Linking Crypto++ fails when building a C++ project using CMake

问题

I have the following project structure:

myexec/
|-main.cpp
|-hashing.cpp
|-hashing.h
|-CMakeLists.txt

My little software needs Crypto++ whose latest version I built under this path:

C:\Users\myuser\cryptopp

CMakeLists.txt is:

cmake_minimum_required (VERSION 3.8)

project ("MyExec")

add_executable(MyExec "main.cpp", "hashing.h", "hashing.cpp")

find_library(CRYPTOPP_LIB cryptopp "C:/Users/myuser/cryptopp/Win32/DLL_Output/Debug")
target_link_libraries(MyExec PUBLIC "${CRYPTOPP_LIB}")

target_include_directories(MyExec PUBLIC "C:/Users/myuser/cryptopp")

hashing.cpp is:

#define CRYPTOPP_ENABLE_NAMESPACE_WEAK 1 // Needed to use MD5 in Crypto++

#include <cryptlib.h>
#include <md5.h>

#include "Hashing.h"

using namespace CryptoPP;

std::string get_hash(const std::string& str)
{
    std::string digest;
    Weak::MD5 hash;

    hash.Update((const byte*)(str.data()), str.size());
    digest.resize(hash.DIGESTSIZE);
    hash.Final((byte*)&digest[0]);

    return digest;
}

Problem

As I compile this in VS 2019 Community on my Win10 x64 machine, I get this linking error:

C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: __cdecl CryptoPP::Algorithm::Algorithm(bool)" (??0Algorithm@CryptoPP@@QEAA@_N@Z) referenced in function "public: __cdecl CryptoPP::HashTransformation::HashTransformation(void)" (??0HashTransformation@CryptoPP@@QEAA@XZ)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2001: unresolved external symbol "public: virtual bool __cdecl CryptoPP::HashTransformation::TruncatedVerify(unsigned char const *,unsigned __int64)" (?TruncatedVerify@HashTransformation@CryptoPP@@UEAA_NPEBE_K@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: virtual void __cdecl CryptoPP::IteratedHashBase<unsigned int,class CryptoPP::HashTransformation>::Update(unsigned char const *,unsigned __int64)" (?Update@?$IteratedHashBase@IVHashTransformation@CryptoPP@@@CryptoPP@@UEAAXPEBE_K@Z) referenced in function "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl get_hash(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?get_hash@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@AEBV34@@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2001: unresolved external symbol "public: virtual unsigned char * __cdecl CryptoPP::IteratedHashBase<unsigned int,class CryptoPP::HashTransformation>::CreateUpdateSpace(unsigned __int64 &)" (?CreateUpdateSpace@?$IteratedHashBase@IVHashTransformation@CryptoPP@@@CryptoPP@@UEAAPEAEAEA_K@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2001: unresolved external symbol "public: virtual void __cdecl CryptoPP::IteratedHashBase<unsigned int,class CryptoPP::HashTransformation>::Restart(void)" (?Restart@?$IteratedHashBase@IVHashTransformation@CryptoPP@@@CryptoPP@@UEAAXXZ)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2001: unresolved external symbol "public: virtual void __cdecl CryptoPP::IteratedHashBase<unsigned int,class CryptoPP::HashTransformation>::TruncatedFinal(unsigned char *,unsigned __int64)" (?TruncatedFinal@?$IteratedHashBase@IVHashTransformation@CryptoPP@@@CryptoPP@@UEAAXPEAE_K@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2001: unresolved external symbol "protected: virtual unsigned __int64 __cdecl CryptoPP::IteratedHashBase<unsigned int,class CryptoPP::HashTransformation>::HashMultipleBlocks(unsigned int const *,unsigned __int64)" (?HashMultipleBlocks@?$IteratedHashBase@IVHashTransformation@CryptoPP@@@CryptoPP@@MEAA_KPEBI_K@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: static void __cdecl CryptoPP::Weak1::MD5::InitState(unsigned int *)" (?InitState@MD5@Weak1@CryptoPP@@SAXPEAI@Z) referenced in function "protected: virtual void __cdecl CryptoPP::IteratedHashWithStaticTransform<unsigned int,struct CryptoPP::EnumToType<enum CryptoPP::ByteOrder,0>,64,16,class CryptoPP::Weak1::MD5,0,0>::Init(void)" (?Init@?$IteratedHashWithStaticTransform@IU?$EnumToType@W4ByteOrder@CryptoPP@@$0A@@CryptoPP@@$0EA@$0BA@VMD5@Weak1@2@$0A@$0A@@CryptoPP@@MEAAXXZ)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: static void __cdecl CryptoPP::Weak1::MD5::Transform(unsigned int *,unsigned int const *)" (?Transform@MD5@Weak1@CryptoPP@@SAXPEAIPEBI@Z) referenced in function "protected: virtual void __cdecl CryptoPP::IteratedHashWithStaticTransform<unsigned int,struct CryptoPP::EnumToType<enum CryptoPP::ByteOrder,0>,64,16,class CryptoPP::Weak1::MD5,0,0>::HashEndianCorrectedBlock(unsigned int const *)" (?HashEndianCorrectedBlock@?$IteratedHashWithStaticTransform@IU?$EnumToType@W4ByteOrder@CryptoPP@@$0A@@CryptoPP@@$0EA@$0BA@VMD5@Weak1@2@$0A@$0A@@CryptoPP@@MEAAXPEBI@Z)
C:\Users\myuser\cryptopp\Win32\DLL_Output\Debug\cryptopp.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\myexec.exe : fatal error LNK1120: 9 unresolved externals
  ninja: build stopped: subcommand failed.

