I am trying to configure the last version of clang (6.0) to use the arm-none-eabi linker instead of the ld.lld but clang is always ignoring everything and keep asking for the ld.lld one. I am trying to build for cortex-m3 (lpx1769 board). How do I force clang to use the linker I want.
-fuse-ld=ld is also not working, so does clang no longer allow the use of any other linker?
So the answer was to use the flag:
-fuse-ld=path/to/linker-to-be-used
Remember that if you passing this flag to clang it will cause a warning that clang will not use this flag (only the linker stage will do). Thus if you compiling with -Werror, the warning will be turned into an error.
Moreover, because you are cross-compiling probably you will need to let the linker know where to find the target-specific libraries needed using the -L option. See this for more info:
https://clang.llvm.org/docs/CrossCompilation.html
Related
I have a cc_library (tbb) that requires the compiler flag -mwaitpkg on some compilers (Clang) to compile successfully. At the same time, there are older versions of GCC (4.9) that do not know this flag, and therefore the compilation via GCC 4.9 leads to an error:
gcc: error: unrecognized command line option '-mwaitpkg'
In a more advanced Bazel setup, I guess one would work around this using hermetic toolchains. This way every toolchain could provide its own set of compiler flags. Nevertheless, I do not want to enforce any specific toolchain and I am not sure if this is the right way to go (move copts to toolchain?).
Also introducing a config would be a way to solve this problem. E.g. bazel build --config=waitpkg //.... But this would require that a user is aware of this config and also knows the details of using waitpkg.
What is a proper "Bazel-way" to handle different compiler flags for different compilers?
The flag '-mwaitpkg' is supported by GCC version 9.3, Clang* 12, and newer versions of those tools.
If you build Bazel with earlier versions of GCC, you should remove the flag otherwise it gives compilation errors.
I have a code running on a PowerPC e500v2 embedded Linux and I want to measure its performance since it is running in an infinite loop. I tried gcc's gprof which was simply by adding -pg option to gcc. When I run the binary on the target device I get this:
./main: /lib/libc.so.6: version GLIBC_2.16 not found (required by ./main)
I am using ELDK 5.6 toolchain with the default CFLAGS and LDFLAGS and these flags: -Wall -lrt -pthread -D_GNU_SOURCE nothing else. Some article suggested defining FORTIFY_SOURCE along with an optimization level but it did not work. I searched for some gcc's feature test macros and tried defining some GLIBC 2.16 specific macros but it did not work.
I faced similar issue with GLIBC 2.17 when I used some structures and functions from <sched.h>, adding _GNU_SOURCE resolved it. Any idea on how to resolve it?
When I run the binary on the target device I get this
Your tool chain targets a version of GLIBC that is newer than what is installed on the target.
This doesn't bite you in non-pg compiles only by accident. An "innocent" change to your source can cause the same problem.
You need to upgrade your target to the version of GLIBC which your toolchain actually builds for.
My cmake project shall compile c++14 code. It also uses the CMakeLists.txts included from its external libraries (which are git submodules in my project). The build fails on macOS Sierra (cmake 3.6.2) because the default STL of clang is old and doesn't handle c++11. As far as I understand, there are two STLs shipped with clang: libstdc++ (from gcc) (default) or libc++. So if I add the -stdlib=libc++ option to cmake, the source compiles:
add_compile_options( "$<$<COMPILE_LANGUAGE:CXX>:-std=c++14>" )
add_compile_options( "$<$<COMPILE_LANGUAGE:CXX>:-stdlib=libc++>" )
But then it fails at link time because it tries to use libstdc++ for linking. How do I specify in cmake that the new STL libc++ shall be used for the whole build process?
PS: What is the rationale behind clang using the gcc STL by default if it is too old? Could I permanently specify which STL it shall use? Or am I doing something completely wrong (could some of my subprojects silently force gcc?)?
You should rely on CMake to handle compile options. Just specify the wanted standard version:
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
target_compile_features can also be used to require particular features of the standard (and implicitly ask CMake to set the adequate configuration). More information here.
EDIT
You figured out the solution, you also had to remove the following line in the CMakeLists of Ogred3D:
set(CMAKE_OSX_DEPLOYMENT_TARGET 10.7)
Removing it prevented CMake to add the flag mmacosx-version-min=10.7 causing the error.
I suppose, you also need to pass that flang to the linker in the clang case:
link_libraries("-stdlib=libc++")
I have an powerpc cross compiled gcc tool chain of version 3.4.3
I am getting certain error for options which are not supported by this compiler like (unrecognized command line option "-Wno-pointer-sign")
Is there a way i can print all supported compiler option for this gcc version. I dont have source code for this.
You can use gcc --help=warnings to get the full list of supported -Wsomething options. Regarding the rest, there're gcc --help=common, gcc --help=params etc, check gcc --help output
I am trying to build a project on Mac OS X using clang and it fails on linking step with ld: unknown option: --no-undefined, which is meant to built with gcc.
What's the clang equivalent for this option? (Please, don't advise to use gcc instead of clang.)
Also, a more generic question, is there any resource where one can find some kind of a "mapping" between gcc and clang (linker) options differences?
Thank you.
OS X uses a different linker. As #rubenvb points out, it's probably the one from Apple's binutils. If you run man ld, and search for "undefined", you will find this option:
-undefined treatment
Specifies how undefined symbols are to be treated. Options are: error, warning, suppress, or dynamic_lookup. The default is error.
So, replace -Wl,--no-undefined with -Wl,-undefined,error. Also, use the Force, Luke.