I'm trying to use clang with OpenMPI. I have set the wrapper compiler using
export OMPI_CC=clang
When I try to verify the compiler mpicc is invoking by using
mpicc --showme:command
I get this error
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status
However, a sample mpi code runs fine using regular mpicc and mpirun commands, I guess its sticking back to the default mpicc compiler and not clang. I need to use certain clang functionalities for the OpenMPI code. How do I rectify this error.
Related
I'm using the following options:
touch foo.f90; gfortran -cpp -E -dM foo.f90
, but when I remove the -E flag I get this error:
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x24): undefined reference to `main'
collect2: error: ld returned 1 exit status
As I used 'touch' the file is empty.
The -E flag is described in the manual.
If you use the -E option, nothing is done except preprocessing. Some
of these options make sense only together with -E because they cause
the preprocessor output to be unsuitable for actual compilation.
It makes the compiler to print the preprocessed source code instead of compiling it. That means preprocessed by cpp, the C preprocessor.
If your source code is not a valid Fortran program, then trying to actually compile it (without the -E flag) naturally leads to some kind of error message.
I was trying to compile hello.cob to hello.c:
$ ls
hello.cob
$ cobc -x -C hello.cob
$ ls
hello.c hello.c.h hello.c.l.h hello.cob
But clang failed to compile hello.c to executable file:
$ clang hello.c
/tmp/hello-479acf.o: In function `main':
hello.c:(.text+0x1e): undefined reference to `cob_init'
hello.c:(.text+0x2a): undefined reference to `cob_stop_run'
/tmp/hello-479acf.o: In function `sampleCOBOL_':
hello.c:(.text+0x98): undefined reference to `cob_module_global_enter'
hello.c:(.text+0x133): undefined reference to `cob_display'
hello.c:(.text+0x13f): undefined reference to `cob_stop_run'
hello.c:(.text+0x15a): undefined reference to `cob_check_version'
hello.c:(.text+0x33d): undefined reference to `cob_set_cancel'
hello.c:(.text+0x38e): undefined reference to `cob_fatal_error'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Here is hello.cob (can be compiled by cobc -x hello.cob):
IDENTIFICATION DIVISION.
PROGRAM-ID. sampleCOBOL.
PROCEDURE DIVISION.
DISPLAY "Hello World!".
STOP RUN.
I'm quite sure clang doesn't fail to compile the C source as you don't ave any C compiler warnings or errors.
It cannot link the generated object file because you didn't told clang to link against libcob and there is no "magic" for clang to know where to find its symbols. Adding -lcob to your clang invocation may be enough already.
If you want to know how cobc invokes the compiler/linker add -v to your cobc invocation.
Note: if this version of cobc was built with gcc it defaults to use gcc, too. You can see this with cobc --info which also shows if any of the built-in commands is override by environment variables.
Additional note: cobc does not only call a C compiler/linker, it also generates C code specific for the compiler it was built with. The most important part concerning the C generation is -f[no-]computed-goto, just in case the C compiler complains (which it doesn't in your case).
I am just doing some simple OCCI thing, however it compiles a bit strangely
Environment:
Oracle VM: Centos7 64bit on Windows 8 64bit
gcc-c++.x86_64
Simply installed Oracle XE by double clicking the rpm (download pages says
linux 64bit)
echo $LD_LIBRARY_PATH yields:
/usr/local/lib64/:/u01/app/oracle/product/11.2.0/xe/lib/
I also tried export LD_LIBRARY_PATH=/u01/app/oracle/product/11.2.0/xe/lib/
so that it yields
/u01/app/oracle/product/11.2.0/xe/lib/
some listing command:
find /u01/app/oracle/product/11.2.0/xe/lib/ -name lib*
yields the following:
/u01/app/oracle/product/11.2.0/xe/lib/
/u01/app/oracle/product/11.2.0/xe/lib/libagtsh.so.1.0
/u01/app/oracle/product/11.2.0/xe/lib/libcell11.so
/u01/app/oracle/product/11.2.0/xe/lib/libclntsh.so.11.1
/u01/app/oracle/product/11.2.0/xe/lib/libnnz11.so
/u01/app/oracle/product/11.2.0/xe/lib/libocci.so.11.1
/u01/app/oracle/product/11.2.0/xe/lib/libclntsh.so
/u01/app/oracle/product/11.2.0/xe/lib/libocci.so
/u01/app/oracle/product/11.2.0/xe/lib/libagtsh.so
and some others....
