CMake: Don't use libraries in /usr/local by default on macOS

qmake builds of Qt don't use libraries in /usr/local because the
path is not considered a system path. Only the SDK path should be
used as a source of system libraries.

We should do the same for the CMake builds, which involves a couple of
things.

Tell CMake not to consider /usr/local (and a bunch of other
paths) as system prefix paths.

Disable pkg-config usage which by default is not used in qmake
Windows and macOS builds.

If a user wishes to use libraries located in /usr/local on macOS, they
can explicitly enable the behavior via -DFEATURE_pkg_config=ON.

In addition to enabling pkg-config, that will also disable the system
prefix modification described above.

Implementation notes

To disable pkg-config usage, we set an empty path for
PKG_CONFIG_EXECUTABLE, because there is no other good way. The
downside to this is that a lot of warning messages will be printed
that the pkg-config package can not be found.

The pkg-config feature needs to be computed in QtBuildInternals before
qtbase/src/configure.cmake, because it's too late to do it in that
file where a few qt_find_package calls already exist.
The feature value is also saved to QtBuildInternalsExtra, to make sure
that pkg-config is disabled whenever building another repo.

System prefix adjustment is done by removing paths from
CMAKE_SYSTEM_PREFIX_PATH.
Ideally we would remove also /usr as a path, to match what qmake does,
but that breaks find_program() calls for perl, python, etc.

We have to make sure that qt_find_package does not look in
PATH when looking for packages, which is the default behavior, because
PATH on macOS most likely contains /usr/local.

One last curiosity for future generations is that CMake 3.18+ has
merged a change to prioritise SDK locations over regular /usr/lib.

Fixes: QTBUG-85261
Change-Id: I28fe5bae7997507a83b37b4eb1e0188e64062c57
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
This commit is contained in:
Alexandru Croitor 2020-06-25 18:02:52 +02:00
parent 45c0f45e04
commit f3c7d22dd0
3 changed files with 114 additions and 0 deletions

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@ -5246,6 +5246,12 @@ macro(qt_find_package)
list(APPEND arg_UNPARSED_ARGUMENTS "COMPONENTS;${arg_COMPONENTS}")
endif()
# Don't look for packages in PATH if requested to.
if(QT_NO_USE_FIND_PACKAGE_SYSTEM_ENVIRONMENT_PATH)
set(_qt_find_package_use_system_env_backup "${CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH}")
set(CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH "OFF")
endif()
if(NOT (arg_CONFIG OR arg_NO_MODULE OR arg_MODULE) AND NOT _qt_find_package_skip_find_package)
# Try to find a config package first in quiet mode
set(config_package_arg ${arg_UNPARSED_ARGUMENTS})
@ -5291,6 +5297,14 @@ macro(qt_find_package)
find_package(${arg_UNPARSED_ARGUMENTS})
endif()
if(QT_NO_USE_FIND_PACKAGE_SYSTEM_ENVIRONMENT_PATH)
if("${_qt_find_package_use_system_env_backup}" STREQUAL "")
unset(CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH)
else()
set(CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH "${_qt_find_package_use_system_env_backup}")
endif()
endif()
if(${ARGV0}_FOUND AND arg_PROVIDED_TARGETS AND NOT _qt_find_package_skip_find_package)
# If package was found, associate each target with its package name. This will be used
# later when creating Config files for Qt libraries, to generate correct find_dependency()

