[Swig-user] PHP callback with arguments via SWIG generates uninitialised values in valgrind

[john paul]

I'm trying to understand why valgrind complains about 'Conditional jump or move depends on uninitialised value(s)' in the code below. I took the callback example in swig 2.0.4 and added an argument to the callback.

Can anyone help me understand why this is happening?
 

In example.h

 
 
/* File : example.h */ 

#include <iostream> 

class Callback { 
  public: 
    virtual ~Callback() { std::cout << "Callback::~Callback()" << std:: endl; } 
    virtual void run(const std::string &s) { std::cout << s << std::endl; } 
}; 


class Caller { 
  private: 
    Callback *_callback; 
  public: 
    Caller(): _callback(0) {} 
   ~Caller() { delCallback(); } 
   void delCallback() { delete _callback; _callback = 0; } 
   void setCallback(Callback *cb) { delCallback(); _callback = cb; } 
   void call(const std::string &s) { if (_callback) _callback->run(s); } 
}; 

In example.i

 
 
/* File : example.i */ 
%module(directors="1") example 
%{ 
#include "example.h" 
%} 

%include "std_string.i" 

/* turn on director wrapping Callback */ 
%feature("director") Callback; 

%include "example.h" 

In runme.php

 
 
# This file illustrates the cross language polymorphism using directors. 

require("example.php"); 

# Class, which overwrites Callback::run(). 

class PhpCallback extends Callback { 
  function run($msg) { 
    //print "PhpCallback.run()\n"; 
    print "PhpCallback ".$msg.PHP_EOL; 
  } 
}; 

# Create an Caller instance 

$caller = new Caller(); 



print "\n"; 
print "Adding and calling a PHP callback\n"; 
print "------------------------------------\n"; 

# Add a PHP callback. 

$callback = new PhpCallback(); 
$callback->thisown = 0; 
$caller->setCallback($callback); 
$caller->call("hello"); 
$caller->delCallback(); 

# All done. 

print "php exit\n"; 

Output

 
 
$php runme.php 

Adding and calling a PHP callback 
------------------------------------ 
PhpCallback hello 
Callback::~Callback() 
php exit 

Valgrind output

 
 
$valgrind --leak-check=full --track-origins=yes php runme.php 
==6660== Memcheck, a memory error detector 
==6660== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al. 
==6660== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info 
==6660== Command: php runme.php 
==6660== 

