迁移到MSYS2 与 Qt 工具链注意的几个事情（注意链接顺序，并且人造mingw工具链所没有的局部midl.exe命令）

     Microsoft Visual Studio 2015社区版提供了强大的开发体验，且 Qt 提供了预编译版本。然而，由于客户提出兼容Windows XP ~ Windows 8.1 这样宽泛的环境要求，使得我们不得不考虑更换工具链。经过反复对比测试，在Mingw32, Cygwin,  MSYS2, Visual Studio 2010几个工具链中，综合性能、未来的可持续性、中文支持以及第三方库支持（比如qwt），认为MSYS2较为合适。在后续复杂的迁移过程中，基本是平顺的，但也遇到了一些问题，这里做个记录。

     1、ActiveQt COM/OLE 支持有问题，需要额外设置编译参数

      我们有个子项目需要生成一个ActiveX控件，使用到了 QAxContainer模块。在编译时，报告了上百个编译错误，提示找不到 libole32.a, libuuid.a 等库中包含的符号。经过简单分析，特别是MakeFile中的编译器指令提示，MSYS2没有正确处理ActiveQt的链接选项。具体说来，由于g++在链接时，符号依赖项查找遵循从左至右的顺序，如果设置不当，会导致诡异的链接错误，请参考这篇文章。 

      知道了这个问题，我们手工在pro文件中加入下面的内容：

    

LIBS += -lQt5AxServer -lQt5AxBase -lole32 -loleaut32 -luser32 -lgdi32 -ladvapi32 -luuid

错误竟然依旧！继续观察qmake出来的MakeFile，发现-lQt5Ax* 都被放到了最后。一拍脑袋，怎么忘记了， qmake 在产生Makefile对相同名称的库进行合并，会改变其原有的顺序这个坑~！于是，把需要使用 QAxServer 模块的工程改成这样：

win32-g++{
    CONFIG += no_lflags_merge
    LIBS += -lQt5AxServer -lQt5AxBase -lole32 -loleaut32 -luser32 -lgdi32 -ladvapi32 -luuid
}

        把需要使用 QAxContainer 模块的工程改成这样：

win32-g++{
    CONFIG += no_lflags_merge
    LIBS += -lQt5AxContainer -lQt5AxBase -lole32 -loleaut32 -luser32 -lgdi32 -ladvapi32 -luuid
}

    no_lflags_merge 表示不进行库合并和排序（排序是合并的副作用，估计内部合并时用了类似set 之类的类stl容器），这样，Makfile中，Qt5Ax*库就位于系统库之前了！这一点在Qt官方Mingw32安装版里是调整好了的。

     修改后，链接通过，但是，Post Link 流程出错。

    

    2. 解决参数转译符冲突

      链接后，第一个问题是无法生成IDL文件。考察编译输出命令行，发现对 idc.exe 调用时，传参数使用的是 windows 参数转译符 "/"。然而，在msys2环境里，"/"不是unix命令行的合法参数转译符，应该用“-”（减号）才对。不要紧，这个编译后事件的命令全部存储在 mingw32(64)/share/qt5/mkspecs/features/win32/idcidl.prf 里。这个文件的内容如下：

...
!qaxserver_no_postlink {
    !isEmpty(QMAKE_POST_LINK):QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_NEWLINE)
    QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} /idl $ ${ACTIVEQT_OUTPUT}.idl -version $ ${ACTIVEQT_VERSION}$ ${ACTIVEQT_NEWLINE})
    !isEmpty(RC_FILE) {
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDL "$ ${ACTIVEQT_OUTPUT}.idl" /nologo /tlb "$ ${ACTIVEQT_OUTPUT}.tlb"$ $ACTIVEQT_NEWLINE)
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} -tlb $ ${ACTIVEQT_OUTPUT}.tlb$ $ACTIVEQT_NEWLINE)
    } else {
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDL "$ ${ACTIVEQT_OUTPUT}.idl" /nologo /tlb "$ ${ACTIVEQT_TLBOUT}"$ $ACTIVEQT_NEWLINE)
        message("No rc-file linked into project; type library will be a separate file.")
    }
    !qaxserver_no_register:
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} /regserver)
    QMAKE_CLEAN += $ ${ACTIVEQT_OUTPUT}.idl $ ${ACTIVEQT_OUTPUT}.tlb
}

