error LNK2019: unresolved external symbol referenced when compile HTTPD - c++

Question

I'm compiling HTTPD 2.4.48 along with Lua, Zlib, cURL, jansson and OpenSSL.
Here is the list of files and software I use:
httpd-2.4.48
apr-1.7.0
apr-util-1.6.1
cURL 7.77.0
expat-2.4.1
jansson 2.13.1
Lua 5.4.3
mod_fcgid 2.3.9
openssl-1.1.1k
pcre-8.44
ZLIB 1.2.11
ActivePerl v5.28.1.2801 (x64)
CMake v3.20.3 (x64)
NASM v2.15.05 (x64)
Gawk v3.1.6-1 (x86)
The whole compile statement I use:
Visual Studio 2015: call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" amd64
*****************
** ZLIB Build **
*****************
cd /D C:\httpd\srclib\zlib\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON ..
nmake
nmake install
****************
** Pcre Build **
****************
cd /D C:\httpd\srclib\pcre\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -DPCRE_BUILD_TESTS=OFF -DPCRE_BUILD_PCRECPP=OFF -DPCRE_BUILD_PCREGREP=OFF -DPCRE_SUPPORT_PCREGREP_JIT=OFF -DPCRE_SUPPORT_UTF=ON -DPCRE_SUPPORT_UNICODE_PROPERTIES=ON -DPCRE_NEWLINE=CRLF -DINSTALL_MSVC_PDB=OFF ..
nmake
nmake install
*****************
** Expat Build **
*****************
cd /D C:\httpd\srclib\expat\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON ..
nmake
nmake install
*******************
** OpenSSL Build **
*******************
cd /D C:\httpd\srclib\openssl
perl Configure VC-WIN64A --release --prefix=\phpStudy\Apache --openssldir=\phpStudy\Apache\conf enable-camellia no-idea no-mdc2 no-ssl2 no-ssl3
nmake
nmake install
***************
** Lua Build **
***************
cd /D C:\httpd\srclib\lua\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release ..
nmake
nmake install
****************
** cURL Build **
****************
cd /D C:\httpd\srclib\curl\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON ..
nmake
nmake install
*******************
** jansson Build **
*******************
cd /D C:\httpd\srclib\jansson\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON ..
nmake
nmake install
***************
** APR Build **
***************
cd /D C:\httpd\srclib\apr\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -DMIN_WINDOWS_VER=0x0600 -DAPR_HAVE_IPV6=ON -DAPR_INSTALL_PRIVATE_H=ON -DAPR_BUILD_TESTAPR=OFF -DINSTALL_PDB=OFF ..
nmake
nmake install
********************
** APR-Util Build **
********************
cd /D C:\httpd\srclib\apr-util\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -DOPENSSL_ROOT_DIR=\phpStudy\Apache -DAPU_HAVE_CRYPTO=ON -DAPR_BUILD_TESTAPR=OFF -DINSTALL_PDB=OFF ..
nmake
nmake install
******************
** Apache Build **
******************
cd /D C:\httpd\bin
cmake -G "NMake Makefiles" -DCMAKE_INSTALL_PREFIX=\phpStudy\Apache -DCMAKE_BUILD_TYPE=Release -DENABLE_MODULES=i -DINSTALL_PDB=OFF ..
nmake
nmake install
Everything worked almost perfectly, however in the last step when I compile HTTPD I got the error:
[ 44%] Linking C shared library mod_md.so
LINK: command "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\amd64\link.exe /nologo #CMakeFiles\mod_md.dir\objects1.rsp /out:mod_md.so /implib:mod_md.lib /pdb:C:\httpd\bin\mod_md.pdb /dll /version:0.0 /base:#C:/httpd/bin/BaseAddr.ref,mod_md.so /machine:x64 /INCREMENTAL:NO \phpStudy\Apache\lib\libssl.lib \phpStudy\Apache\lib\libcrypto.lib \phpStudy\Apache\lib\jansson.lib mod_watchdog.lib libhttpd.lib \phpStudy\Apache\lib\libapr-1.lib \phpStudy\Apache\lib\libaprutil-1.lib \phpStudy\Apache\lib\apr_ldap-1.lib ws2_32.lib mswsock.lib \phpStudy\Apache\lib\pcre.lib ws2_32.lib mswsock.lib kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib oleaut32.lib uuid.lib comdlg32.lib advapi32.lib /MANIFEST /MANIFESTFILE:mod_md.so.manifest" failed (exit code 1120) with the following output:
Creating library mod_md.lib and object mod_md.exp
md_curl.c.obj : error LNK2019: unresolved external symbol curl_global_init referenced in function md_curl_init
md_curl.c.obj : error LNK2019: unresolved external symbol curl_slist_append referenced in function curlify_headers
md_curl.c.obj : error LNK2019: unresolved external symbol curl_slist_free_all referenced in function md_curl_req_cleanup
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_strerror referenced in function md_curl_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_init referenced in function internals_setup
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_setopt referenced in function internals_setup
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_perform referenced in function md_curl_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_cleanup referenced in function md_curl_req_cleanup
md_curl.c.obj : error LNK2019: unresolved external symbol curl_easy_getinfo referenced in function md_curl_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_init referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_add_handlereferenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_remove_handle referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_wait referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_perform referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_cleanup referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_info_read referenced in function md_curl_multi_perform
md_curl.c.obj : error LNK2019: unresolved external symbol curl_multi_strerror referenced in function md_curl_multi_perform
mod_md.so : fatal error LNK1120: 17 unresolved externals
NMAKE : fatal error U1077: '"C:\Program Files\CMake\bin\cmake.exe"' : return code '0xffffffff'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\BIN\amd64\nmake.exe"' : return code '0x2'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\BIN\amd64\nmake.exe"' : return code '0x2'
Stop.
I found out the answer of this question: Visual Studio 2015 curl will not statically link
Change the code of the md_curl.c file to:
#pragma comment(lib, "wldap32.lib" )
#pragma comment(lib, "crypt32.lib" )
#pragma comment(lib, "Ws2_32.lib")
#define CURL_STATICLIB
#include <curl/curl.h>
But this error still occurs.
Where did I go wrong? I'm getting confused because this is the first time I've encountered this error when compiling HTTPD.
Your answer will be very helpful. I would appreciate that!

