当符号明确存在于我链接的静态库中时，为什么会出现链接错误? [英] Why do I get link errors when the symbol is clearly present in the static library I link against?

问题描述

我已经决定开始在我的项目中使用ICU，但遗憾的是VS2015正式不受支持(即，开发人员将不兼容列为 http://www.npcglib.org/~stathis/blog/precompiled-icu/.我已经下载了ICU 56 VS15软件包，并尝试编译以下简单程序:

I've decided to start using ICU in my project, but sadly VS2015 is officially unsupported (i.e. the developers list the incompatibility as a known issue). Luckily someone was kind enough to fix the problems on their own and share the binaries with the world: http://www.npcglib.org/~stathis/blog/precompiled-icu/ . I've downloaded the ICU 56 VS15 package and I'm trying to compile the following simple program:

#include <iostream>

#include <unicode\unistr.h>

int main()
{
    auto myStr = icu::UnicodeString::fromUTF8(u8"кошка");
    std::cout << "length: " << myStr.length() << std::endl;

    std::getchar();
    return 0;
}

当我使用编译时导入.lib库时，一切正常，但是我在运行时当然需要DLL库.当我针对静态代码sicuxxx.lib进行编译时，由于某种原因(有六个类似的代码，为简洁起见，省略了它们)我得到了链接错误:

When I use the compile time import .lib libraries, everything works fine, but of course I need the DLL libraries at runtime. When I compile against the static ones, sicuxxx.lib, I get link errors for some reason (there are six similar ones, omitted for brevity):

Error   LNK2001 unresolved external symbol "__declspec(dllimport) private: int __thiscall icu_56::UnicodeString::getShortLength(void)const " (__imp_?getShortLength@UnicodeString@icu_56@@ABEHXZ)

我做了dumpbin /symbols sicuuc.lib，在输出中我可以看到以下内容:

I did dumpbin /symbols sicuuc.lib, and in the output I can see the following:

0E8 00000000 SECT47 notype ()    External     | ?getShortLength@UnicodeString@icu_56@@ABEHXZ (private: int __thiscall icu_56::UnicodeString::getShortLength(void)const )

我的链接器输入如下:kernel32.lib;user32.lib;gdi32.lib;winspool.lib;comdlg32.lib;advapi32.lib;shell32.lib;ole32.lib;oleaut32.lib;uuid.lib;odbc32.lib;odbccp32.lib;sicudt.lib;sicuin.lib;sicuio.lib;sicule.lib;siculx.lib;sicutest.lib;sicutu.lib;sicuuc.lib;.链接程序可以清楚地打开所有文件，因为不会出现无法打开文件"错误.

My linker input is as follows: kernel32.lib;user32.lib;gdi32.lib;winspool.lib;comdlg32.lib;advapi32.lib;shell32.lib;ole32.lib;oleaut32.lib;uuid.lib;odbc32.lib;odbccp32.lib;sicudt.lib;sicuin.lib;sicuio.lib;sicule.lib;siculx.lib;sicutest.lib;sicutu.lib;sicuuc.lib;. All the files can clearly be opened by the linker because no "cannot open file" error appears.

由于dumpbin所示的库中清楚地存在该符号，所以lib.exe为什么在查找它时会遇到问题?

推荐答案

在编译代码时，需要定义U_STATIC_IMPLEMENTATION，以免将ICU功能标记为导入.

You need to define U_STATIC_IMPLEMENTATION when compiling your code so that the ICU functions are not marked as imports.

(您可以看到它当前正在尝试查找的功能被标记为__declspec(dllimport)，与静态库中的功能不匹配.)

(You can see that the function it is currently trying to find is marked as __declspec(dllimport), which doesn't match the one in the static library.)

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