二话不说，全部改为"-"

!qaxserver_no_postlink {
    !isEmpty(QMAKE_POST_LINK):QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_NEWLINE)
    QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} -idl $ ${ACTIVEQT_OUTPUT}.idl -version $ ${ACTIVEQT_VERSION}$ ${ACTIVEQT_NEWLINE})
    !isEmpty(RC_FILE) {
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDL "$ ${ACTIVEQT_OUTPUT}.idl" -nologo -tlb "$ ${ACTIVEQT_OUTPUT}.tlb"$ $ACTIVEQT_NEWLINE)
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} -tlb $ ${ACTIVEQT_OUTPUT}.tlb$ $ACTIVEQT_NEWLINE)
    } else {
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDL "$ ${ACTIVEQT_OUTPUT}.idl" -nologo -tlb "$ ${ACTIVEQT_TLBOUT}"$ $ACTIVEQT_NEWLINE)
        message("No rc-file linked into project; type library will be a separate file.")
    }
    !qaxserver_no_register:
        QMAKE_POST_LINK += $ $quote($ $ACTIVEQT_IDC $ ${ACTIVEQT_TARGET} -regserver)
    QMAKE_CLEAN += $ ${ACTIVEQT_OUTPUT}.idl $ ${ACTIVEQT_OUTPUT}.tlb
}

修改后，再次重新编译（要重新编译才能触发编译后事件），idl 顺利产生。

      可是，接着问题又大了，msys2 的工具链里没有 midl.exe。这个工具是windows SDK 的一部分，且需要Visual C++的 cl.exe。先是尝试在PATH里加入路径，但没有成功。除非彻底加入vcvars32.bat的所有设置，否则无法通过。这个问题有办法：

    3. 为Mingw32 环境提供midl.exe支持

      前文书，midl.exe 是 windows SDK中的工具，这个工具依赖Visual C++编译器。然而，在MingW工具链中，默认是无法调用VC编译器的。为了给Mingw32-make创造出一个局部的VC编译环境，新建一个简单的控制台外壳，名字也叫“midl.exe”，在内部调用 vcvars32.bat并把命令行参数传给真正的 midl.exe即可:

pro文件，控制台Qt应用:

QT += core
QT -= gui

CONFIG += c++11

TARGET = midl
CONFIG += console
CONFIG -= app_bundle

TEMPLATE = app

SOURCES += main.cpp

唯一的代码文件，main.cpp:

#include <QCoreApplication>
#include <QString>
#include <QSettings>
#include <QDir>
#include <QProcess>
#include <QStringList>
#include <QDebug>
#include <stdlib.h>
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QString exeName = a.applicationName();
    //0. the exe name and ini filename should be  stored together.
    QString iniFile = a.applicationFilePath() + ".ini";
    QSettings settings(iniFile,QSettings::IniFormat);
    //1.get the current directory
    QString strCurrentDir = QDir::current().absolutePath();
    //2.get the visual studio vcvars32 path and raw EXE path
    QString vcvarsPath = settings.value("SETTINGS/VCVARS","D:\Microsoft Visual Studio 10.0\VC\bin\vcvars32.bat")
            .toString();
    QString exeDir = settings.value("SETTINGS/EXEDIR","C:\Program Files (x86)\Windows Kits\8.1\bin\x86")
            .toString();
    //3.Make the cmd target
    QString cmd ;
    //3.1. call vc vars to
    //  cmd += " && ";
    cmd += "CALL ";
    cmd += """ + vcvarsPath + """;
    //3.2. chdir back to current
    cmd += " && ";
    cmd += "CD /D "" + strCurrentDir.replace("/","\") + """;
    //3.3. call exeName with args
    cmd += " && ";
    cmd += """ + exeDir + "\" + exeName + "" ";

    for(int i=1;i<argc;++i)
        cmd += argv[i] + QString(" ");

    settings.setValue("SETTINGS/VCVARS",vcvarsPath);
    settings.setValue("SETTINGS/EXEDIR",exeDir);

