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

Tue Feb 7 03:37:40 EST 2017

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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