c++ - CFRelease 导致崩溃

Question

以下代码导致我的 C++ 应用程序崩溃:

CFMutableDictionaryRef property_dictionary = CFDictionaryCreateMutable( kCFAllocatorDefault, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks );

if ( ! property_dictionary )
  break;

CFDictionarySetValue( property_dictionary, CFSTR( "somekey" ), CFSTR("someval") );
CFMutableDictionaryRef match_dictionary = CFDictionaryCreateMutable( kCFAllocatorDefault, 0,
                    &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks );

if ( ! match_dictionary )
  break;

CFDictionarySetValue( match_dictionary, CFSTR(kIOPropertyMatchKey), property_dictionary );

io_iterator_t service = IOServiceGetMatchingService( kIOMasterPortDefault, match_dictionary );

if ( property_dictionary != NULL )
  CFRelease( property_dictionary );

// the following bit causes crash
if ( match_dictionary != NULL )
  CFRelease( match_dictionary );

不知IOServiceGetMatchingService是否与此有关。

Answer 1

IOServiceGetMatchingService() 在内存管理方面很特殊。它使用对传入字典的一个引用。由于您的代码只有一个引用，它在调用后不再拥有 match_dictionary 字典，并且不得对其调用 CFRelease()。

来自docs :

matching A CF dictionary containing matching information, of which one reference is always consumed by this function…