[5.4] Use do while instead of goto

[bepsvpt]

No description provided.

[GrahamCampbell]

Goto was used because it keeps the call stack down. Your implementation will crash after too many retrys.

[bepsvpt]

I'm using the following code to get the stack trace, it seems there is no different between do while and goto. Is there something wrong with the following code?

do while: https://ideone.com/MYBV9w
goto: https://ideone.com/EoGhdF

[taylorotwell]

Here is the reasoning for using goto given in the library that inspired the function: igorw/retry#3

[bepsvpt]

Here is the opcodes generated using php70, I remove $sleep parameter and optimize goto version to make comparison easier.

do_while.php

<?php

function retry($times, callable $callback)
{
    do {
        try {
            return $callback();
        } catch (Exception $e) {
        }
    } while (--$times);

    throw $e;
}

do_while.php opcodes

filename:       do_while.php
function name:  retry
number of ops:  19
compiled vars:  !0 = $times, !1 = $callback, !2 = $e
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   3     0  E >   EXT_NOP
         1        RECV                                             !0
         2        RECV                                             !1
   5     3        NOP
   6     4    >   NOP
   7     5        EXT_STMT
         6        INIT_DYNAMIC_CALL                                        !1
         7        EXT_FCALL_BEGIN
         8        DO_FCALL                                      0  $3
         9        EXT_FCALL_END
        10      > RETURN                                                   $3
        11*       JMP                                                      ->13
   8    12  E > > CATCH                                                    'Exception', !2
  10    13    >   PRE_DEC                                          $4      !0
        14      > JMPNZ                                                    $4, ->4
  12    15    >   EXT_STMT
        16      > THROW                                         0          !2
  13    17*       EXT_STMT
        18*     > RETURN                                                   null

goto.php

<?php

function retry($times, callable $callback)
{
    beginning:
    try {
        return $callback();
    } catch (Exception $e) {
        if (! --$times) {
            throw $e;
        }

        goto beginning;
    }
}

goto.php opcodes

filename:       goto.php
function name:  retry
number of ops:  22
compiled vars:  !0 = $times, !1 = $callback, !2 = $e
line     #* E I O op                           fetch          ext  return  operands
-------------------------------------------------------------------------------------
   3     0  E >   EXT_NOP
         1        RECV                                             !0
         2        RECV                                             !1
   6     3    >   NOP
   7     4        EXT_STMT
         5        INIT_DYNAMIC_CALL                                        !1
         6        EXT_FCALL_BEGIN
         7        DO_FCALL                                      0  $3
         8        EXT_FCALL_END
         9      > RETURN                                                   $3
        10*       JMP                                                      ->20
   8    11  E > > CATCH                                                    'Exception', !2
   9    12    >   EXT_STMT
        13        PRE_DEC                                          $4      !0
        14        BOOL_NOT                                         ~5      $4
        15      > JMPZ                                                     ~5, ->18
  10    16    >   EXT_STMT
        17      > THROW                                         0          !2
  13    18    >   EXT_STMT
        19      > JMP                                                      ->3
  15    20*       EXT_STMT
        21*     > RETURN                                                   null

@taylorotwell, it seems that goto version takes additional BOOL_NOT(#14) and JMP(#19) opcodes.