I am compiling clang 11.1.0 from source and I want it to be configured to use an alternative sysroot by default, such that when I compile a program using clang it will take the system headers and libraries from this alternative sysroot path by default.
For example suppose I have /path/to/my/toolchain as my sysroot.
When I configured and built gcc I used the options --with-sysroot=/path/to/my/toolchain and --with-native-headers=/path/to/my/toolchain. Now every time I compile a program with gcc it takes the system headers/libraries automatically from /path/to/my/toolchain.
I want to do the same with clang. The only way I could get it working so far is to have the option -isysroot /path/to/my/toolchain every time I compile a program. Is there a way to specify the sysroot path when compiling clang so that it becomes the default sysroot when running clang?
Use DEFAULT_SYSROOT cmake variable. E.g. cmake -DDEFAULT_SYSROOT=<your_sysroot_path>
Related
I have spent a few hours trying to get the built-from-sources version of clang (v15) to work with the memtag sanitiser. For those of you who don't know what that is, it is simply a version of the address sanitiser that leverages the Memory Tagging features of ARM.
Anyway, while I can use it normally with the repository version of clang (v10), using the version built from sources just does not work.
Here is the command I use for both: clang main.c -S -march=armv8+memtag -fsanitize=memtag with clang which is either the repository-version or the built-from-sources version. Although the former works seamlessly, the latter does not.
I've tried to built llvm with different parameters, but none seemed to have done the trick. Here's my current building configuration:
cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;lld;lldb;openmp;polly;pstl;compiler-rt" -DLLVM_TARGETS_TO_BUILD="AArch64" ../llvm
I wonder if there is some parameter I have to specify to build clang with this sanitiser enabled.
PS: using the -fsanitize=memtag flag does not give any error: with the built version of clang it simply does not insert the instrumentation code.
If anybody is able to give me some insight I would really appreciate it. Thanks ;)
I want to create a software-generated control flow diagram for this code using LLVM CFG https://github.com/inmcm/Simon_Speck_Ciphers/blob/master/C/speck.c
But when I followed the instructions given on the LLVM webpage (https://www.programmersought.com/article/61364910575/), and typed the following command: clang -S -emit-llvm simon.c -o g.ll
Terminal shows this error message:
clang: error: -emit-llvm cannot be used when linking
I am new to this tool and Linux, can someone please help?
I was able to generate the llvm IR and the CFG dot files for the above mentioned speck.c file. The message cannot be used when linking appears only when you haven't passed any special flags for output like -S, -c, etc. so I'm guessing you have made some typo in the command.
You can try using clang -save-temps speck.c command, which would generate the bitcode (.bc) file for the LLVM IR, which can be used in any place where the .ll file is used.
Trying to convert a large gcc/makefile project into clang. Got it roughly working for x86, but now I'm trying to get cross compilation working.
The way it currently works is that we use Linaro's 7.1.1 arm compiler alongside its companion sysroot directory for base libraries/headers. I installed clang-6.0 and then the base clang(not sure if that mattered).
I used some commands I found to redirect clang to clang-6.0 and when I execute 'clang -v' and got
clang version 6.0.0-1ubuntu2~16.04.1 (tags/RELEASE_600/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
....
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/9
....
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.5.0
....
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;#m64
Selected multilib: .;#m64
It does not find the current compiler we use which is at
/usr/local/gcc-linaro-7.1.1-2017.08-i686_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-g++(also a directory for *x86_64*)
I only found references to setting --sysroot, but not to a specific compiler. Definitely still lost about the relationship between clang+llvm+other compilers. I even saw somewhere saying I needed to compile llvm before I could use it?
I very roughly made changes in our make files to get the following output, basically all I had to add was '-target arm-linux-gnueabuhf' and reordered the mcpu/mfloat/marm/march so they came after -target in case it mattered
clang --sysroot=/usr/local/sysroot-glibc-linaro-2.25-2017.08-arm-linux-gnueabihf -c -std=c++0x
-g -DDEBUG_ON -target arm-linux-gnueabihf -mcpu=cortex-a7 -mfloat-abi=hard -marm -march=armv7ve
-Wall -fexceptions -fdiagnostics-show-option -Werror .... -I/usr/local/gcc-linaro-7.1.1-2017.08-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/include .... and many more
I think the problem probably lies with the change I made which is the actual 'clang' call that replaced
/usr/local/gcc-linaro-7.1.1-2017.08-i686_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-g++ ....
End up with
fatal error: 'cstdarg' file not found
#include <cstdarg>
As said before I can already cross-compile with gcc, so I've already come across issues with std libraries that require 'build-essentials', 'g++-multilibs', etc. So they're already installed.
Looked and really haven't found anything too useful to me, I'm on linux mint 18.3 and the closest things I found were issues people had on mac and windows.
So I came across some posts mentioning setting --gcc-toolchain=/your/choice/of/cross/compiler but they also mention it not working. I discovered that if you combine this with the installation of llvm-6.0-dev(or maybe llvm-6.0-tools, tools installed dev so not 100%) it at least worked for me.
Any compiler clang or gcc needs to know where a header file is defined. The standard headers, standard libraries, c-runtime, and libc are all packaged together for each target e.g., arm64, x86 in a directory called 'sysroot'. When we compile a program we need to pass the path to sysroot for a compiler to know where to look for standard headers during compilation, and where to look for common libraries (libc, libstdc++ etc) during linkage.
Normally when we compile a program for the same machine the compiler uses the standard headers available in '/usr/include' and libraries from '/usr/lib'. When cross-compiling programs we should supply the sysroot as compiler flag. e.g. gcc --sysroot="/path/to/arm64/sysroot/usr" test.cpp. Same for clang. Most often pre-packaged cross compilers come with a script/binary that has 'sysroot' path embedded into it. e.g., aarch64-linux-gnu-gcc (https://packages.ubuntu.com/xenial/devel/gcc-aarch64-linux-gnu).
... the closest things I found were issues people had on mac and windows.
On mac the clang compiler will have the similar configuration as linux. So the details you found there should be totally applicable to yours.
More details on sysroot and cross-compilation:
https://elinux.org/images/1/15/Anatomy_of_Cross-Compilation_Toolchains.pdf
I am trying to use LLVM to do some static analysis on some programs. Specifically, I am targeting Linux kernel source code. However, in the first step of translating the source code of one single file in Linux kernel to LLVM bitcode file, I got stuck.
The command I am using is:
clang -Iinclude/path -c -emit-llvm one_single_file_in_linux_kernel \
-o bitcode_file.bc
The search path for clang is correct, but there are other errors, such as __always_inline not found. I think there should be some other flags I should use, but I don't know.
Has anyone have encountered this problem?
When compiling projects that make use of libraries installed via MacPorts (boost, opencv, etc) I need to pass clang the library and include file locations via the -I and -L arguments.
Is there any "official" way to direct the Apple native clang look in these locations by default.
I guess I could just make a bash script with something to the effect of
clang -I/opt/local/include -L/opt/local/lib %#
and call that instead of the compiler, but is there a cleaner way to point clang to these locations automatically?
I am not looking for an Xcode based fix, instead I would like to be able to compile from the command line without having to manually type the above arguments in each time.
Any suggestions?
I had a similar question answered on the MacPorts mailing list[0].
Export these environment variables.
export CPPFLAGS='-isystem/opt/local/include'
export LDFLAGS='-L/opt/local/lib'
P.S. Hope you've not been waiting this long for an answer :)
[0] https://lists.macports.org/pipermail/macports-users/2017-July/043562.html