I have a prepared a minimal Cmake project containing one cpp file which represent the main and one cpp file which represent the shared library, that prints basically hello world.
https://github.com/courteous/wasmELF.git
The target is to compile this miniaml code with emscripten/clang only and produce
1) one WebAssembly (wasm) binary module version 0x1 (MVP)
2) one ELF 64-bit LSB
without clearing the cmake build directory and rebuilding it again.
Currently i can successfully produce them bought by running the commands
emconfigure cmake ../ -DCMAKE_BUILD_TYPE=WASM
make
and
cmake ../ -DCMAKE_BUILD_TYPE=Linux
make
However the problem is that in order to do that i need to compile the first one with Clang the to remove the build and then to do a second compilation with GCC. I would like Emscripten/Clang to produce them bought instead. I do not want to delete the build directory since the compilation times is taking too long. (Well not in this Project but imagine if the project was much larger)
What i see is that emscripten/clang selects always a target "wasm32-unknown-emscripten"
clang++ -target wasm32-unknown-emscripten
and if i understand that correctly the target should change
I do see that the project is producing LLVM IR bitcode since i have send the flag "flto"
i.e.
file TestSharedClass.cpp.o
TestSharedClass.cpp.o: LLVM IR bitcode
and in the CMakeLists.txt
set(CMAKE_CXX_FLAGS "-flto")
x86_64-unknown-linux-gnu is a supported target by emscripten/Clang
~/Projects/emscripten/emsdk/upstream/bin$ ./llc --version
LLVM (http://llvm.org/):
LLVM version 11.0.0git
Optimized build with assertions.
Default target: x86_64-unknown-linux-gnu
Host CPU: haswell
Registered Targets:
wasm32 - WebAssembly 32-bit
wasm64 - WebAssembly 64-bit
x86 - 32-bit X86: Pentium-Pro and above
x86-64 - 64-bit X86: EM64T and AMD64
In cmake i do have
SET(TARGET x86_64-unknown-linux-gnu)
however when i run
emconfigure cmake ../ -DCMAKE_BUILD_TYPE=Linux
make
i get mainTestFile.js and mainTestFile.wasm instead of ELF 64-bitcode.
what i am doing wrong here. How to tell clang to product once ELF and once wasm from the same code run without having to clear the build directory. This should be possible since clang is producing LLVM IR bitcode. Or do i understand that wrong?
https://github.com/emscripten-core/emscripten/issues/10361
OK that seems to not be possible i.e. the reply from the dev on github states that emcc or emmake can not be used with another target other then wasm32-unknown-emscripten.
I'm trying to make custom binaries for initrd for x86 system. I took generic precompiled Debian 7 gcc (version 4.7.2-5) and compiled kernel with it. Next step was to make helloworld program instead of init script in initrd to check my development progress. Helloworld program was also compiled with that gcc. When I tried to start my custom system, kernel started with no problem, but helloworld program encountered some errors:
kernel: init[24879] general protection ip:7fd7271585e0 sp:7fff1ef55070 error:0 in init[7fd727142000+20000]
(numbers are not mine, I took similar string from google). Helloworld program:
#include <stdio.h>
int main(){
printf("Helloworld\r\n");
sleep(9999999);
return 0;
}
Compilation:
gcc -static -o init test.c
Earlier I also had stuck with same problem on ARM system (took generic compiler, compiled kernel and some binaries with it and tried to run, kernel runs, but binary - not). Solved it with complete buildroot system, and took buildroot compiler in next projects.
So my question is: what difference between gcc compiled as part of buildroot and generic precompiled gcc?
I know that buildroot compiler is made in several steps, with differenet libs and so on, is this main difference, platform independence?
I don't need a solution, I can take buildroot anytime. I want to know source of my problem, to avoid such problems in future. Thanks.
UPD: Replaced sleep with while(1); and got same situation. My kernel output:
init[1]: general protection ip: 8053682 sp: bf978294 error: 0 in init[8048000+81000]
printk: 14300820 message suppressed.
and repeating every second.
UPD2: I added vdso32-int80.so (original name, like in kernel tree), tested - no luck.
I added ld-linux.so (2 files: ld-2.13.so with symbolic link), tested - same error.
