[CMake] RPATH cross-compile issue with CHECK_*_EXISTS

Tue Feb 7 04:40:26 EST 2017

The PR Is closed pending me writing a test-case, but I just now
updated to the my latest version and rebased on top of master:

https://gitlab.kitware.com/mingwandroid/cmake/commit/b937ff949d8fdaab7d8b812d503f67f8cef69532

Cheers.

On Tue, Feb 7, 2017 at 8:37 AM,  <joerg.krause at embedded.rocks> wrote:
> Hi Ray,
>
> Am 2017-02-07 02:46, schrieb Ray Donnelly:
>>
>> I have a PR that asks the linker (via the compiler) what its implicit
>> search directories are instead.
>>
>> It is the right way to do it IMHO, but I need to find time to finish
>> it unfortunately.
>
>
> Do you have a link to the PR?
>
>> On Feb 6, 2017 11:16 PM, "Jörg Krause" <joerg.krause at embedded.rocks>
>> wrote:
>>
>>> On Mon, 2017-02-06 at 22:22 +0100, Jörg Krause wrote:
>>>>
>>>> Hi,
>>>>
>>>> On Sun, 2017-02-05 at 23:03 +0100, Jörg Krause wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> when using CHECK_{SYMBOL,FUNCTION}_EXISTS in a cross-compilation
>>>>> environment, CMake passes the host rpath to the linker:
>>>>>
>>>>> """ CMakeOutput.log
>>>>>
>>>>> /home/joerg/host/usr/bin/i586-linux-gcc
>>>>> --sysroot=/home/joerg/host/usr/i586-buildroot-linux-musl/sysroot
>>>>> -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
>>>>> -Os -
>>>>> DNDEBUG CMakeFiles/cmTC_cb8f6.dir/CheckSymbolExists.c.o -o
>>>>> cmTC_cb8f6 -Wl,-rpath,/usr/lib32 -rdynamic
>>>>> /home/joerg/host/usr/i586-
>>>>> buildroot-linux-musl/sysroot/usr/lib32/libmbedtls.so
>>>>> /home/joerg/host/usr/i586-buildroot-linux-
>>>>> musl/sysroot/usr/lib32/libmbedx509.so /home/joerg/host/usr/i586-
>>>>> buildroot-linux-musl/sysroot/usr/lib32/libmbedcrypto.so
>>>>>
>>>>> """
>>>>>
>>>>> This leads to a linker error if mbedtls is linked with zlib, as
>>>
>>> the
>>>>>
>>>>> linker tries to link with the host zlib and does not find the
>>>
>>> host
>>>>>
>>>>> libc:
>>>>>
>>>>> """ CMakeError.txt
>>>>>
>>>>> /home/joerg/host/usr/i586-buildroot-linux-musl/bin/ld: warning:
>>>>> libc.so.6, needed by /usr/lib32/libz.so.1, not found (try using
>>>>> -rpath
>>>>> or -rpath-link)
>>>>> /usr/lib32/libz.so.1: undefined reference to `strcpy at GLIBC_2.0'
>>>>> /usr/lib32/libz.so.1: undefined reference to `free at GLIBC_2.0'
>>>>> /usr/lib32/libz.so.1: undefined reference to `fseeko64 at GLIBC_2.1
>>>>> [..]
>>>>>
>>>>> """
>>>>>
>>>>> I did not find any solution which allows me to remove the rpath
>>>>> from
>>>>> the check. Setting CMAKE_SKIP_RPATH does not change the build
>>>>> behaviour of the check_symbol_exists macro.
>>>>>
>>>>> From my understanding, the rpath flag should not be used when
>>>
>>> the
>>>>>
>>>>> sysroot flag is passed to the linker, right?
>>>>>
>>>>> For reference, I added a minimal example which uses Buildroot
>>>
>>> for
>>>>>
>>>>> cross-compilation.
>>>>>
>>>>> """ CMakeLists.txt
>>>>>
>>>>> cmake_minimum_required(VERSION 2.8.12)
>>>>>
>>>>> project(test)
>>>>>
>>>>> list(APPEND CMAKE_MODULE_PATH
>>>
>>> "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
>>>>>
>>>>>
>>>>> find_package(MbedTLS)
>>>>> if(MBEDTLS_FOUND)
>>>>> message(STATUS "Using mbedTLS")
>>>>> endif()
>>>>>
>>>>> """
>>>>>
>>>>> """ FindMbedTLS.cmake
>>>>>
>>>>> include(CheckSymbolExists)
>>>>>
>>>>> find_path(MBEDTLS_INCLUDE_DIRS
>>>>> NAMES mbedtls/ssl.h
>>>>> PATH_SUFFIXES include
>>>>> )
>>>>>
>>>>> find_library(MBEDTLS_LIBRARY NAMES mbedtls)
