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FindZLIB: fix CMAKE_FIND_LIBRARY_PREFIXES being unset when it was empty

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CMAKE_FIND_LIBRARY_PREFIXES and CMAKE_FIND_LIBRARY_SUFFIXES have
different behavior when undefined and when defined but empty:
Empty means to use an empty prefix/suffix while undefined means to
use a hardcoded default for the platform we are running on.

Unfortunately, set(a ${b}) will undefine a when b is empty,
meaning that when targeting a platform where either of these variables
is empty (e.g. Windows where CMAKE_FIND_LIBRARY_PREFIXES is empty)
the unpatched FindZLIB code ends up unsetting that variable, causing
all subsequent find_library calls to use the hardcoded default
for the runtime platform (e.g. "lib" for CMAKE_FIND_LIBRARY_PREFIXES
on Linux).

On the other hand, set(a "${b}") will always define a to be empty but
defined so we have to do this dance to fully preserve the state of these
variables.
This commit is contained in:
Daniel Scharrer
2022-09-05 23:42:28 +02:00
committed by Brad King
parent 6dd6f91117
commit 67b6f1a09b
1 changed files with 20 additions and 4 deletions
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24
Modules/FindZLIB.cmake
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@@ -92,8 +92,16 @@ endforeach()
# Allow ZLIB_LIBRARY to be set manually, as the location of the zlib library
if(NOT ZLIB_LIBRARY)
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES ${CMAKE_FIND_LIBRARY_PREFIXES})
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
if(DEFINED CMAKE_FIND_LIBRARY_PREFIXES)
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES "${CMAKE_FIND_LIBRARY_PREFIXES}")
else()
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES)
endif()
if(DEFINED CMAKE_FIND_LIBRARY_SUFFIXES)
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES "${CMAKE_FIND_LIBRARY_SUFFIXES}")
else()
set(_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES)
endif()
# Prefix/suffix of the win32/Makefile.gcc build
if(WIN32)
list(APPEND CMAKE_FIND_LIBRARY_PREFIXES "" "lib")
@@ -114,8 +122,16 @@ if(NOT ZLIB_LIBRARY)
endforeach()
# Restore the original find library ordering
set(CMAKE_FIND_LIBRARY_SUFFIXES ${_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES})
set(CMAKE_FIND_LIBRARY_PREFIXES ${_zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES})
if(DEFINED _zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES)
set(CMAKE_FIND_LIBRARY_SUFFIXES "${_zlib_ORIG_CMAKE_FIND_LIBRARY_SUFFIXES}")
else()
set(CMAKE_FIND_LIBRARY_SUFFIXES)
endif()
if(DEFINED _zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES)
set(CMAKE_FIND_LIBRARY_PREFIXES "${_zlib_ORIG_CMAKE_FIND_LIBRARY_PREFIXES}")
else()
set(CMAKE_FIND_LIBRARY_PREFIXES)
endif()
include(${CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
select_library_configurations(ZLIB)