【Qt】通过QtCreator源码学习Qt（二）：跨平台编程

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/u010168781/article/details/84617871

1、Qt对当前平台的判断

在qsystemdetection.h中根据宏定义来判断当前的操作系统，常用的操作系统如下：
Q_OS_WIN、Q_OS_LINUX、Q_OS_MAC、Q_OS_UNIX

qsystemdetection.h源码如下

#ifndef QGLOBAL_H
# include <QtCore/qglobal.h>
#endif

#ifndef QSYSTEMDETECTION_H
#define QSYSTEMDETECTION_H

/*
   The operating system, must be one of: (Q_OS_x)

     DARWIN   - Any Darwin system (macOS, iOS, watchOS, tvOS)
     MACOS    - macOS
     IOS      - iOS
     WATCHOS  - watchOS
     TVOS     - tvOS
     MSDOS    - MS-DOS and Windows
     OS2      - OS/2
     OS2EMX   - XFree86 on OS/2 (not PM)
     WIN32    - Win32 (Windows 2000/XP/Vista/7 and Windows Server 2003/2008)
     WINRT    - WinRT (Windows 8 Runtime)
     CYGWIN   - Cygwin
     SOLARIS  - Sun Solaris
     HPUX     - HP-UX
     ULTRIX   - DEC Ultrix
     LINUX    - Linux [has variants]
     FREEBSD  - FreeBSD [has variants]
     NETBSD   - NetBSD
     OPENBSD  - OpenBSD
     BSDI     - BSD/OS
     INTERIX  - Interix
     IRIX     - SGI Irix
     OSF      - HP Tru64 UNIX
     SCO      - SCO OpenServer 5
     UNIXWARE - UnixWare 7, Open UNIX 8
     AIX      - AIX
     HURD     - GNU Hurd
     DGUX     - DG/UX
     RELIANT  - Reliant UNIX
     DYNIX    - DYNIX/ptx
     QNX      - QNX [has variants]
     QNX6     - QNX RTP 6.1
     LYNX     - LynxOS
     BSD4     - Any BSD 4.4 system
     UNIX     - Any UNIX BSD/SYSV system
     ANDROID  - Android platform
     HAIKU    - Haiku

   The following operating systems have variants:
     LINUX    - both Q_OS_LINUX and Q_OS_ANDROID are defined when building for Android
              - only Q_OS_LINUX is defined if building for other Linux systems
     FREEBSD  - Q_OS_FREEBSD is defined only when building for FreeBSD with a BSD userland
              - Q_OS_FREEBSD_KERNEL is always defined on FreeBSD, even if the userland is from GNU
*/

