Qt5.15.0 升级至 Qt5.15.9 遇到的一些错误

按照之前我写的文章教程，可以很简单的编译出静态库（仅供学习交流）

• 编译 windows 上的 qt 静态库

编译出静态库后，替换旧版本的库，见我另一篇文章教程

• VS2019 配置 QT 库

之所以没有直接上 Qt6.0 以上的版本，是因为 Qt6.0 对比 Qt5 删减了不少东西（我之前已经测试过了），这就导致项目要有比较大的改动，所以暂时没有特别要换的需求

Qt5.15.9 的静态库版本是今年四月份（2023.4.6）官方才放出的，修复了不少 bug，其中包括我之前遇到的一个字体 bug，见下面的文章，

• QT 无法识别某些字体导致程序启动失败

在编译项目时，遇到了两个比较棘手的问题，第一个是库中函数重定义问题，第二个是找不到对应的库

下面说说这两个问题的解决方法，

第一个报错，

1>zlibd.lib(crc32.obj) : error LNK2005: _crc32_combine_op already defined in Qt5Cored.lib(crc32.obj)
1>zlibd.lib(crc32.obj) : error LNK2005: _crc32_combine_gen already defined in Qt5Cored.lib(crc32.obj)
1>zlibd.lib(crc32.obj) : error LNK2005: _crc32_combine_gen64 already defined in Qt5Cored.lib(crc32.obj)
1>******************************************** : fatal error LNK1169: one or more multiply defined symbols found

因为这两个库我都要用到，所以就使用 /FORCE:MULTIPLE  强行忽略第二个定义

结果，

zlibd.lib(crc32.obj) : warning LNK4006: _crc32_combine_op already defined in Qt5Cored.lib(crc32.obj); second definition ignored
1>zlibd.lib(crc32.obj) : warning LNK4006: _crc32_combine_gen already defined in Qt5Cored.lib(crc32.obj); second definition ignored
1>zlibd.lib(crc32.obj) : warning LNK4006: _crc32_combine_gen64 already defined in Qt5Cored.lib(crc32.obj); second definition ignored

补充：

之所以出现重定义，是因为 Qt5.15.9 内部用的是 1.2.12 的 zlib 版本，该 zlib 版本存在 bug，见，

• crc32 functions produce errors when building 1.2.12 zlibstat on Windows

该 bug 已在 1.2.13 中修复，我们也可以先手动改下 crc32.c 源文件再重新编译 lib

注意：可能存在即使修改了也仍然报重定义的错误，所以我是将 crc32.c 中这些函数注释了，免得链接到这里，暂时可以解决

第二个报错，

qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_std_error referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_CreateCompress referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_CreateDecompress referenced in function "public: bool __thiscall QJpegHandlerPrivate::readJpegHeader(class QIODevice *)" (?readJpegHeader@QJpegHandlerPrivate@@QAE_NPAVQIODevice@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_destroy_compress referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_destroy_decompress referenced in function "public: __thiscall QJpegHandlerPrivate::~QJpegHandlerPrivate(void)" (??1QJpegHandlerPrivate@@QAE@XZ)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_set_defaults referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_set_quality referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_simple_progression referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_start_compress referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_write_scanlines referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_finish_compress referenced in function "bool __cdecl do_write_jpeg_image(struct jpeg_compress_struct &,unsigned char * *,class QImage const &,class QIODevice *,int,class QString const &,bool,bool)" (?do_write_jpeg_image@@YA_NAAUjpeg_compress_struct@@PAPAEABVQImage@@PAVQIODevice@@HABVQString@@_N5@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_write_marker referenced in function "void __cdecl set_text(class QImage const &,struct jpeg_compress_struct *,class QString const &)" (?set_text@@YAXABVQImage@@PAUjpeg_compress_struct@@ABVQString@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_read_header referenced in function "public: bool __thiscall QJpegHandlerPrivate::readJpegHeader(class QIODevice *)" (?readJpegHeader@QJpegHandlerPrivate@@QAE_NPAVQIODevice@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_start_decompress referenced in function "bool __cdecl read_jpeg_image(class QImage *,class QSize,class QRect,class QRect,int,void (__fastcall*)(unsigned int *,unsigned char const *,int),struct jpeg_decompress_struct *,struct my_error_mgr *)" (?read_jpeg_image@@YA_NPAVQImage@@VQSize@@VQRect@@2HP6IXPAIPBEH@ZPAUjpeg_decompress_struct@@PAUmy_error_mgr@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_read_scanlines referenced in function "bool __cdecl read_jpeg_image(class QImage *,class QSize,class QRect,class QRect,int,void (__fastcall*)(unsigned int *,unsigned char const *,int),struct jpeg_decompress_struct *,struct my_error_mgr *)" (?read_jpeg_image@@YA_NPAVQImage@@VQSize@@VQRect@@2HP6IXPAIPBEH@ZPAUjpeg_decompress_struct@@PAUmy_error_mgr@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_finish_decompress referenced in function "bool __cdecl read_jpeg_image(class QImage *,class QSize,class QRect,class QRect,int,void (__fastcall*)(unsigned int *,unsigned char const *,int),struct jpeg_decompress_struct *,struct my_error_mgr *)" (?read_jpeg_image@@YA_NPAVQImage@@VQSize@@VQRect@@2HP6IXPAIPBEH@ZPAUjpeg_decompress_struct@@PAUmy_error_mgr@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_calc_output_dimensions referenced in function "bool __cdecl read_jpeg_size(int &,int &,struct jpeg_decompress_struct *)" (?read_jpeg_size@@YA_NAAH0PAUjpeg_decompress_struct@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_save_markers referenced in function "public: bool __thiscall QJpegHandlerPrivate::readJpegHeader(class QIODevice *)" (?readJpegHeader@QJpegHandlerPrivate@@QAE_NPAVQIODevice@@@Z)
1>qjpegd.lib(qjpeghandler.obj) : error LNK2019: unresolved external symbol _jpeg_resync_to_restart referenced in function "public: __thiscall my_jpeg_source_mgr::my_jpeg_source_mgr(class QIODevice *)" (??0my_jpeg_source_mgr@@QAE@PAVQIODevice@@@Z)

LNK2019 的报错很简单明了，就是链接时没有找到对应函数的符号文件，导致链接失败，然后报错

结合新生成的 lib 文件，我第一感觉就是 Qt5.15.9 将这些函数删减了

lib 文件大小删减了三分之二左右，故项目中原先依赖这块部分的函数都找不到符号文件了

目前我的解决方案是将项目中这块依赖代码删掉（这些代码用于 jpeg 的图片插件），后续测试看看有没有问题，先保证项目能编译成功

这两个错误解决后，项目再次 0 error，并且字体 bug 不出现了

---

更新：

注释了 QJpegPlugin 后，Qt 将无法加载 jpeg 格式图片，所以不需要注释掉

不注释会报错的解决方法见：Qt 加载 libjpeg 库出现“长跳转已经运行”错误

相关：

• https://doc.qt.io/qt-6/qtgui-attribution-libjpeg.html
• Qt Configure Options
• https://code.qt.io/cgit/qt/qtreleasenotes.git/about/qt/5.15.9/release-note.md#qtbase