Re: [PATCH] PR ada/66205 gnatbind generates invalid code when finalization is enabled in restricted runtime

[Simon Wright <simon@pushface.org>]

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On 7 Mar 2017, at 16:20, Simon Wright <simon@pushface.org> wrote:
> 
> On 19 Dec 2015, at 22:05, Simon Wright <simon@pushface.org> wrote:
>> 
>> On 12 Nov 2015, at 10:02, Arnaud Charlet <charlet@adacore.com> wrote:
>>> 
>>>>> This situation arises, for example, with an embedded RTS that
>>>>> incorporates the
>>>>> Ada 2012 generalized container iterators.
>>>> 
>>>> I should add, this PR is the ???other half??? of PR ada/66242, which is fixed
>>>> in GCC 6; so please can it be reviewed?
>>> 
>>> The proper patch for PR ada/66242 hasn't been committed yet (it's pending),
>>> so I'd rather review the situation once PR ada/66242 is dealt with.
>>> 
>>> I'm not convinced at all that your patch is the way to go, so I'd rather
>>> consider it only after PR ada/66242 is solved properly.
>> 
>> Looks as though PR ada/66242 has been sorted out.
>> 
>> Since we can now *compile* code that is built with finalization enabled in a restricted runtime, but we can't *bind* it, could we take another look at this? the patch I provided in this thread still applies at snapshot 20151213 with minor offsets (8).
> 
> Same problem exists in gcc version 7.0.1 20170302 (experimental) (GCC).

and with gcc 8.0.0 20171102 (experimental) (r254339); and there's been no change to the affected file (bindgen.adb) since then.

I've come up with a considerably simpler patch, which merely causes the procedure adafinal to be generated with a null body if the restriction No_Task_Termination is set (note, this restriction is part of the Ravenscar profile; if tasks can't terminate, program level finalization can't happen [ARM 10.2(25), "When the environment task completes (normally or abnormally), it waits for the termination of all such tasks, and then finalizes any remaining objects of the partition."]

I've bootstrapped the compiler (x86_64-apple-darwin15), and "make check-ada" produces the same results with and without the patch (the same 3 FAILs occur in both, in gnat.sum). For the arm-eabi compiler, I successfully make and run builds for an STM32F4 target without exception propagation but with and without finalization.

gcc/ada/Changelog:

2017-12-05  Simon Wright <simon@pushface.org>

     PR ada/66205
      * bindgen.adb (Gen_AdaFinal): If the restriction
         No_Task_Termination is present, generate a null body.


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diff --git a/gcc/ada/bindgen.adb b/gcc/ada/bindgen.adb
index e3d875bc8cc..b02360087ef 100644
--- a/gcc/ada/bindgen.adb
+++ b/gcc/ada/bindgen.adb
@@ -450,6 +450,20 @@ package body Bindgen is
    begin
       WBI ("   procedure " & Ada_Final_Name.all & " is");
 
+      --  If task termination isn't allowed (as is the case in
+      --  restricted runtimes, such as Ravenscar or ZFP, but may not
+      --  be the case for all configurable runtimes), we don't need
+      --  program-level finalization.
+
+      if Cumulative_Restrictions.Set (No_Task_Termination) then
+         --  Nothing to do
+         WBI ("   begin");
+         WBI ("      null;");
+         WBI ("   end " & Ada_Final_Name.all & ";");
+         WBI ("");
+         return;
+      end if;
+
       --  Call s_stalib_adafinal to await termination of tasks and so on. We
       --  want to do this if there is a main program, either in Ada or in some
       --  other language. (Note that Bind_Main_Program is True for Ada mains,