[cmake] Use find_package to discover zlib

[v.g.vassilev]

Summary

This allows us to use standard cmake utilities to point to non-system zlib locations.

[beanz]

interpreter/CMakeLists.txt

27 ↗

(On Diff #119321)

This shouldn't be here.

interpreter/llvm/src/lib/Support/CMakeLists.txt

25 ↗

(On Diff #119321)

The correct variable to use here is ZLIB_LIBRARIES. While ZLIB_LIBRARY probably works in most cases, it is an implementation detail of the FindZLIB CMake package.

[v.g.vassilev]

Address comments.

interpreter/CMakeLists.txt

27 ↗

(On Diff #119321)

Oops ;)

[beanz]

LGTM

[v.g.vassilev]

Landed in r316025.

[v.g.vassilev]

Reverted in r316029 because the bots got angry at me:

CMake Error at /usr/local/share/cmake-3.7/Modules/FindPackageHandleStandardArgs.cmake:138 (message):
  Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
Call Stack (most recent call first):
  /usr/local/share/cmake-3.7/Modules/FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
  /usr/local/share/cmake-3.7/Modules/FindZLIB.cmake:114 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  cmake/config-ix.cmake:135 (find_package)
  CMakeLists.txt:585 (include)

@beanz, do you have an idea what went wrong?

[v.g.vassilev]

I assume this would fix it:

find_package(ZLIB)
if (ZLIB_FOUND)
  set(HAVE_LIBZ 1)
else()
  check_library_exists(z compress2 "" HAVE_LIBZ)
  if(HAVE_LIBZ)
     set(ZLIB_LIBRARIES z)
  endif()
endif()

The question is whether that's the right thing to do.

[v.g.vassilev]

Revised patch landed in r316150.

[v.g.vassilev]

Reverted in r316153...

cmake/config-ix.cmake

 # like strlen, leading to false positives.
 if( NOT PURE_WINDOWS AND NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
   if (LLVM_ENABLE_ZLIB)
-    check_library_exists(z compress2 "" HAVE_LIBZ)
+    find_package(ZLIB REQUIRED)
+    if (ZLIB_FOUND)
+      set(HAVE_LIBZ 1)
+    endif()
   else()
     set(HAVE_LIBZ 0)
   endif()

lib/Support/CMakeLists.txt

   endif()
   set(system_libs ${system_libs} ${LLVM_PTHREAD_LIB})
   if ( LLVM_ENABLE_ZLIB AND HAVE_LIBZ )
-    set(system_libs ${system_libs} z)
+    set(system_libs ${system_libs} ${ZLIB_LIBRARIES})
   endif()
   if( UNIX AND NOT (BEOS OR HAIKU) )
     set(system_libs ${system_libs} m)