swig生成的扩展发生内存泄漏

我有一个内存泄漏问题,用PHIG在PHP中包装C++库。当包含复杂类型的C++的回调被发送到PHP,而启用了导演时,似乎会发生这种情况。下面是一个独立的例子来重现泄漏:

Client.hpp:

#ifndef CLIENT_HPP_
#define CLIENT_HPP_

#include <vector>
#include "ProcedureCallback.hpp"

class Client {
public:
    void invoke(ProcedureCallback *callback) {
        callback->callback(std::vector<int>(0));
    }
};

#endif /* CLIENT_HPP_ */

程序确认.hpp:

#ifndef PROCEDURECALLBACK_HPP_
#define PROCEDURECALLBACK_HPP_

#include <vector>

class ProcedureCallback {
public:
    virtual void callback(std::vector<int>) = 0;
};

#endif /* PROCEDURECALLBACK_HPP_ */

所以要使用它,您可以创建一个 Client ,传递子类 ProcedureCallback 对客户的 invoke 方法,然后客户端调用 callback 方法,并传递一个空的int向量。

这是swig接口文件:

%module(directors="1") debugasync
%feature("director");

%{
#include "Client.hpp"
#include "ProcedureCallback.hpp"
%}

%include "Client.hpp"
%include "ProcedureCallback.hpp"

它的输出非常大,所以我把它放在Pastebin上: debugasync_wrap.cpp . 对此文件感兴趣的可能是swigdirector_procedureCallback::callback(第1319行):

void SwigDirector_ProcedureCallback::callback(std::vector< int > arg0) {
  zval *args[1];
  zval *result, funcname;
  MAKE_STD_ZVAL(result);
  ZVAL_STRING(&funcname, (char *)"callback", 0);
  if (!swig_self) {
    SWIG_PHP_Error(E_ERROR, "this pointer is NULL");
  }

  zval obj0;
  args[0] = &obj0;
  {
    SWIG_SetPointerZval(&obj0, SWIG_as_voidptr(&arg0), SWIGTYPE_p_std__vectorT_int_t, 2);
  }
  call_user_function(EG(function_table), (zval**)&swig_self, &funcname,
    result, 1, args TSRMLS_CC);
  FREE_ZVAL(result);
  return;
fail:
  zend_error(SWIG_ErrorCode(),"%s",SWIG_ErrorMsg());
}

这可能也很有趣(第827行):

static void
SWIG_ZTS_SetPointerZval(zval *z, void *ptr, swig_type_info *type, int newobject TSRMLS_DC) {
  swig_object_wrapper *value=NULL;
  /*
   * First test for Null pointers.  Return those as PHP native NULL
   */
  if (!ptr ) {
    ZVAL_NULL(z);
    return;
  }
  if (type->clientdata) {
    if (! (*(int *)(type->clientdata)))
      zend_error(E_ERROR, "Type: %s failed to register with zend",type->name);
    value=(swig_object_wrapper *)emalloc(sizeof(swig_object_wrapper));
    value->ptr=ptr;
    value->newobject=newobject;
    if (newobject <= 1) {
      /* Just register the pointer as a resource. */
      ZEND_REGISTER_RESOURCE(z, value, *(int *)(type->clientdata));
    } else {
      /*
       * Wrap the resource in an object, the resource will be accessible
       * via the "_cPtr" member. This is currently only used by
       * directorin typemaps.
       */
      value->newobject = 0;
      zval *resource;
      MAKE_STD_ZVAL(resource);
      ZEND_REGISTER_RESOURCE(resource, value, *(int *)(type->clientdata));
      zend_class_entry **ce = NULL;
      zval *classname;
      MAKE_STD_ZVAL(classname);
      /* _p_Foo -> Foo */
      ZVAL_STRING(classname, (char*)type->name+3, 1);
      /* class names are stored in lowercase */
      php_strtolower(Z_STRVAL_PP(&classname), Z_STRLEN_PP(&classname));
      if (zend_lookup_class(Z_STRVAL_P(classname), Z_STRLEN_P(classname), &ce TSRMLS_CC) != SUCCESS) {
        /* class does not exist */
        object_init(z);
      } else {
        object_init_ex(z, *ce);
      }
      Z_SET_REFCOUNT_P(z, 1);
      Z_SET_ISREF_P(z);
      zend_hash_update(HASH_OF(z), (char*)"_cPtr", sizeof("_cPtr"), (void*)&resource, sizeof(zval), NULL);
      FREE_ZVAL(classname);
    }
    return;
  }
  zend_error(E_ERROR, "Type: %s not registered with zend",type->name);
}

并演示PHP中的内存泄漏( debugasync.php 是由swig生成的一组代理类,我也将其上载到了pastebin):

<?php

require('debugasync.php');

class MyCallback extends ProcedureCallback {
    public function callback($intVector) {}
}

$client = new Client();
$callback = new MyCallback();

while (true) {
    print(number_format(memory_get_usage()) . "\n");
    for ($j = 0; $j < 1000; $j++) {
        $client->invoke($callback);
    }
}

这将打印内存使用情况,执行1K调用并重复。运行它会显示快速增长的内存空间:

$ php test.php 
692,664
1,605,488
2,583,232
3,634,776
4,538,784
5,737,760
6,641,768
7,545,816
^C

还需要注意的是,如果C++回调传递一个基元(即 int )而不是复杂类型(即 std::vector<int> )没有内存泄漏。

内存泄漏的原因是什么?

更一般地说,我可以使用什么工具来解决这个问题?Valgrind的Massif甚至在用调试符号构建了PHP之后,也没有真正缩小范围。