link to zlib::zlib

cache_dir may be undefined

CMakeLists.txt

@@ -334,8 +334,7 @@ target_include_directories(cifpp
 	"${BOOST_REGEX_INCLUDE_DIR}"
 )
 
-target_link_libraries(cifpp PUBLIC Threads::Threads  ${CIFPP_REQUIRED_LIBRARIES})
-target_link_libraries(cifpp PRIVATE $<BUILD_INTERFACE:ZLIB::ZLIB>)
+target_link_libraries(cifpp PUBLIC Threads::Threads ZLIB::ZLIB ${CIFPP_REQUIRED_LIBRARIES})
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
 	target_link_options(cifpp PRIVATE -undefined dynamic_lookup)

README.md

@@ -83,8 +83,8 @@ Other requirements are:
   library to do amongst others matrix calculations. This usually can be
   installed using your package manager, in Debian/Ubuntu it is called
   `libeigen3-dev`
-- zlib, the development version of this library. On Debian/Ubuntu this
-  is the package `zlib1g-dev`.
+- [zlib](https://github.com/madler/zlib), the development version of this
+  library. On Debian/Ubuntu this is the package `zlib1g-dev`.
 - [boost](https://www.boost.org).
 
 The Boost libraries are only needed in case you want to build the test

src/compound.cpp

@@ -591,8 +591,10 @@ void compound_factory::report_missing_compound(const std::string &compound_id)
 		
 		cif::list_data_directories(std::clog);
 
-		std::clog << "\n(Note that you can add a directory to the search paths by setting the LIBCIFPP_DATA_DIR environmental variable)\n\n"
-				  << "On Linux an optional cron script might have been installed that automatically updates\n"
+		std::clog << "\n(Note that you can add a directory to the search paths by setting the LIBCIFPP_DATA_DIR environmental variable)\n\n";
+
+#if defined(CACHE_DIR)		
+		std::clog << "On Linux an optional cron script might have been installed that automatically updates\n"
 				  << "components.cif and mmCIF dictionary files. This script only works when the file\n"
 				  << "libcifpp.conf contains an uncommented line with the text:\n\n"
 				  << "update=true\n\n"
@@ -601,6 +603,7 @@ void compound_factory::report_missing_compound(const std::string &compound_id)
 				  << "curl -o " << CACHE_DIR << "/components.cif https://ftp.wwpdb.org/pub/pdb/data/monomers/components.cif.gz\n" 
 				  << "curl -o " << CACHE_DIR << "/mmcif_pdbx.dic https://mmcif.wwpdb.org/dictionaries/ascii/mmcif_pdbx_v50.dic.gz\n" 
 				  << "curl -o " << CACHE_DIR << "/mmcif_ma.dic https://github.com/ihmwg/ModelCIF/raw/master/dist/mmcif_ma.dic\n\n";
+#endif
 
 		if (m_impl)
 		{