#if defined(__APPLE__) && (defined(__GNUC__) || defined(__xlC__) || defined(__xlc__))
#  include <TargetConditionals.h>
#  if defined(TARGET_OS_MAC) && TARGET_OS_MAC
#    define Q_OS_DARWIN
#    define Q_OS_BSD4
#    ifdef __LP64__
#      define Q_OS_DARWIN64
#    else
#      define Q_OS_DARWIN32
#    endif
#    if defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE
#      define QT_PLATFORM_UIKIT
#      if defined(TARGET_OS_WATCH) && TARGET_OS_WATCH
#        define Q_OS_WATCHOS
#      elif defined(TARGET_OS_TV) && TARGET_OS_TV
#        define Q_OS_TVOS
#      else
#        // TARGET_OS_IOS is only available in newer SDKs,
#        // so assume any other iOS-based platform is iOS for now
#        define Q_OS_IOS
#      endif
#    else
#      // TARGET_OS_OSX is only available in newer SDKs,
#      // so assume any non iOS-based platform is macOS for now
#      define Q_OS_MACOS
#    endif
#  else
#    error "Qt has not been ported to this Apple platform - see http://www.qt.io/developers"
#  endif
#elif defined(__ANDROID__) || defined(ANDROID)
#  define Q_OS_ANDROID
#  define Q_OS_LINUX
#elif defined(__CYGWIN__)
#  define Q_OS_CYGWIN
#elif !defined(SAG_COM) && (!defined(WINAPI_FAMILY) || WINAPI_FAMILY==WINAPI_FAMILY_DESKTOP_APP) && (defined(WIN64) || defined(_WIN64) || defined(__WIN64__))
#  define Q_OS_WIN32
#  define Q_OS_WIN64
#elif !defined(SAG_COM) && (defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__))
#  if defined(WINAPI_FAMILY)
#    ifndef WINAPI_FAMILY_PC_APP
#      define WINAPI_FAMILY_PC_APP WINAPI_FAMILY_APP
#    endif
#    if defined(WINAPI_FAMILY_PHONE_APP) && WINAPI_FAMILY==WINAPI_FAMILY_PHONE_APP
#      define Q_OS_WINRT
#    elif WINAPI_FAMILY==WINAPI_FAMILY_PC_APP
#      define Q_OS_WINRT
#    else
#      define Q_OS_WIN32
#    endif
#  else
#    define Q_OS_WIN32
#  endif
#elif defined(__sun) || defined(sun)
#  define Q_OS_SOLARIS
#elif defined(hpux) || defined(__hpux)
#  define Q_OS_HPUX
#elif defined(__ultrix) || defined(ultrix)
#  define Q_OS_ULTRIX
#elif defined(sinix)
#  define Q_OS_RELIANT
#elif defined(__native_client__)
#  define Q_OS_NACL
#elif defined(__linux__) || defined(__linux)
#  define Q_OS_LINUX
#elif defined(__FreeBSD__) || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
#  ifndef __FreeBSD_kernel__
#    define Q_OS_FREEBSD
#  endif
#  define Q_OS_FREEBSD_KERNEL
#  define Q_OS_BSD4
#elif defined(__NetBSD__)
#  define Q_OS_NETBSD
#  define Q_OS_BSD4
#elif defined(__OpenBSD__)
#  define Q_OS_OPENBSD
#  define Q_OS_BSD4
#elif defined(__bsdi__)
#  define Q_OS_BSDI
#  define Q_OS_BSD4
#elif defined(__INTERIX)
#  define Q_OS_INTERIX
#  define Q_OS_BSD4
#elif defined(__sgi)
#  define Q_OS_IRIX
#elif defined(__osf__)
#  define Q_OS_OSF
#elif defined(_AIX)
#  define Q_OS_AIX
#elif defined(__Lynx__)
#  define Q_OS_LYNX
#elif defined(__GNU__)
#  define Q_OS_HURD
#elif defined(__DGUX__)
#  define Q_OS_DGUX
#elif defined(__QNXNTO__)
#  define Q_OS_QNX
#elif defined(_SEQUENT_)
#  define Q_OS_DYNIX
#elif defined(_SCO_DS) /* SCO OpenServer 5 + GCC */
#  define Q_OS_SCO
#elif defined(__USLC__) /* all SCO platforms + UDK or OUDK */
#  define Q_OS_UNIXWARE
#elif defined(__svr4__) && defined(i386) /* Open UNIX 8 + GCC */
#  define Q_OS_UNIXWARE
#elif defined(__INTEGRITY)
#  define Q_OS_INTEGRITY
#elif defined(VXWORKS) /* there is no "real" VxWorks define - this has to be set in the mkspec! */
#  define Q_OS_VXWORKS
#elif defined(__HAIKU__)
#  define Q_OS_HAIKU
#elif defined(__MAKEDEPEND__)
#else
#  error "Qt has not been ported to this OS - see http://www.qt-project.org/"
#endif

#if defined(Q_OS_WIN32) || defined(Q_OS_WIN64) || defined(Q_OS_WINRT)
#  define Q_OS_WIN
#endif

#if defined(Q_OS_WIN)
#  undef Q_OS_UNIX
#elif !defined(Q_OS_UNIX)
#  define Q_OS_UNIX
#endif

// Compatibility synonyms
#ifdef Q_OS_DARWIN
#define Q_OS_MAC
#endif
#ifdef Q_OS_DARWIN32
#define Q_OS_MAC32
#endif
#ifdef Q_OS_DARWIN64
#define Q_OS_MAC64
#endif
#ifdef Q_OS_MACOS
#define Q_OS_MACX
#define Q_OS_OSX
#endif