Busybox way allows to run binaries without any of this libraries, tested by me on ARM platform.
Thanks for trying to help me, any other ideas?
$ printf 'int main(){}' | gcc -static -x c - -o hello
$ scp hello vi-server.org:./
hello 100% 565KB 565.2KB/s 00:00
$ ssh -t vi-server.org "./hello; uname -r"
FATAL: kernel too old
sh: line 1: 15378 Segmentation fault ./hello
2.6.18-274.... # can't easily upgrade the kernel
Connection to vi-server.org closed.
How to build static binary that will work on on old systems? I expect static binaries to work even on 2.4.
You need to configure glibc to target the older kernel version. Per http://www.gnu.org/software/libc/manual/html_node/Configuring-and-compiling.html glibc accepts the configure option --enable-kernel=version where version is in the form 2.4.20 to target older kernel versions.
You can then link your program statically with gcc -static -nodefaultlibs [...] /path/to/my/libc.a.
Thank you to the above poster ecatmur -- it does indeed work to reconfigure/rebuild glibc with the configure option --enable-kernel=version
I would add the following -- you can use gcc -static -L/path/to/local/lib (big L option to the directory) and it seems to work just as well as linking to the library file itself. When I linked in the latter fashion (to /path/to/local/lib/libc.a), it created an unecessarily large executable.
I am new to Cuda, and I am trying to compile this simple test_1.cu file:
#include <stdio.h>
__global__ void kernel(void)
{
}
int main (void)
{
kernel<<<1,1>>>();
printf( "Hello, World!\n");
return 0;
}
using this: nvcc test_1.cu
The output I get is:
In file included from /usr/local/cuda/bin/../include/cuda_runtime.h:59:0,
from <command-line>:0:
/usr/local/cuda/bin/../include/host_config.h:82:2: error: #error -- unsupported GNU version! gcc 4.5 and up are not supported!
my gcc --version:
gcc (Ubuntu/Linaro 4.6.1-9ubuntu3) 4.6.1
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
How can I install a second version of gcc (4.4 -) along with 4.6 without messing everything up?
I found this old topic:
CUDA incompatible with my gcc version
the answer was:
gcc 4.5 and 4.6 are not supported with CUDA - code won't compile and
the rest of the toolchain, including cuda-gdb, won't work properly.
You cannot use them, and the restriction is non-negotiable.
Your only solution is to install a gcc 4.4 version as a second
compiler (most distributions will allow that). There is an option to
nvcc --compiler-bindir which can be used to point to an alternative
compiler. Create a local directory and the make symbolic links to the
supported gcc version executables. Pass that local directory to nvcc
via the --compiler-bindir option, and you should be able to compile
CUDA code without effecting the rest of your system.
But I have no idea how to do it
In my case I didn't have root rights, so I couldn't fully replace the current gcc (4.7) with the older version 4.4 (which I think would be a bad alternative). Although I did have rights where CUDA was installed. My solution was to create an extra folder (e.g. /somepath/gccfornvcc/), wherever I had rights, then to create a link to an nvcc accepted compiler. I already had gcc 4.4 available (but you can install it, without removing your current version).
ln -s [path to gcc 4.4]/gcc-4.4 /somepath/gccfornvcc/gcc
Then, in the same folder where the nvcc binary lives, you should find a file called nvcc.profile . There you just need to add the following line:
compiler-bindir = /somepath/gccfornvcc
And that will make nvcc use the proper compiler. This helps keeping the system in a proper state, keeping the newest compiler, but nvcc (only nvcc) will use the old compiler version.
Doing some research online shows several methods for accomplishing this task. I just tested the method found here: http://www.vectorfabrics.com/blog/item/cuda_4.0_on_ubuntu_11.04 and it worked like a charm for me. It steps you through installing gcc 4.4 and creating scripts to run that version with nvcc. If you prefer trying the method mentioned in your post I'd recommend following that first link to install gcc4.4 and then create symbolic links as mentioned in your post. Creating symbolic links in Linux is accomplished by using the 'ln' command.