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@ -51,6 +51,98 @@ endif()
# build.
include(QtPlatformSupport)
function(qt_build_internals_disable_pkg_config_if_needed)
# pkg-config should not be used by default on Darwin and Windows platforms, as defined in
# the qtbase/configure.json. Unfortunately by the time the feature is evaluated there are
# already a few find_package() calls.
# So we have to duplicate the condition logic here and disable pkg-config for those platforms by
# default.
#
# Note that on macOS, if the pkg-config feature is enabled by the user explicitly, we will also
# tell CMake to consider paths like /usr/local (Homebrew) as system paths when looking for
# packages.
# We have to do that because disabling these paths but keeping pkg-config
# enabled won't enable finding all system libraries via pkg-config alone, many libraries can
# only be found via FooConfig.cmake files which means /usr/local should be in the system prefix
# path.
set(pkg_config_enabled ON)
if(APPLE OR WIN32)
set(pkg_config_enabled OFF)
endif()
if(DEFINED FEATURE_pkg_config)
if(FEATURE_pkg_config)
set(pkg_config_enabled ON)
else()
set(pkg_config_enabled OFF)
endif()
endif()
set(FEATURE_pkg_config "${pkg_config_enabled}" CACHE STRING "Using pkg-config")
if(NOT pkg_config_enabled)
qt_build_internals_disable_pkg_config()
else()
unset(PKG_CONFIG_EXECUTABLE CACHE)
endif()
endfunction()
function(qt_build_internals_disable_pkg_config)
# Disable pkg-config by setting an empty executable path. There's no documented way to
# mark the package as found, but force all pkg_check_modules calls to do nothing.
set(PKG_CONFIG_EXECUTABLE "" CACHE STRING "Disabled pkg-config usage." FORCE)
endfunction()
if(NOT QT_BUILD_INTERNALS_SKIP_PKG_CONFIG_ADJUSTMENT)
qt_build_internals_disable_pkg_config_if_needed()
endif()
macro(qt_build_internals_find_pkg_config)
# Find package config once before any system prefix modifications.
find_package(PkgConfig QUIET)
endmacro()
if(NOT QT_BUILD_INTERNALS_SKIP_FIND_PKG_CONFIG)
qt_build_internals_find_pkg_config()
endif()
function(qt_build_internals_set_up_system_prefixes)
if(APPLE AND NOT FEATURE_pkg_config)
# Remove /usr/local and other paths like that which CMake considers as system prefixes on
# darwin platforms. CMake considers them as system prefixes, but in qmake / Qt land we only
# consider the SDK path as a system prefix.
# 3rd party libraries in these locations should not be picked up when building Qt,
# unless opted-in via the pkg-config feature, which in turn will disable this behavior.
#
# Note that we can't remove /usr as a system prefix path, because many programs won't be
# found then (e.g. perl).
set(QT_CMAKE_SYSTEM_PREFIX_PATH_BACKUP "${CMAKE_SYSTEM_PREFIX_PATH}" PARENT_SCOPE)
set(QT_CMAKE_SYSTEM_FRAMEWORK_PATH_BACKUP "${CMAKE_SYSTEM_FRAMEWORK_PATH}" PARENT_SCOPE)
list(REMOVE_ITEM CMAKE_SYSTEM_PREFIX_PATH
"/usr/local" # Homebrew
"/usr/X11R6"
"/usr/pkg"
"/opt"
"/sw" # Fink
"/opt/local" # MacPorts
)
if(_CMAKE_INSTALL_DIR)
list(REMOVE_ITEM CMAKE_SYSTEM_PREFIX_PATH "${_CMAKE_INSTALL_DIR}")
endif()
list(REMOVE_ITEM CMAKE_SYSTEM_FRAMEWORK_PATH "~/Library/Frameworks")
set(CMAKE_SYSTEM_PREFIX_PATH "${CMAKE_SYSTEM_PREFIX_PATH}" PARENT_SCOPE)
set(CMAKE_SYSTEM_FRAMEWORK_PATH "${CMAKE_SYSTEM_FRAMEWORK_PATH}" PARENT_SCOPE)
# Also tell qt_find_package() not to use PATH when looking for packages.
# We can't simply set CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH to OFF because that will break
# find_program(), and for instance ccache won't be found.
# That's why we set a different variable which is used by qt_find_package.
set(QT_NO_USE_FIND_PACKAGE_SYSTEM_ENVIRONMENT_PATH "ON" PARENT_SCOPE)
endif()
endfunction()
if(NOT QT_BUILD_INTERNALS_SKIP_SYSTEM_PREFIX_ADJUSTMENT)
qt_build_internals_set_up_system_prefixes()
endif()
macro(qt_build_internals_set_up_private_api)
# Qt specific setup common for all modules:
include(QtSetup)

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@ -444,6 +444,14 @@ endif()\n")
"set(QT_EXTRA_RPATHS \"${QT_EXTRA_RPATHS}\" CACHE STRING \"\")\n")
endif()
# Save pkg-config feature value to be able to query it internally as soon as BuildInternals
# package is loaded. This is to avoid any pkg-config package from being found when
# find_package(Qt6Core) is called in case if the feature was disabled.
string(APPEND QT_EXTRA_BUILD_INTERNALS_VARS "
if(NOT QT_SKIP_BUILD_INTERNALS_PKG_CONFIG_FEATURE)
set(FEATURE_pkg_config \"${FEATURE_pkg_config}\" CACHE STRING \"Using pkg-config\" FORCE)
endif()\n")
# The OpenSSL root dir needs to be saved so that repos other than qtbase (like qtopcua) can
# still successfully find_package(WrapOpenSSL) in the CI.
# qmake saves any additional include paths passed via the configure like '-I/foo'