Valgrind 在基本 Qt 應用程序上：報告大量泄漏

Question

所以我想看看在通過 Valgrind 運行時，從簡單的 Makefile 編譯的基本 Qt4 應用程序會發生什么。 什么會導致這些泄漏？ 我正在刪除任何動態分配的對象。 此外，在退出程序時，我只單擊右上角的關閉 (X)。 GUI庫是否只是不是“free()”的任何 memory 他們malloc()'d ？

從 qmake 命令減少的 Makefile 是：

####### Compiler, tools and options

CXX           = g++
CXXFLAGS      = -pipe -O2 -Wall -W
LIBS_INCLUDE  = ${HOME}
INCPATH       = -I$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/mkspecs/default \
                -I. \
                -I$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/include/QtCore \
                -I$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/include/QtGui \
                -I$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/include 
LINK          = g++
LFLAGS        = -Wl,-O1 -Wl,-rpath,$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/lib
LIBS          = $(SUBLIBS)  -L$(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/lib -lQtGui -lQtCore -lpthread
QMAKE         = $(LIBS_INCLUDE)/QtSDK/Desktop/Qt/473/gcc/bin/qmake
OBJECTS_DIR   = ./
SOURCES       = main.cpp
OBJECTS       = main.o
QMAKE_TARGET  = Main
TARGET        = Main

####### Build rules
first: all

all: $(TARGET)

$(TARGET):  $(OBJECTS)
        $(LINK) $(LFLAGS) -o $(TARGET) $(OBJECTS) $(OBJCOMP) $(LIBS)

####### Compile

main.o: main.cpp
        $(CXX) -c $(CXXFLAGS) $(INCPATH) -o main.o main.cpp

唯一的源代碼是：

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget window;
    window.resize( 320,240 );
    window.setWindowTitle( 
        QApplication::translate( "toplevel", "Top-level Widget" ) );
    window.show( );

    QPushButton *button = new QPushButton(
        QApplication::translate( "childwidget", "Press me"), &window );
    button->move( 100, 100 );
    button->show( );
    delete button;
    return app.exec();
}

通過 valgrind 運行時，我得到以下信息（刪除了中間的大部分）：

==3836== Memcheck, a memory error detector
==3836== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==3836== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==3836== Command: ./Main
==3836== 
Xlib:  extension "RANDR" missing on display ":0.0".
==3836== 
==3836== HEAP SUMMARY:
==3836==     in use at exit: 924,383 bytes in 8,679 blocks
==3836==   total heap usage: 37,234 allocs, 28,555 frees, 4,314,180 bytes allocated
==3836== 
==3836== 1 bytes in 1 blocks are possibly lost in loss record 1 of 4,534
==3836==    at 0x400677E: malloc (vg_replace_malloc.c:195)
==3836==    by 0xA1DFA4: g_malloc (in /lib/libglib-2.0.so.0.2600.0)
==3836==    by 0xA37F29: g_strdup (in /lib/libglib-2.0.so.0.2600.0)
==3836==    by 0xB2A6FA: g_param_spec_string (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0x41F36473: ??? (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836==    by 0xB3D237: g_type_class_ref (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB20B38: g_object_newv (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB212EF: g_object_new (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0x41F34857: gtk_settings_get_for_screen (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836==    by 0x41ED0CB6: ??? (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836==    by 0xB377C7: g_cclosure_marshal_VOID__OBJECT (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB1ABE2: g_closure_invoke (in /lib/libgobject-2.0.so.0.2600.0)
==3836== 
...
==3836== 
==3836== 23,048 bytes in 1 blocks are possibly lost in loss record 4,531 of 4,534
==3836==    at 0x400677E: malloc (vg_replace_malloc.c:195)
==3836==    by 0x16F42D: ??? (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x17400B: ft_mem_qalloc (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x174063: ft_mem_alloc (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x174508: ft_mem_qrealloc (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x17457F: ft_mem_realloc (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x1A2E52: ??? (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x1A709B: ??? (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x180338: ??? (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x175B5D: ??? (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x1780B0: FT_Open_Face (in /usr/lib/libfreetype.so.6.6.0)
==3836==    by 0x1791FF: FT_New_Face (in /usr/lib/libfreetype.so.6.6.0)
==3836== 
==3836== 53,244 bytes in 29 blocks are possibly lost in loss record 4,534 of 4,534
==3836==    at 0x400677E: malloc (vg_replace_malloc.c:195)
==3836==    by 0xA1DFA4: g_malloc (in /lib/libglib-2.0.so.0.2600.0)
==3836==    by 0xA36050: g_slice_alloc (in /lib/libglib-2.0.so.0.2600.0)
==3836==    by 0xA36315: g_slice_alloc0 (in /lib/libglib-2.0.so.0.2600.0)
==3836==    by 0xB40077: g_type_create_instance (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB1CE35: ??? (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB205C6: g_object_newv (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0xB212EF: g_object_new (in /lib/libgobject-2.0.so.0.2600.0)
==3836==    by 0x54B8FA3: ??? (in /usr/lib/gtk-2.0/2.10.0/engines/libclearlooks.so)
==3836==    by 0x41F0CDDD: ??? (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836==    by 0x41F11C24: gtk_rc_get_style (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836==    by 0x4200A81F: ??? (in /usr/lib/libgtk-x11-2.0.so.0.2200.0)
==3836== 
==3836== LEAK SUMMARY:
==3836==    definitely lost: 1,912 bytes in 7 blocks
==3836==    indirectly lost: 5,060 bytes in 250 blocks
==3836==      possibly lost: 491,358 bytes in 2,893 blocks
==3836==    still reachable: 426,053 bytes in 5,529 blocks
==3836==         suppressed: 0 bytes in 0 blocks
==3836== Reachable blocks (those to which a pointer was found) are not shown.
==3836== To see them, rerun with: --leak-check=full --show-reachable=yes
==3836== 
==3836== For counts of detected and suppressed errors, rerun with: -v
==3836== ERROR SUMMARY: 1336 errors from 1336 contexts (suppressed: 114 from 11)

Answer 1

我編譯了您的簡短應用程序並且（使用 Visual Studio crt 內存泄漏檢測器）找不到任何 memory 泄漏。 所以無論 valgrind 報告什么都與你的代碼沒有直接關系。

但是，您要在應用程序實際運行之前刪除 QPushButton。 通常 QWindows 的所有權轉移給父 window，因此您不需要自己清理對象，父 window 會為您處理（如果不是這種情況，文檔中會說明）。

因此，要更正您的代碼，只需刪除刪除即可。