Adding and calling a PHP callback 
------------------------------------ 
PhpCallback hello 
==6660== Conditional jump or move depends on uninitialised value(s) 
==6660==    at 0x5F93AF: _zval_ptr_dtor (in /usr/bin/php) 
==6660==    by 0x631D4D: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x5FB09B: zend_call_function (in /usr/bin/php) 
==6660==    by 0x5FB40F: call_user_function_ex (in /usr/bin/php) 
==6660==    by 0x5FB461: call_user_function (in /usr/bin/php) 
==6660==    by 0xA7D0D25: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1353) 
==6660==    by 0xA7D20D7: Caller::call(std::string const&) (in /home/xvf/downloads/swig-2.0.4/Examples/php/callback/example.so) 
==6660==    by 0xA7D17E4: _wrap_Caller_call (example_wrap.cxx:1563) 
==6660==    by 0x68CE4C: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x6090A8: zend_execute_scripts (in /usr/bin/php) 
==6660==  Uninitialised value was created by a stack allocation 
==6660==    at 0xA7D0BF2: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1338) 
==6660== 
==6660== Conditional jump or move depends on uninitialised value(s) 
==6660==    at 0x5F93F5: _zval_ptr_dtor (in /usr/bin/php) 
==6660==    by 0x631D4D: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x5FB09B: zend_call_function (in /usr/bin/php) 
==6660==    by 0x5FB40F: call_user_function_ex (in /usr/bin/php) 
==6660==    by 0x5FB461: call_user_function (in /usr/bin/php) 
==6660==    by 0xA7D0D25: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1353) 
==6660==    by 0xA7D20D7: Caller::call(std::string const&) (in /home/xvf/downloads/swig-2.0.4/Examples/php/callback/example.so) 
==6660==    by 0xA7D17E4: _wrap_Caller_call (example_wrap.cxx:1563) 
==6660==    by 0x68CE4C: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x6090A8: zend_execute_scripts (in /usr/bin/php) 
==6660==  Uninitialised value was created by a stack allocation 
==6660==    at 0xA7D0BF2: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1338) 
==6660== 
==6660== Conditional jump or move depends on uninitialised value(s) 
==6660==    at 0x5F93AF: _zval_ptr_dtor (in /usr/bin/php) 
==6660==    by 0x5FAF2D: zend_call_function (in /usr/bin/php) 
==6660==    by 0x5FB40F: call_user_function_ex (in /usr/bin/php) 
==6660==    by 0x5FB461: call_user_function (in /usr/bin/php) 
==6660==    by 0xA7D0D25: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1353) 
==6660==    by 0xA7D20D7: Caller::call(std::string const&) (in /home/xvf/downloads/swig-2.0.4/Examples/php/callback/example.so) 
==6660==    by 0xA7D17E4: _wrap_Caller_call (example_wrap.cxx:1563) 
==6660==    by 0x68CE4C: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x6090A8: zend_execute_scripts (in /usr/bin/php) 
==6660==    by 0x5B5F52: php_execute_script (in /usr/bin/php) 
==6660==    by 0x42644D: ??? (in /usr/bin/php) 
==6660==  Uninitialised value was created by a stack allocation 
==6660==    at 0xA7D0BF2: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1338) 
==6660== 
==6660== Conditional jump or move depends on uninitialised value(s) 
==6660==    at 0x5F93F5: _zval_ptr_dtor (in /usr/bin/php) 
==6660==    by 0x5FAF2D: zend_call_function (in /usr/bin/php) 
==6660==    by 0x5FB40F: call_user_function_ex (in /usr/bin/php) 
==6660==    by 0x5FB461: call_user_function (in /usr/bin/php) 
==6660==    by 0xA7D0D25: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1353) 
==6660==    by 0xA7D20D7: Caller::call(std::string const&) (in /home/xvf/downloads/swig-2.0.4/Examples/php/callback/example.so) 
==6660==    by 0xA7D17E4: _wrap_Caller_call (example_wrap.cxx:1563) 
==6660==    by 0x68CE4C: ??? (in /usr/bin/php) 
==6660==    by 0x62D59A: execute (in /usr/bin/php) 
==6660==    by 0x6090A8: zend_execute_scripts (in /usr/bin/php) 
==6660==    by 0x5B5F52: php_execute_script (in /usr/bin/php) 
==6660==    by 0x42644D: ??? (in /usr/bin/php) 
==6660==  Uninitialised value was created by a stack allocation 
==6660==    at 0xA7D0BF2: SwigDirector_Callback::run(std::string const&) (example_wrap.cxx:1338) 
==6660== 
Callback::~Callback() 
php exit 
==6660== 
==6660== HEAP SUMMARY: 
==6660==     in use at exit: 15,624 bytes in 27 blocks 
==6660==   total heap usage: 21,103 allocs, 21,076 frees, 3,672,898 bytes allocated 
==6660== 
==6660== 88 (32 direct, 56 indirect) bytes in 1 blocks are definitely lost in loss record 5 of 12 
==6660==    at 0x4C2993D: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==6660==    by 0x783B2C3: ??? 
==6660==    by 0x78A804E: ??? 
==6660==    by 0x75BDA99: ??? 
==6660==    by 0x75BF988: ??? 
==6660==    by 0x75C51B4: ??? 
==6660==    by 0x6F17E72: ??? 
==6660==    by 0x6F1F868: ??? 
==6660==    by 0x6CE8127: ??? 
==6660==    by 0x6096AE: zend_startup_module_ex (in /usr/bin/php) 
==6660==    by 0x615303: zend_hash_apply (in /usr/bin/php) 
==6660==    by 0x60CF29: zend_startup_modules (in /usr/bin/php) 
==6660== 
==6660== LEAK SUMMARY: 
==6660==    definitely lost: 32 bytes in 1 blocks 
==6660==    indirectly lost: 56 bytes in 2 blocks 
==6660==      possibly lost: 0 bytes in 0 blocks 
==6660==    still reachable: 15,536 bytes in 24 blocks 
==6660==         suppressed: 0 bytes in 0 blocks 
==6660== Reachable blocks (those to which a pointer was found) are not shown. 
==6660== To see them, rerun with: --leak-check=full --show-reachable=yes 
==6660== 
==6660== For counts of detected and suppressed errors, rerun with: -v 
==6660== ERROR SUMMARY: 5 errors from 5 contexts (suppressed: 2 from 2)