I know to detect wher the
> problem is is using the debug option with several brakpoints and as
> possible shifting these around to find this error but uding the debu
> option just makes the program coming to the "program does not
> react".

If you can possibly bear it, you should try the command line. I don't
know what that would look like on Windows (unless you're using Cygwin?
which is Unix-y).

Sample program:

   pragma Assertion_Policy (Check);
   procedure Raiser is
      procedure Inner (N : Natural) is
         pragma Assert (N > 5);
      begin
         Inner (N - 1);
      end Inner;
   begin
      Inner (10);
   end Raiser;

Now, I'm sure you've built with a proper GPR, but to simplify the
example:

   gnatmake -g -O raiser.adb

Here, this produces the executable "raiser" in the current directory,
but if your GPR specifies the Object_Dir and not the Exec_Dir the
executable (in your case "raiser.exe") ends up in the Object_Dir, drat
it.

A very simple debugging session, assuming that the command "gdb" runs OK
might look like:

   $ gdb raiser
   GNU gdb (GDB) 7.10 for GNAT Community 2020 [rev=52ea9f0a422c99f69e7e6c44a04e654ceebc42e3]
   Copyright (C) 2015 Free Software Foundation, Inc.
   License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
   This is free software: you are free to change and redistribute it.
   See your support agreement for details of warranty and support.
   If you do not have a current support agreement, then there is absolutely
   no warranty for this version of GDB.  Type "show copying"
   and "show warranty" for details.
   This GDB was configured as "x86_64-apple-darwin17.7.0".
   Type "show configuration" for configuration details.For help, type "help".
   Type "apropos word" to search for commands related to "word"...
   Reading symbols from raiser...done.

Stop on any exception

   (gdb) catch exception
   Catchpoint 1: all Ada exceptions

Run to the start of the program

   (gdb) start
   Temporary breakpoint 2 at 0x100001f54: file raiser.adb, line 9.
   Starting program: /Users/simon/tmp/raiser 
   [New Thread 0x2303 of process 71543]
   
   Temporary breakpoint 2, raiser () at raiser.adb:9
   9	   Inner (10);

Carry on

   (gdb) continue
   Continuing.

Oops! (note, gdb knows to stop at the point in my code where the
exception was raised, rather than down in the details of the runtime
system calls)

   Catchpoint 1, SYSTEM.ASSERTIONS.ASSERT_FAILURE (raiser.adb:4) at 0x0000000100001f17 in raiser.inner (n=5) at raiser.adb:4
   4	      pragma Assert (N > 5);

Print a backtrace of how we got here

   (gdb) backtrace
   #0  <__gnat_debug_raise_exception> (
       e=0x1000142e0 <system.assertions.assert_failure>, message=...)
       at s-excdeb.adb:43
   #1  0x00000001000038ed in ada.exceptions.complete_occurrence (x=0x1004040c0)
       at a-except.adb:931
   #2  0x00000001000038fd in ada.exceptions.complete_and_propagate_occurrence (
       x=0x1004040c0) at a-except.adb:942
   #3  0x0000000100003952 in <__gnat_raise_exception> (
       e=0x1000142e0 <system.assertions.assert_failure>, message=...)
       at a-except.adb:984
   #4  0x0000000100004c13 in system.assertions.raise_assert_failure (msg=...)
       at s-assert.adb:46
   #5  0x0000000100001f17 in raiser.inner (n=5) at raiser.adb:4
   #6  0x0000000100001f3c in raiser.inner (n=6) at raiser.adb:6
   #7  0x0000000100001f3c in raiser.inner (n=7) at raiser.adb:6
   #8  0x0000000100001f3c in raiser.inner (n=8) at raiser.adb:6
   #9  0x0000000100001f3c in raiser.inner (n=9) at raiser.adb:6
   #10 0x0000000100001f3c in raiser.inner (n=10) at raiser.adb:6
   #11 0x0000000100001f65 in raiser () at raiser.adb:9

Look at the code at frame 8 (#8 in the backtrace)

   (gdb) frame 8
   #8  0x0000000100001f3c in raiser.inner (n=8) at raiser.adb:6
   6	      Inner (N - 1);

Print a variable

   (gdb) print n
   $1 = 8
   (gdb)