For example:
ln -s [source file/folder path] [linkpath]
This link gives a few examples of creating symbolic links on both Ubuntu and Windows: http://www.howtogeek.com/howto/16226/complete-guide-to-symbolic-links-symlinks-on-windows-or-linux/. Hopefully that points you in the right direction.
I guess you may try the new, beta, version, that based on LLVM.
Another way to make nvcc work with non-default compiler (unlike #Sluml's answer, it allows more flexibility):
At first, just like #Slump proposed, you need to create directory ~/local/gcc-4.4/, and then create there symlinks for right versions of gcc: for i in gcc gxx; do ln -s /usr/bin/${i}-4.4 ~/local/cudagcc/${i}; done. Now when you run nvcc -ccbin ~/local/gcc-4.4/ ... nvcc will use correct versions of gcc.
Here is small CMake snippet of forcing nvcc use specific host compiler.
option (CUDA_ENFORCE_HOST_COMPILER "Force nvcc to use the same compiler used to compile .c(pp) files insted of gcc/g++" OFF)
if (${CUDA_ENFORCE_HOST_COMPILER})
set (CMAKE_GCC_TEMP_DIR "CMakeGCC")
file(MAKE_DIRECTORY ${CMAKE_GCC_TEMP_DIR})
execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink ${CMAKE_C_COMPILER} ${CMAKE_GCC_TEMP_DIR}/gcc)
execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink ${CMAKE_CXX_COMPILER} ${CMAKE_GCC_TEMP_DIR}/g++)
set(CUDA_NVCC_FLAGS -ccbin ${CMAKE_GCC_TEMP_DIR} ${CUDA_NVCC_FLAGS})
endif()
Reference：
I update my gcc from 4.4 to 4.6. Then I could not use nvcc to compile my code. Luckily, by using the method provided by the following link. I set my default gcc compiler back to gcc 4.4. Now, I could compile file using either gcc4.4 or gcc4.6. quit cool
http://ubuntuguide.net/how-to-install-and-setup-gcc-4-1g4-1-in-ubuntu-10-0410-10
When I compile something on my Ubuntu Lucid 10.04 PC it gets linked against glibc. Lucid uses 2.11 of glibc. When I run this binary on another PC with an older glibc, the command fails saying there's no glibc 2.11...
As far as I know glibc uses symbol versioning. Can I force gcc to link against a specific symbol version?
In my concrete use I try to compile a gcc cross toolchain for ARM.
You are correct in that glibc uses symbol versioning. If you are curious, the symbol versioning implementation introduced in glibc 2.1 is described here and is an extension of Sun's symbol versioning scheme described here.
One option is to statically link your binary. This is probably the easiest option.
You could also build your binary in a chroot build environment, or using a glibc-new => glibc-old cross-compiler.
According to the http://www.trevorpounds.com blog post Linking to Older Versioned Symbols (glibc), it is possible to to force any symbol to be linked against an older one so long as it is valid by using the same .symver pseudo-op that is used for defining versioned symbols in the first place. The following example is excerpted from the blog post.
The following example makes use of glibc’s realpath, but makes sure it is linked against an older 2.2.5 version.
#include <limits.h>
#include <stdlib.h>
#include <stdio.h>
__asm__(".symver realpath,realpath#GLIBC_2.2.5");
int main()
{
const char* unresolved = "/lib64";
char resolved[PATH_MAX+1];
if(!realpath(unresolved, resolved))
{ return 1; }
printf("%s\n", resolved);
return 0;
}
Setup 1: compile your own glibc without dedicated GCC and use it
Since it seems impossible to do just with symbol versioning hacks, let's go one step further and compile glibc ourselves.
This setup might work and is quick as it does not recompile the whole GCC toolchain, just glibc.
But it is not reliable as it uses host C runtime objects such as crt1.o, crti.o, and crtn.o provided by glibc. This is mentioned at: https://sourceware.org/glibc/wiki/Testing/Builds?action=recall&rev=21#Compile_against_glibc_in_an_installed_location Those objects do early setup that glibc relies on, so I wouldn't be surprised if things crashed in wonderful and awesomely subtle ways.
For a more reliable setup, see Setup 2 below.
