Chainbuild fails because of unconditional usage of OPENSSL_LIBRARIES

[Vollstrecker]

I did this

I cloned the repo with fetchcontent while building. As the feature is not needed, I did find_package(OpenSSL) before FetchContent_MakeAvailable to set CURL_USE_OPENSSL to off if it's not buildable, and configuring fails.

To reproduce you can put the following CMakeLists.txt in the parent-directory of your source-dir (curl-8_10_1 and master tested) and try to build that one without findable openssl:

project(test)
find_package(OpenSSL)
set (CURL_USE_OPENSSL OFF CACHE BOOL "")
#unset (OPENSSL_LIBRARIES)
add_subdirectory(curl)

With the commented line your'll get:

-- Looking for stddef.h - found
-- Check size of size_t
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
OPENSSL_CRYPTO_LIBRARY
    linked by target "cmTC_dee16" in directory /home/werner/Devel/Build/curl/CMakeFiles/CMakeScratch/TryCompile-KljE6a
OPENSSL_SSL_LIBRARY
    linked by target "cmTC_dee16" in directory /home/werner/Devel/Build/curl/CMakeFiles/CMakeScratch/TryCompile-KljE6a

CMake Error at /usr/share/cmake-3.30/Modules/CheckTypeSize.cmake:147 (try_compile):
  Failed to generate test project build system.
Call Stack (most recent call first):
  /usr/share/cmake-3.30/Modules/CheckTypeSize.cmake:272 (__check_type_size_impl)
  curl/CMakeLists.txt:1429 (check_type_size)

If you remove the "#" all works fine.

I identified this line to add the libs without any checks. I don't know any of that ldap-related stuff, so I can't just fix this myself.

I expected the following

A clean running config stage

curl/libcurl version

master

operating system

Debian testing

[vszakats]

Thanks for pointing to the offending line. I'm not familiar with OpenLDAP, but if it has a hard requirement on OpenSSL, maybe this fix can work:

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -954,7 +954,7 @@ if(NOT CURL_DISABLE_LDAP)
   set(CMAKE_LBER_LIB "lber" CACHE STRING "Name or full path to lber library")
 
   # Now that we know, we are not using Windows LDAP...
-  if(NOT USE_WIN32_LDAP)
+  if(NOT USE_WIN32_LDAP AND USE_OPENSSL)
     # Check for LDAP
     set(CMAKE_REQUIRED_LIBRARIES ${OPENSSL_LIBRARIES})
     check_library_exists("${CMAKE_LDAP_LIB}" "ldap_init" "" HAVE_LIBLDAP)

And/or -DCURL_DISABLE_LDAP=ON as a workaround.

edit: I'm fairly sure this is more complicated depending on CURL_DISABLE_LDAPS, LDAP capabilities and probably a bunch of other stuff, so I'm hiding this post.

edit2: Though the workaround should work fine, unless wishing to also use OpenLDAP at the same time.