debug模式下体积过大的话，选择release编译会缩小很大一部分体积。
选择创建qt库项目，根据提示选择相应配置：
Type：Shared Libray；Statically linked Library；QT Plugin
Class name:dlllibtest
QT module:None;Core;Gui;Widgets（对于一般函数不引用qt库的话封装经测试选择None和Core一样的效果包括生成的dll大小等）
Head file:默认为类名.h（可改）
Sorce file：默认为类名.cpp(可改）
配置好后会自动生成3个文件，可以按如下所示编写dll代码
1.pro文件
QT -= gui
TEMPLATE = lib
DEFINES += DLLLIBTEST_LIBRARY
CONFIG += c++11
# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS
# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0
SOURCES += \
dlllibtest.cpp
HEADERS += \
DllLibTest_global.h \
dlllibtest.h
# Default rules for deployment.
unix {
target.path = /usr/lib
}
!isEmpty(target.path): INSTALLS += target
2._global.h文件（将此文件里的声名复制到实现的头文件中，QT module:None;Core两种模式下内容有些差别但复制方式类似）
#ifndef DLLLIBTEST_GLOBAL_H
#define DLLLIBTEST_GLOBAL_H
#include <QtCore/qglobal.h>
#if defined(DLLLIBTEST_LIBRARY)
# define DLLLIBTEST_EXPORT Q_DECL_EXPORT
#else
# define DLLLIBTEST_EXPORT Q_DECL_IMPORT
#endif
#endif // DLLLIBTEST_GLOBAL_H
3.dlllibtest.h文件
#ifndef DLLLIBTEST_H
#define DLLLIBTEST_H
#include "DllLibTest_global.h"
#if defined(DLLLIBTEST_LIBRARY)
# define DLLLIBTEST_EXPORT Q_DECL_EXPORT
#else
# define DLLLIBTEST_EXPORT Q_DECL_IMPORT
#endif
extern "C"{
DLLLIBTEST_EXPORT int Sum(int a,int b);
extern "C" class DLLLIBTEST_EXPORT DllLibTest
{
public:
DllLibTest();
};
DLLLIBTEST_EXPORT int Sum2(int a,int b);
}
#endif // DLLLIBTEST_H
4.dlllibtest.cpp文件
#include "dlllibtest.h"
DllLibTest::DllLibTest()
{
}
int Sum(int a,int b)
{
return a+b;
}
int Sum2(int a,int b)
{
return a+b;
}