#ifdef Q_OS_DARWIN
#  include <Availability.h>
#  include <AvailabilityMacros.h>
#
#  ifdef Q_OS_MACOS
#    if !defined(__MAC_OS_X_VERSION_MIN_REQUIRED) || __MAC_OS_X_VERSION_MIN_REQUIRED < __MAC_10_6
#       undef __MAC_OS_X_VERSION_MIN_REQUIRED
#       define __MAC_OS_X_VERSION_MIN_REQUIRED __MAC_10_6
#    endif
#    if !defined(MAC_OS_X_VERSION_MIN_REQUIRED) || MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_6
#       undef MAC_OS_X_VERSION_MIN_REQUIRED
#       define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_6
#    endif
#  endif
#
#  // Numerical checks are preferred to named checks, but to be safe
#  // we define the missing version names in case Qt uses them.
#
#  if !defined(__MAC_10_7)
#       define __MAC_10_7 1070
#  endif
#  if !defined(__MAC_10_8)
#       define __MAC_10_8 1080
#  endif
#  if !defined(__MAC_10_9)
#       define __MAC_10_9 1090
#  endif
#  if !defined(__MAC_10_10)
#       define __MAC_10_10 101000
#  endif
#  if !defined(__MAC_10_11)
#       define __MAC_10_11 101100
#  endif
#  if !defined(__MAC_10_12)
#       define __MAC_10_12 101200
#  endif
#  if !defined(__MAC_10_13)
#       define __MAC_10_13 101300
#  endif
#  if !defined(MAC_OS_X_VERSION_10_7)
#       define MAC_OS_X_VERSION_10_7 1070
#  endif
#  if !defined(MAC_OS_X_VERSION_10_8)
#       define MAC_OS_X_VERSION_10_8 1080
#  endif
#  if !defined(MAC_OS_X_VERSION_10_9)
#       define MAC_OS_X_VERSION_10_9 1090
#  endif
#  if !defined(MAC_OS_X_VERSION_10_10)
#       define MAC_OS_X_VERSION_10_10 101000
#  endif
#  if !defined(MAC_OS_X_VERSION_10_11)
#       define MAC_OS_X_VERSION_10_11 101100
#  endif
#  if !defined(MAC_OS_X_VERSION_10_12)
#       define MAC_OS_X_VERSION_10_12 101200
#  endif
#  if !defined(MAC_OS_X_VERSION_10_13)
#       define MAC_OS_X_VERSION_10_13 101300
#  endif
#
#  if !defined(__IPHONE_4_3)
#       define __IPHONE_4_3 40300
#  endif
#  if !defined(__IPHONE_5_0)
#       define __IPHONE_5_0 50000
#  endif
#  if !defined(__IPHONE_5_1)
#       define __IPHONE_5_1 50100
#  endif
#  if !defined(__IPHONE_6_0)
#       define __IPHONE_6_0 60000
#  endif
#  if !defined(__IPHONE_6_1)
#       define __IPHONE_6_1 60100
#  endif
#  if !defined(__IPHONE_7_0)
#       define __IPHONE_7_0 70000
#  endif
#  if !defined(__IPHONE_7_1)
#       define __IPHONE_7_1 70100
#  endif
#  if !defined(__IPHONE_8_0)
#       define __IPHONE_8_0 80000
#  endif
#  if !defined(__IPHONE_8_1)
#       define __IPHONE_8_1 80100
#  endif
#  if !defined(__IPHONE_8_2)
#       define __IPHONE_8_2 80200
#  endif
#  if !defined(__IPHONE_8_3)
#       define __IPHONE_8_3 80300
#  endif
#  if !defined(__IPHONE_8_4)
#       define __IPHONE_8_4 80400
#  endif
#  if !defined(__IPHONE_9_0)
#       define __IPHONE_9_0 90000
#  endif
#  if !defined(__IPHONE_9_1)
#       define __IPHONE_9_1 90100
#  endif
#  if !defined(__IPHONE_9_2)
#       define __IPHONE_9_2 90200
#  endif
#  if !defined(__IPHONE_9_3)
#       define __IPHONE_9_3 90300
#  endif
#  if !defined(__IPHONE_10_0)
#       define __IPHONE_10_0 100000
#  endif
#  if !defined(__IPHONE_10_1)
#       define __IPHONE_10_1 100100
#  endif
#  if !defined(__IPHONE_10_2)
#       define __IPHONE_10_2 100200
#  endif
#  if !defined(__IPHONE_10_3)
#       define __IPHONE_10_3 100300
#  endif
#  if !defined(__IPHONE_11_0)
#       define __IPHONE_11_0 110000
#  endif
#endif

#ifdef __LSB_VERSION__
#  if __LSB_VERSION__ < 40
#    error "This version of the Linux Standard Base is unsupported"
#  endif
#ifndef QT_LINUXBASE
#  define QT_LINUXBASE
#endif
#endif

#endif // QSYSTEMDETECTION_H

2、QtCreator中对跨平台的判断

QtCreator中又对Qt定义的宏做了一次转换，将宏定义转换成对应的enum，源码如下；

enum OsType { OsTypeWindows, OsTypeLinux, OsTypeMac, OsTypeOtherUnix, OsTypeOther };
    static constexpr OsType hostOs()
    {
#if defined(Q_OS_WIN)
        return OsTypeWindows;
#elif defined(Q_OS_LINUX)
        return OsTypeLinux;
#elif defined(Q_OS_MAC)
        return OsTypeMac;
#elif defined(Q_OS_UNIX)
        return OsTypeOtherUnix;
#else
        return OsTypeOther;
#endif
    }
    
    static constexpr bool isWindowsHost() { return hostOs() == OsTypeWindows; }
    static constexpr bool isLinuxHost() { return hostOs() == OsTypeLinux; }
    static constexpr bool isMacHost() { return hostOs() == OsTypeMac; }
    static constexpr bool isAnyUnixHost()
    {
#ifdef Q_OS_UNIX
        return true;
#else
        return false;
#endif
    }
}

3、QtCreator在pro中跨平台编码

在pro中根据不同的操作系统添加不同的文件，demo如下

unix:SOURCES += $$PWD/qtlockedfile_unix.cpp
win32:SOURCES += $$PWD/qtlockedfile_win.cpp