Build glibc and install locally:
export glibc_install="$(pwd)/glibc/build/install"
git clone git://sourceware.org/git/glibc.git
cd glibc
git checkout glibc-2.28
mkdir build
cd build
../configure --prefix "$glibc_install"
make -j `nproc`
make install -j `nproc`
Setup 1: verify the build
test_glibc.c
#define _GNU_SOURCE
#include <assert.h>
#include <gnu/libc-version.h>
#include <stdatomic.h>
#include <stdio.h>
#include <threads.h>
atomic_int acnt;
int cnt;
int f(void* thr_data) {
for(int n = 0; n < 1000; ++n) {
++cnt;
++acnt;
}
return 0;
}
int main(int argc, char **argv) {
/* Basic library version check. */
printf("gnu_get_libc_version() = %s\n", gnu_get_libc_version());
/* Exercise thrd_create from -pthread,
* which is not present in glibc 2.27 in Ubuntu 18.04.
* https://stackoverflow.com/questions/56810/how-do-i-start-threads-in-plain-c/52453291#52453291 */
thrd_t thr[10];
for(int n = 0; n < 10; ++n)
thrd_create(&thr[n], f, NULL);
for(int n = 0; n < 10; ++n)
thrd_join(thr[n], NULL);
printf("The atomic counter is %u\n", acnt);
printf("The non-atomic counter is %u\n", cnt);
}
Compile and run with test_glibc.sh:
#!/usr/bin/env bash
set -eux
gcc \
-L "${glibc_install}/lib" \
-I "${glibc_install}/include" \
-Wl,--rpath="${glibc_install}/lib" \
-Wl,--dynamic-linker="${glibc_install}/lib/ld-linux-x86-64.so.2" \
-std=c11 \
-o test_glibc.out \
-v \
test_glibc.c \
-pthread \
;
ldd ./test_glibc.out
./test_glibc.out
The program outputs the expected:
gnu_get_libc_version() = 2.28
The atomic counter is 10000
The non-atomic counter is 8674
Command adapted from https://sourceware.org/glibc/wiki/Testing/Builds?action=recall&rev=21#Compile_against_glibc_in_an_installed_location but --sysroot made it fail with:
cannot find /home/ciro/glibc/build/install/lib/libc.so.6 inside /home/ciro/glibc/build/install
so I removed it.
ldd output confirms that the ldd and libraries that we've just built are actually being used as expected:
+ ldd test_glibc.out
linux-vdso.so.1 (0x00007ffe4bfd3000)
libpthread.so.0 => /home/ciro/glibc/build/install/lib/libpthread.so.0 (0x00007fc12ed92000)
libc.so.6 => /home/ciro/glibc/build/install/lib/libc.so.6 (0x00007fc12e9dc000)
/home/ciro/glibc/build/install/lib/ld-linux-x86-64.so.2 => /lib64/ld-linux-x86-64.so.2 (0x00007fc12f1b3000)
The gcc compilation debug output shows that my host runtime objects were used, which is bad as mentioned previously, but I don't know how to work around it, e.g. it contains:
COLLECT_GCC_OPTIONS=/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crt1.o
Setup 1: modify glibc
Now let's modify glibc with:
diff --git a/nptl/thrd_create.c b/nptl/thrd_create.c
index 113ba0d93e..b00f088abb 100644
--- a/nptl/thrd_create.c
+++ b/nptl/thrd_create.c
## -16,11 +16,14 ##
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <stdio.h>
+
#include "thrd_priv.h"
int
thrd_create (thrd_t *thr, thrd_start_t func, void *arg)
{
+ puts("hacked");
_Static_assert (sizeof (thr) == sizeof (pthread_t),
"sizeof (thr) != sizeof (pthread_t)");
Then recompile and re-install glibc, and recompile and re-run our program:
cd glibc/build
make -j `nproc`
make -j `nproc` install
./test_glibc.sh
and we see hacked printed a few times as expected.
This further confirms that we actually used the glibc that we compiled and not the host one.
Tested on Ubuntu 18.04.
Setup 2: crosstool-NG pristine setup
This is an alternative to setup 1, and it is the most correct setup I've achieved far: everything is correct as far as I can observe, including the C runtime objects such as crt1.o, crti.o, and crtn.o.