What am I doing wrong here?

Edit

After good feedback from @botje and @nelsonsule, I fixed the x64 issue:

find_library(CRYPTOPP_LIB cryptopp "C:/Users/myuser/cryptopp/x64/DLL_Output/Release")

This is now causing the arch mismatch warning to go away, but I will get 2 linking errors:

C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: static void __cdecl CryptoPP::Weak1::MD5::InitState(unsigned int *)" (?InitState@MD5@Weak1@CryptoPP@@SAXPEAI@Z) referenced in function "protected: virtual void __cdecl CryptoPP::IteratedHashWithStaticTransform<unsigned int,struct CryptoPP::EnumToType<enum CryptoPP::ByteOrder,0>,64,16,class CryptoPP::Weak1::MD5,0,0>::Init(void)" (?Init@?$IteratedHashWithStaticTransform@IU?$EnumToType@W4ByteOrder@CryptoPP@@$0A@@CryptoPP@@$0EA@$0BA@VMD5@Weak1@2@$0A@$0A@@CryptoPP@@MEAAXXZ)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\Hashing.cpp.obj : error LNK2019: unresolved external symbol "public: static void __cdecl CryptoPP::Weak1::MD5::Transform(unsigned int *,unsigned int const *)" (?Transform@MD5@Weak1@CryptoPP@@SAXPEAIPEBI@Z) referenced in function "protected: virtual void __cdecl CryptoPP::IteratedHashWithStaticTransform<unsigned int,struct CryptoPP::EnumToType<enum CryptoPP::ByteOrder,0>,64,16,class CryptoPP::Weak1::MD5,0,0>::HashEndianCorrectedBlock(unsigned int const *)" (?HashEndianCorrectedBlock@?$IteratedHashWithStaticTransform@IU?$EnumToType@W4ByteOrder@CryptoPP@@$0A@@CryptoPP@@$0EA@$0BA@VMD5@Weak1@2@$0A@$0A@@CryptoPP@@MEAAXPEBI@Z)
C:\Users\myuser\Documents\myexec\out\build\x64-Debug (default)\myexec.exe : fatal error LNK1120: 2 unresolved externals

回答1:

C:\Users\myuser\cryptopp\Win32\DLL_Output\Debug\cryptopp.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'

Your problem seems to be coming from here. you're running on a higher architecture of OS (x64) while linking to a crypto library designed for a lower OS architecture (x86) which is a 32 bit. consider linking to a cyrpto library designed for x64

回答2:

OK I have managed to build a minimum reproducible example that works.

Download https://github.com/weidai11/cryptopp and extract to E:\__experiments\cryptopp\cryptopp-master

Open cryptest.sln in Visual Studio, select x64 configuration and build.

Under directory E:__experiments\cryptopp\testprog:

build\
src\main.cpp
CMakeLists.txt

CMakeLists.txt:

cmake_minimum_required (VERSION 3.15)

# this enables the MSVC_RUNTIME_LIBRARY property for slightly older CMake versions
cmake_policy(SET CMP0091 NEW)

project ("MD5test")

add_executable(MD5test "src/main.cpp")

# this is equivalent to setting C/C++ -> Code Generation -> Runtime Library in the Visual Studio project property pages
set_property(TARGET MD5test 
             PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")

find_library(CRYPTOPP_LIB cryptlib.lib HINTS E:/__experiments/cryptopp/cryptopp-master/x64/Output/*)

target_link_libraries(MD5test PUBLIC "${CRYPTOPP_LIB}")

target_include_directories(MD5test PUBLIC "E:/__experiments/cryptopp/cryptopp-master")

src\main.cpp:

#define CRYPTOPP_ENABLE_NAMESPACE_WEAK 1 // Needed to use MD5 in Crypto++

#include <cryptlib.h>
#include <md5.h>
#include <string>
#include <iostream>

#define byte unsigned char

using std::string;

string get_hash(const string& str)
{
    string digest;
    CryptoPP::Weak::MD5 hash;

    hash.Update((const byte*)(str.data()), str.size());
    digest.resize(hash.DIGESTSIZE);
    hash.Final((byte*)&digest[0]);

    return digest;
}


int main (int argc, char** argv)
{
    string hash = get_hash("coconuts");
    std::cout << hash << std::endl;
    return 0;

Open a "Developer command prompt for VS2019" and navigate to the testprog dir, then enter:

del build
mkdir build
cd build
cmake  -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON ..
cmake --build .

Debug\MD5test.exe

Alternatively write a batch file in the test root, do_build.bat, so you can use a plain command prompt window:

call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\VsDevCmd.bat"
cd .
del /F /Q build
rd /S /Q build
mkdir build
cd build
cmake  -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON ..
cmake --build .
cd ..

来源：https://stackoverflow.com/questions/64334300/linking-crypto-fails-when-building-a-c-project-using-cmake

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