Recursion broken recently by -OoDeadValues in mainline FPC (3.3.1)
lazarus / 21-General

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Bogen85 · 2022-11-08 08:38

I'll likely file an issue on this soon.

Recursion with -OoDeadValues was working a week or so ago in mainline
git, have not determined when it broke.

Given the following program:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
recurse; procedure pr1(const i, final: integer);  var i0: integer;  
procedure pr2(const i1: integer);    begin      if i0 > final then
exit;      if i1 > final then exit;      writeln(i0, ' ', i1);     
inc(i0);      pr2(i1+1);    end;  begin    i0 := i;    pr2(i); 
end; begin  pr1(1, 5);end. 
Compiled and ran with FPC stable, it runs correctly:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i $ fpc \   
   -gl -gw3 -Xi -Sm -Sg -Os -Mobjfpc -Sh \        -MadvancedRecords \ 
      -McVar -MhintDirective \        -OoPeepHole -OoTailRec
-OoRemoveEmptyProcs -OoConstProp \        -OoDFA -OoCSE -OoDeadStore
-OoDeadValues \        -vnewh -Sewh ./recurse.pas && mv recurse
recurse-stable && ./recurse-stableHint: Start of reading config file
/etc/fpc.cfgHint: End of reading config file /etc/fpc.cfgFree Pascal
Compiler version 3.2.2 [2022/08/31] for x86_64Copyright (c) 1993-2021
by Florian Klaempfl and othersTarget OS: Linux for x86-64Compiling
./recurse.pasLinking recurse21 lines compiled, 0.1 sec2 hint(s)
issued1 12 23 34 45 5 
Compiled and ran with FPC mainline as follow, it fails:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i $ fpc -gl
-gw3 -Xi -Sm -Sg -Os -Mobjfpc -Sh \        -MfunctionReferences
-ManonymousFunctions -MadvancedRecords \        -McVar
-MimplicitFunctionSpecialization -MhintDirective \        -OoPeepHole
-OoTailRec -OoRemoveEmptyProcs -OoConstProp \        -vnewh -Sewh \  
    -OoDFA -OoCSE -OoUnusedPara -OoDeadStore \        -OoDeadValues \ 
      ./recurse.pas && mv recurse recurse-current && ./recurse-
currentHint: Start of reading config file
/home/dev/fpc_usr/lib/fpc/etc/fpc.cfgHint: End of reading config file
/home/dev/fpc_usr/lib/fpc/etc/fpc.cfgFree Pascal Compiler version
3.3.1 [2022/11/07] for x86_64Copyright (c) 1993-2022 by Florian
Klaempfl and othersTarget OS: Linux for x86-64Compiling
./recurse.pasLinking recurse21 lines compiled, 0.2 sec, 156832 bytes
code, 1139976 bytes data2 hint(s) issued1 12 13 14 15 1 
Remove the -OoDeadValues and it succeeds:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i $  fpc -gl
-gw3 -Xi -Sm -Sg -Os -Mobjfpc -Sh \        -MfunctionReferences
-ManonymousFunctions -MadvancedRecords \        -McVar
-MimplicitFunctionSpecialization -MhintDirective \        -OoPeepHole
-OoTailRec -OoRemoveEmptyProcs -OoConstProp \        -vnewh -Sewh \  
    -OoDFA -OoCSE -OoUnusedPara  -OoDeadStore \        ./recurse.pas
&& mv recurse recurse-current && ./recurse-currentHint: Start of
reading config file /home/dev/fpc_usr/lib/fpc/etc/fpc.cfgHint: End of
reading config file /home/dev/fpc_usr/lib/fpc/etc/fpc.cfgFree Pascal
Compiler version 3.3.1 [2022/11/07] for x86_64Copyright (c) 1993-2022
by Florian Klaempfl and othersTarget OS: Linux for x86-64Compiling
./recurse.pasLinking recurse21 lines compiled, 0.2 sec, 156848 bytes
code, 1139976 bytes data2 hint(s) issued1 12 23 34 45 5 
Mainline used:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i $ git
describe3.3.1-12089-ga2789d611f

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Bogen85 · 2022-11-08 08:41

I know that Code: Pascal  [Select][+][-]window.onload = function(){var
x1 = document.getElementById("main_content_section"); if (x1) { var x
= document.getElementsByClassName("geshi");for (var i = 0; i if i1 >
final then exit; is redundant.

What I consider failing is i1 not incrementing.

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Bogen85 · 2022-11-08 14:58

This highlights the issue more explicitly, both counters should track,
and termination should be based on i1, not i0

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
recurse; procedure pr1(const i, final: integer);  var i0: integer;  
procedure pr2(const i1: integer);    begin      if i1 > final then
exit;      if i0 > (final*2) then exit;      writeln(i0, ' ', i1);   
 inc(i0);      pr2(i1+1);    end;  begin    i0 := i;    pr2(i); 
end; begin  pr1(1, 5);end. 
Broken output:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i 1 12 13 14
15 16 17 18 19 110 1 
Correct output:
Code: Text  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i 1 12 23 34
45 5

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Bogen85 · 2022-11-11 08:28

https://gitlab.com/freepascal.org/fpc/source/-/issues/39988