    //4. display and exe the cmd
    puts(cmd.toStdString().c_str());
    int ret = system(cmd.toStdString().c_str());
    a.exit(0);
    return ret;
}

默认的VC配置可能和实际的不符合，不要紧，只要在 midl.exe （壳子）同文件夹下设置midl.exe.ini即可：

[SETTINGS]
VCVARS=D:\Microsoft Visual Studio 10.0\VC\bin\vcvars32.bat
EXEDIR=C:\Program Files (x86)\Windows Kits\8.1\bin\x86

修改这个参数即可。VCVARS即是vc编译器批处理文件的位置，EXEDIR是真的midl.exe的文件夹。

4. 试试看！

 二话不说，开始编译，OK!

g++ -Wl,-s -shared -Wl,-subsystem,windows -mthreads -Wl,--out-implib,../bin/libqtaxviewer_planetosm.dll.a -Wl,../../qtv.planet/qtviewer_planetosm/qtaxviewer_planetosm.def -o ../bin/qtaxviewer_planetosm.dll object_script.qtaxviewer_planetosm.Release  -lglu32 -lopengl32 -lgdi32 -luser32 -lQt5AxServer -lQt5AxBase -lole32 -loleaut32 -luser32 -lgdi32 -ladvapi32 -luuid -lQt5AxServer -lQt5AxBase -lQt5Widgets -lQt5Gui -lQt5Network -lQt5Core
/D/msys64/mingw32/bin/idc.exe ../bin/qtaxviewer_planetosm.dll -idl release//qtaxviewer_planetosm.idl -version 1.0

release\qtaxviewer_planetosm.idl

midl release//qtaxviewer_planetosm.idl -nologo -tlb release//qtaxviewer_planetosm.tlb

Setting environment for using Microsoft Visual Studio 2010 x86 tools.
Processing release\qtaxviewer_planetosm.idl
qtaxviewer_planetosm.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeocidl.idl
ocidl.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeoleidl.idl
oleidl.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeobjidl.idl
objidl.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeunknwn.idl
unknwn.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludewtypes.idl
wtypes.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeasetsd.h
basetsd.h
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeguiddef.h
guiddef.h
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeoaidl.idl
oaidl.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeservprov.idl
servprov.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeurlmon.idl
urlmon.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludemsxml.idl
msxml.idl
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeoaidl.acf
oaidl.acf
Processing C:Program Files (x86)Microsoft SDKsWindowsv7.0Aincludeocidl.acf
ocidl.acf
CALL "D:Microsoft Visual Studio 10.0VCinvcvars32.bat" && CD /D "D:documentsQtuild-qplanetosm-Desktop_Qt_MinGW_w64_32bit_MSYS2-Releaseqtviewer_planetosm" && "C:Program Files (x86)Windows Kits8.1inx86midl" release//qtaxviewer_planetosm.idl -nologo -tlb release//qtaxviewer_planetosm.tlb
/D/msys64/mingw32/bin/idc.exe ../bin/qtaxviewer_planetosm.dll -tlb release//qtaxviewer_planetosm.tlb
Type library attached to D:documentsQtuild-qplanetosm-Desktop_Qt_MinGW_w64_32bit_MSYS2-Releaseinqtaxviewer_planetosm.dll.
/D/msys64/mingw32/bin/idc.exe ../bin/qtaxviewer_planetosm.dll -regserver
Server registered successfully!
mingw32-make[2]: Leaving directory 'D:/documents/Qt/build-qplanetosm-Desktop_Qt_MinGW_w64_32bit_MSYS2-Release/qtviewer_planetosm'
mingw32-make[1]: Leaving directory 'D:/documents/Qt/build-qplanetosm-Desktop_Qt_MinGW_w64_32bit_MSYS2-Release/qtviewer_planetosm'
09:57:52: 进程"D:msys64mingw32inmingw32-make.exe"正常退出。
09:57:52: Elapsed time: 01:26.

http://blog.csdn.net/goldenhawking/article/details/51125604