目录

一、使用Qt编译C动态库

二、使用QLibrary调用共享库

一、使用Qt编译C动态库

    使用Qt新建一个C项目 cbb_frame,在项目中我们声明和定义两个函数，并导出函数。在cbb_mylog中我们使用了函数指针，这里为啥这样干，先埋个伏笔，下一篇我们再来具体交流下。

// cbb_frame.pro

TEMPLATE = lib #app
CONFIG += console  \
          # static \
          c++11 \
          shared\
          dll

CONFIG -= app_bundle
CONFIG -= qt

CONFIG     += no_debug_release         # 不会生成debug 和 release 文件目录
DESTDIR     = $$PWD/./_build/bin       # 指定编译最终文件的生成路径
OBJECTS_DIR = $$PWD/./_build/obj       # obj中间文件存放路径
MOC_DIR     = $$PWD/./_build/moc       # moc中间文件路径
RCC_DIR     = $$PWD/./_build/rcc       # rcc资源文件路径
UI_DIR      = $$PWD/./_build/ui        # ui_XXX.h 中间文件存放路径

DEFINES += CBB_LIBRARY                 # 导出

SOURCES += \
    cbb_mylog.cpp

HEADERS += \
    cbb_mylog.h

// cbb_mylog.h

#ifndef CBB_MYLOG_H
#define CBB_MYLOG_H


#if defined(CBB_LIBRARY)
#  define _API extern "C" __declspec(dllexport)
#else
#  define _API extern "C" __declspec(dllimport)
#endif

typedef void (*cbb_func)(void* ref,int len);

typedef struct cbb_data
{
    cbb_func func;
    void* ref;
    int len;
}cbb_t,*p_cbb;

enum log_level{
    LEVEL1,
    LEVEL2,
    LEVEL3
};

_API void cbb_mylog(p_cbb pb,log_level level,char* f,...);
_API int add(int x,int y);

#endif // CBB_MYLOG_H

// cbb_mylog.cpp

#include "cbb_mylog.h"
#include <stdio.h>
#include <stdarg.h>

void cbb_mylog(p_cbb pb, log_level level, char *f,...)
{
    if ( nullptr != pb ) pb->func(pb->ref,pb->len);

    char buf[4000] = {0};
    va_list args;
    va_start(args, f);
    vsprintf(buf, f,args);
    va_end(args);

    printf("%s\n",buf);
}

int add(int x, int y)
{
    return x+y;
}

二、使用QLibrary调用共享库

我们新建一个测试项目 LoadLib_Test

// LoadLib_Test.pro

QT -= gui

CONFIG += c++11 console
CONFIG -= app_bundle

CONFIG     += no_debug_release         # 不会生成debug 和 release 文件目录
DESTDIR     = $$PWD/./_build/bin       # 指定编译最终文件的生成路径
OBJECTS_DIR = $$PWD/./_build/obj       # obj中间文件存放路径
MOC_DIR     = $$PWD/./_build/moc       # moc中间文件路径
RCC_DIR     = $$PWD/./_build/rcc       # rcc资源文件路径
UI_DIR      = $$PWD/./_build/ui        # ui_XXX.h 中间文件存放路径

# 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 += \
        main.cpp

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

#include <QCoreApplication>
#include <QLibrary>
#include <QDebug>

typedef void (*cbb_func)(void* ref,int len);

typedef struct cbb_data
{
    cbb_func func;
    void* ref;
    int len;
}cbb_t,*p_cbb;

enum log_level{
    LEVEL1,
    LEVEL2,
    LEVEL3
};

typedef void (*cb_func)(p_cbb pb,log_level level,char* f,...);
typedef int (*padd)(int x,int y);

void show_help(void* ref,int len){
    printf("%s %d show_help \n",__FILE__,__LINE__);
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QString library_path = QCoreApplication::applicationDirPath() + "/cbb_frame.dll";
    QLibrary* L = new QLibrary(library_path);

    if( nullptr == L) return -1;

    if(! L->load()){
        qDebug() << "[error:]" << L->errorString();
        delete L;
        L = NULL;
    }

    // ![1]
    cb_func myprintf = (cb_func)L->resolve("cbb_mylog");

    cbb_t cbb = {show_help,NULL,0};
    myprintf(&cbb,LEVEL1,"%s","this is a call back frame between library and customer program");

    // ![2]
    padd add_func = (padd)L->resolve("add");
    qDebug() << " add_func(3,7) = " << add_func(3,7);

    L->unload();

    return a.exec();
}

输出：

main.cpp 24 show_help  # 在动态库中调用了测试用例中的help_show()方法
this is a call back frame between library and customer program
add_func(3,7) =  10