In this setup, we will compile a full dedicated GCC toolchain that uses the glibc that we want.
The only downside to this method is that the build will take longer. But I wouldn't risk a production setup with anything less.
crosstool-NG is a set of scripts that downloads and compiles everything from source for us, including GCC, glibc and binutils.
Yes the GCC build system is so bad that we need a separate project for that.
This setup is only not perfect because crosstool-NG does not support building the executables without extra -Wl flags, which feels weird since we've built GCC itself. But everything seems to work, so this is only an inconvenience.
Get crosstool-NG and configure it:
git clone https://github.com/crosstool-ng/crosstool-ng
cd crosstool-ng
git checkout a6580b8e8b55345a5a342b5bd96e42c83e640ac5
export CT_PREFIX="$(pwd)/.build/install"
export PATH="/usr/lib/ccache:${PATH}"
./bootstrap
./configure --enable-local
make -j `nproc`
./ct-ng x86_64-unknown-linux-gnu
./ct-ng menuconfig
The only mandatory option that I can see, is making it match your host kernel version to use the correct kernel headers. Find your host kernel version with:
uname -a
which shows me:
4.15.0-34-generic
so in menuconfig I do:
Operating System
Version of linux
so I select:
4.14.71
which is the first equal or older version. It has to be older since the kernel is backwards compatible.
Now you can build with:
env -u LD_LIBRARY_PATH time ./ct-ng build CT_JOBS=`nproc`
and now wait for about thirty minutes to two hours for compilation.
Setup 2: optional configurations
The .config that we generated with ./ct-ng x86_64-unknown-linux-gnu has:
CT_GLIBC_V_2_27=y
To change that, in menuconfig do:
C-library
Version of glibc
save the .config, and continue with the build.
Or, if you want to use your own glibc source, e.g. to use glibc from the latest git, proceed like this:
Paths and misc options
Try features marked as EXPERIMENTAL: set to true
C-library
Source of glibc
Custom location: say yes
Custom location
Custom source location: point to a directory containing your glibc source
where glibc was cloned as:
git clone git://sourceware.org/git/glibc.git
cd glibc
git checkout glibc-2.28
Setup 2: test it out
Once you have built he toolchain that you want, test it out with:
#!/usr/bin/env bash
set -eux
install_dir="${CT_PREFIX}/x86_64-unknown-linux-gnu"
PATH="${PATH}:${install_dir}/bin" \
x86_64-unknown-linux-gnu-gcc \
-Wl,--dynamic-linker="${install_dir}/x86_64-unknown-linux-gnu/sysroot/lib/ld-linux-x86-64.so.2" \
-Wl,--rpath="${install_dir}/x86_64-unknown-linux-gnu/sysroot/lib" \
-v \
-o test_glibc.out \
test_glibc.c \
-pthread \
;
ldd test_glibc.out
./test_glibc.out
Everything seems to work as in Setup 1, except that now the correct runtime objects were used:
COLLECT_GCC_OPTIONS=/home/ciro/crosstool-ng/.build/install/x86_64-unknown-linux-gnu/bin/../x86_64-unknown-linux-gnu/sysroot/usr/lib/../lib64/crt1.o
Setup 2: failed efficient glibc recompilation attempt
It does not seem possible with crosstool-NG, as explained below.
If you just re-build;
env -u LD_LIBRARY_PATH time ./ct-ng build CT_JOBS=`nproc`
then your changes to the custom glibc source location are taken into account, but it builds everything from scratch, making it unusable for iterative development.
If we do:
./ct-ng list-steps
it gives a nice overview of the build steps:
Available build steps, in order:
- companion_tools_for_build
- companion_libs_for_build
- binutils_for_build
- companion_tools_for_host
- companion_libs_for_host
- binutils_for_host
- cc_core_pass_1
- kernel_headers
- libc_start_files
- cc_core_pass_2
- libc
- cc_for_build
- cc_for_host
- libc_post_cc
- companion_libs_for_target
- binutils_for_target
- debug
- test_suite
- finish
Use "<step>" as action to execute only that step.
Use "+<step>" as action to execute up to that step.