Answer 1

Whenever you fix issues, start by the first one (cause solving that may remove the remaining), which in you case seems to be:
error LNK2019: unresolved external symbol curl_global_init referenced in function md_curl_init
And it basically is telling us that, the md_curl_init method calls curl_global_init method, but while compile-time declaration was available, the linker-time required definition is missing.
Anyway, to fix this ensure curl is added as a library, I mean, is currently not in your linker command-line (not in what you posted at least).
Edit I will suggest you approaches, for how you can do that.
But first, giving it more time, I see that:
Yes, you already compile curl.
Your "whole compile statement" thing is using C:\httpd\srclib\curl\bin as build-directory for cURL.
Also, you should be able to find curl.lib in C:\httpd\srclib\curl\bin directory (which was used as build-directory).
Approach #1:
Create a root CMakeFiles.txt file and add your other projects with add_subdirectory(...) method.
I recommend this approach, as CMake will handle for you the task of finding curl automatically.
I mean, you just would need to do something like:
target_link_libraries(myTargetThatNeedsCurl
curl
)
Approach #2:
If you don't want to change "whole compile statement" thing, then your only choice may be to place curl.lib somewhere that your other build-script can find it (manually or through some custom install(...) method calls, I leave that to you).
Approach #3:
First, edit httpd project (the C:\httpd\CMakeFiles.txt file), and add add_subdirectory(srclib/curl) somewhere in beginning.
Then, find cURL target's name, like, open the C:\httpd\srclib\curl\CMakeFiles.txt file and see all add_library(...) call's first argument (one of them is what we want).
Finally, edit httpd project again, but now add what you found in step-2 as argument to target_link_libraries(...) method.
Note that Approach #3 is same as #2, but just for cURL (instead of adding all sub-directories).