Win10下使用CMake编译libcurl报LNK2019未解析符号错误如何解决

我尝试在Win10系统下基于CMake编译项目中的libcurl，目前libcurl部分的配置如下：

link_directories("C:/Program Files/OpenSSL-Win64-1_1_1/lib")
link_directories("C:/Program Files/OpenSSL-Win64-1_1_1")
list(APPEND CMAKE_PREFIX_PATH ${CMAKE_CURRENT_SOURCE_DIR}/out/build/x64-Debug/libssh2-1.10.0/src)
add_subdirectory(curl-7.80.0)

执行编译时触发如下错误：

Creating library C:/PATH/build/curl-7.80.0/lib/Debug/libcurl-d_imp.lib and object C:/PATH/build/curl-7.80.0/lib/Debug/libcurl-d_imp.exp
libssh2.obj : error LNK2019: unresolved external symbol libssh2_init referenced in function Curl_ssh_init [C:\PATH\curl-7.80.0\build\lib\libcurl.vcxproj]
libssh2.obj : error LNK2019: unresolved external symbol libssh2_exit referenced in function Curl_ssh_cleanup
[C:\PATH\curl-7.80.0\build\lib\libcurl.vcxproj]
libssh2.obj : error LNK2019: unresolved external symbol libssh2_session_init_ex referenced in function ssh_force_knownhost_key_type
[C:\PATH\curl-7.80.0\build\lib\libcurl.vcxproj]
libssh2.obj : error LNK2019: unresolved external symbol libssh2_session_abstract referenced in function sftp_perform
[C:\PATH\curl-7.80.0\build\lib\libcurl.vcxproj]

我使用的OpenSSL通过slproweb提供的Win32OpenSSL安装包安装，我对CMake的了解仅够编译普通自有项目，这个问题超出了我的知识范围，恳请大家提供帮助。

补充1：CMake生成的实际链接命令 #

Link:
C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.29.30133\bin\HostX64\x64\link.exe /ERRORREPORT:QUEUE /OUT:"C:\PATH\bin\64bit_\Debug\libcurl-d.dll" /INCREMENTAL /ILK:"libcurl.dir\Debug\libcurl-d.ilk" /NOLOGO /LIBPATH:"C:/Program Files/OpenSSL-Win64-1_1_1/lib" /LIBPATH:"C:/Program Files/OpenSSL-Win64-1_1_1/lib/Debug" /LIBPATH:"C:/Program Files/OpenSSL-Win64-1_1_1" /LIBPATH:"C:/Program Files/OpenSSL-Win64-1_1_1/Debug" /LIBPATH:"C:/PATH/out/build/x64-Debug/libssh2-1.10.0/src" /LIBPATH:"C:/PATH/out/build/x64-Debug/libssh2-1.10.0/src/Debug" /LIBPATH:"C:/PATH/out/build/x64-Debug/libssh2-1.10.0" /LIBPATH:"C:/PATH/out/build/x64-Debug/libssh2-1.10.0/Debug" wldap32.lib winmm.lib ws2_32.lib "......\out\build\x64-Debug\libssh2-1.10.0\src\libssh2.lib" advapi32.lib crypt32.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /manifest:embed /DEBUG /PDB:"C:/PATH/bin/64bit_/Debug/libcurl-d.pdb" /SUBSYSTEM:CONSOLE /TLBID:1 /DYNAMICBASE /NXCOMPAT /IMPLIB:"C:/PATH/build/curl-7.80.0/lib/Debug/libcurl-d_imp.lib" /MACHINE:X64 /machine:x64 /DLL libcurl.dir\Debug\libcurl.res

补充2：针对libssh2_exit执行dumpbin的结果 #

00C 00000050 SECT4 notype () External | libssh2_exit
01B 00000008 SECT5 notype Static | $unwind$libssh2_exit
01C 0000000C SECT6 notype Static | $pdata$libssh2_exit

这个报错的核心原因是libcurl编译时对libssh2的符号识别和实际libssh2库的编译配置不匹配，按以下步骤排查修复即可：

1. 添加静态编译标记
   你使用的是静态编译的libssh2库，但libcurl默认会按照动态库的规则去查找带dll导入前缀的libssh2符号，导致符号不匹配。在add_subdirectory(curl-7.80.0)之前添加如下配置，强制指定静态链接libssh2：

# 启用libcurl的ssh支持
set(CURL_USE_LIBSSH2 ON CACHE BOOL "enable libssh2" FORCE)
# 告诉curl当前用的是静态版libssh2
add_compile_definitions(LIBSSH2_STATIC)
# 补充libssh2的头文件目录，替换为你实际的libssh2源码include路径和编译输出的头文件路径
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/libssh2-1.10.0/include ${CMAKE_CURRENT_SOURCE_DIR}/out/build/x64-Debug/libssh2-1.10.0/include)

2. 统一运行库配置
   检查libssh2和libcurl的编译选项，确保二者使用完全相同的CRT运行库：Debug模式下统一为/MDd（动态运行库）或/MTd（静态运行库），Release模式下对应为/MD或/MT，避免运行库不匹配导致的符号冲突。
3. 清理缓存重新编译
   删除CMake生成的build目录所有内容，重新执行CMake生成命令、编译命令，避免旧缓存配置干扰。

如果上述操作后仍有问题，可以用find_package显式导入libssh2目标，让CMake自动处理依赖配置，替换你原来的CMAKE_PREFIX_PATH配置即可：

find_package(Libssh2 REQUIRED PATHS ${CMAKE_CURRENT_SOURCE_DIR}/out/build/x64-Debug/libssh2-1.10.0)

内容的提问来源于stack exchange，提问作者Narase