Use "<step>+" as action to execute from that step onward.
therefore, we see that there are glibc steps intertwined with several GCC steps, most notably libc_start_files comes before cc_core_pass_2, which is likely the most expensive step together with cc_core_pass_1.
In order to build just one step, you must first set the "Save intermediate steps" in .config option for the intial build:
Paths and misc options
Debug crosstool-NG
Save intermediate steps
and then you can try:
env -u LD_LIBRARY_PATH time ./ct-ng libc+ -j`nproc`
but unfortunately, the + required as mentioned at: https://github.com/crosstool-ng/crosstool-ng/issues/1033#issuecomment-424877536
Note however that restarting at an intermediate step resets the installation directory to the state it had during that step. I.e., you will have a rebuilt libc - but no final compiler built with this libc (and hence, no compiler libraries like libstdc++ either).
and basically still makes the rebuild too slow to be feasible for development, and I don't see how to overcome this without patching crosstool-NG.
Furthermore, starting from the libc step didn't seem to copy over the source again from Custom source location, further making this method unusable.
Bonus: stdlibc++
A bonus if you're also interested in the C++ standard library: How to edit and re-build the GCC libstdc++ C++ standard library source?
Link with -static. When you link with -static the linker embeds the library inside the executable, so the executable will be bigger, but it can be executed on a system with an older version of glibc because the program will use it's own library instead of that of the system.
In my opinion, the laziest solution (especially if you don't rely on latest bleeding edge C/C++ features, or latest compiler features) wasn't mentioned yet, so here it is:
Just build on the system with the oldest GLIBC you still want to support.
This is actually pretty easy to do nowadays with technologies like chroot, or KVM/Virtualbox, or docker, even if you don't really want to use such an old distro directly on any pc. In detail, to make a maximum portable binary of your software I recommend following these steps:
Just pick your poison of sandbox/virtualization/... whatever, and use it to get yourself a virtual older Ubuntu LTS and compile with the gcc/g++ it has in there by default. That automatically limits your GLIBC to the one available in that environment.
Avoid depending on external libs outside of foundational ones: like, you should dynamically link ground-level system stuff like glibc, libGL, libxcb/X11/wayland things, libasound/libpulseaudio, possibly GTK+ if you use that, but otherwise preferrably statically link external libs/ship them along if you can. Especially mostly self-contained libs like image loaders, multimedia decoders, etc can cause less breakage on other distros (breakage can be caused e.g. if only present somewhere in a different major version) if you statically ship them.
With that approach you get an old-GLIBC-compatible binary without any manual symbol tweaks, without doing a fully static binary (that may break for more complex programs because glibc hates that, and which may cause licensing issues for you), and without setting up any custom toolchain, any custom glibc copy, or whatever.
An alternative is to just discard the version info and let the linker default to whatever version it has.
To do this, you may want to check out PatchELF1:
$ nm --dynamic --undefined-only --with-symbol-versions MyLib.so \
| grep GLIBC | sed -e 's#.\+###' | sort --unique
GLIBC_2.17
GLIBC_2.29
$ nm --dynamic --undefined-only --with-symbol-versions MyLib.so | grep GLIBC_2.29
U exp#GLIBC_2.29
U log#GLIBC_2.29
U log2#GLIBC_2.29
U pow#GLIBC_2.29
$ patchelf --clear-symbol-version exp \
--clear-symbol-version log \
--clear-symbol-version log2 \
--clear-symbol-version pow MyLib.so
This is extremely useful if you don't have the source at hand (or have a hard time understanding the code2).
1 Although patchelf is available on many distributions, they are very likely to be outdated.
The --clear-symbol-version flag was added in version 0.12, which, unfortunately, does not fully remove version requirements.
You will need to compile manually from this merge request before it gets merged.
2 FYI, I was cross-compiling LuaJIT.
This repo:
https://github.com/wheybags/glibc_version_header
provides a header file that takes care of the details described in the accepted answer.
Basically:
Download the header of the corresponding GCC you want to link against
Add -include /path/to/header.h to your compiler flags
You may also need to add -D_REENTRANT if you're linking pthread
I also add the linker flags:
-static-libgcc -static-libstdc++ -pthread
But those are dependent on your app's requirements.