>>>>> find_library(MBEDX509_LIBRARY NAMES mbedx509)
>>>>> find_library(MBEDCRYPTO_LIBRARY NAMES mbedcrypto)
>>>>>
>>>>> if(MBEDTLS_LIBRARY AND MBEDX509_LIBRARY AND MBEDCRYPTO_LIBRARY)
>>>>> set(CMAKE_REQUIRED_INCLUDES ${MBEDTLS_INCLUDE_DIRS})
>>>>> set(CMAKE_REQUIRED_LIBRARIES ${MBEDTLS_LIBRARY}
>>>>> ${MBEDX509_LIBRARY} ${MBEDCRYPTO_LIBRARY})
>>>>> check_symbol_exists(mbedtls_ssl_init "mbedtls/ssl.h"
>>>>> MBEDTLS_V2)
>>>>> endif()
>>>>>
>>>>> """
>>>>>
>>>>> """ toolchainfile.cmake
>>>>>
>>>>> string(REPLACE "/usr/share/buildroot" "" RELOCATED_HOST_DIR
>>>>> ${CMAKE_CURRENT_LIST_DIR})
>>>>>
>>>>> set(CMAKE_SYSTEM_NAME Linux)
>>>>> set(CMAKE_SYSTEM_PROCESSOR i586)
>>>>>
>>>>> set(CMAKE_C_FLAGS_DEBUG "" CACHE STRING "Debug CFLAGS")
>>>>> set(CMAKE_CXX_FLAGS_DEBUG "" CACHE STRING "Debug CXXFLAGS")
>>>>> set(CMAKE_C_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release
>>>>> CFLAGS")
>>>>> set(CMAKE_CXX_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release
>>>>> CXXFLAGS")
>>>>>
>>>>> # Build type from the Buildroot configuration
>>>>> set(CMAKE_BUILD_TYPE Release CACHE STRING "Buildroot build
>>>>> configuration")
>>>>>
>>>>> # Buildroot defaults flags.
>>>>> set(CMAKE_C_FLAGS "-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>>>>> -D_FILE_OFFSET_BITS=64 -Os" CACHE STRING "Buildroot CFLAGS")
>>>>> set(CMAKE_CXX_FLAGS "-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>>>>> -D_FILE_OFFSET_BITS=64 -Os" CACHE STRING "Buildroot CXXFLAGS")
>>>>> set(CMAKE_EXE_LINKER_FLAGS "" CACHE STRING "Buildroot LDFLAGS
>>>
>>> for
>>>>>
>>>>> executables")
>>>>>
>>>>> set(CMAKE_INSTALL_SO_NO_EXE 0)
>>>>>
>>>>> set(CMAKE_PROGRAM_PATH "${RELOCATED_HOST_DIR}/usr/bin")
>>>>> set(CMAKE_SYSROOT
>>>
>>> "${RELOCATED_HOST_DIR}/usr/i586-buildroot-linux-
>>>>>
>>>>> musl/sysroot")
>>>>> set(CMAKE_FIND_ROOT_PATH
>>>
>>> "${RELOCATED_HOST_DIR}/usr/i586-buildroot-
>>>>>
>>>>> linux-musl/sysroot")
>>>>> set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
>>>>> set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
>>>>> set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
>>>>> set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
>>>>> set(ENV{PKG_CONFIG_SYSROOT_DIR} "${RELOCATED_HOST_DIR}/usr/i586-
>>>>> buildroot-linux-musl/sysroot")
>>>>>
>>>>> # This toolchain file can be used both inside and outside
>>>>> Buildroot.
>>>>> set(CMAKE_C_COMPILER "${RELOCATED_HOST_DIR}/usr/bin/i586-linux-
>>>>> gcc")
>>>>> set(CMAKE_CXX_COMPILER
>>>
>>> "${RELOCATED_HOST_DIR}/usr/bin/i586-linux-
>>>>>
>>>>> g++")
>>>>>
>>>>> """
>>>>>
>>>>> What do I miss?
>>>>
>>>>
>>>> Note, that this project was build using CMake 3.7.2 on Debian.
>>>
>>> When
>>>>
>>>> using CMake 3.6.3, CMake does correctly not add rpath to the
>>>
>>> cross-
>>>>
>>>> linker and the check_symbol_exists() succeeds.
>>>
>>>
>>> I did a git bisect. The behaviour was introduced in commit
>>> 896ad251de49f167f4ce3cbbcf9a6cce85a16681 [1].
>>>
>>> My suggestion is to set FIND_LIBRARY_USE_LIB32_PATHS and
>>> FIND_LIBRARY_USE_LIB64_PATHS to FALSE when cross-compiling on Linux.
>>>
>>> [1]
>>> https://gitlab.kitware.com/cmake/cmake/commit/896ad251de49f167f4ce3
>>> cbbcf9a6cce85a16681
>>>
>>> Best regards,
>>> Jörg Krause
>>> --
>>>
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>>
>>
>>
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>> ------
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>
>