however the compile command says ld cannot find some libraries:
g++ -o ab -I/u01/app/oracle/product/11.2.0/xe/rdbms/public/ -lnnz11 -lclntsh -locci a.cpp
/usr/bin/ld: cannot find -lnnz11
/usr/bin/ld: cannot find -lclntsh
/usr/bin/ld: cannot find -locci
collect2: error: ld returned 1 exit status
I have tried adding -L/u01/app/oracle/product/11.2.0/xe/lib/, it successfully compiles however running the program will cause it silently crashes / blocks at the simple line
Environment *env = Environment::createEnvironment();
no exceptions caught.
Does anyone know some part I did wrong? or are the two issues related?
And by the way, it USED to work like 5 hours ago, when it suddenly stopped working I reinstalled the whole VM and now it still doesn't work.
however the compile command says ld cannot find some libraries: g++ -o ab -I/u01/app/oracle/product/11.2.0/xe/rdbms/public/ -lnnz11 -lclntsh -locci a.cpp
Your command is incorrect (and the linker is right to complain). You need to tell the linker where to find the library, and you do that with -L flag:
ORACLE=/u01/app/oracle/product/11.2.0/xe
g++ -I ${ORACLE}/rdbms/public -L ${ORACLE}/lib a.cpp -lnnz11 -lclntsh -locci
(Note that your placement of source after library is also incorrect, and I fixed it above. Placement of libraries and sources on link command line matters.)
I have been using clang-3.5 to happily build bitcode versions of musl libc and
use the result to produce nice stand alone executables.
Recent attempts with clang-3.8 have not been so happy. It seems that
the bitcode clang-3.8 generates uses functions defined in
compiler-rt/lib/builtins
Typical examples of functions I find polluting the bitcode are mulxc3, mulsc3, and muldc3. I can solve this by linking against libgcc, or even the llvm alternative if I had any clear idea of what that was. Though I would rather prevent the problem from happening in the first place.
I have seen mention of flags like rtlib=compiler-rt etc, but have found precious little documentation on the subject.
So here are some simple questions.
Is it possible to prevent clang from using the compiler-rt/lib/builtins
in the emitted bitcode? Or if not
Does llvm produce a version of libgcc that I could use. Actually I would
probably build a bitcode version of it, but that is besides the point.
Love to hear some guidance on this.
Added 12/8/2016: So I will illustrate my issues with a particular workflow that
people can reproduce if they wish, or, more likely, just point out where I am being stupid.
So start by checking out:
musllv
and follow the instructions in the README.to compile (here I am using clang-3.8 on ubuntu 14.04)
WLLVM_CONFIGURE_ONLY=1 CC=wllvm ./configure --target=LLVM --build=LLVM
make
cd lib
extract-bc -b libc.a
you will also need the bitcode of a simple executable. I will use nweb.c here.
wllvm nweb.c -o nweb
extract-bc nweb
Now we can do things like:
clang -static -nostdlib nweb.bc libc.a.bc crt1.o libc.a -o nweb
This workflow goes smoothly for clang-3.5 but for clang-3.8 we get:
clang -static -nostdlib nweb.bc libc.a.bc crt1.o libc.a -o nweb
/tmp/libc-f734a3.o: In function `cpowl':
libc.a.bc:(.text+0xbb9a): undefined reference to `__mulxc3'
/tmp/libc-f734a3.o: In function `cpowf':
libc.a.bc:(.text+0x38f7d): undefined reference to `__mulsc3'
/tmp/libc-f734a3.o: In function `csqrt':
libc.a.bc:(.text+0x78fc3): undefined reference to `__muldc3'
/tmp/libc-f734a3.o: In function `cpow':
libc.a.bc:(.text+0xafafc): undefined reference to `__muldc3'
clang-3.8: error: linker command failed with exit code 1 (use -v to seeinvocation)
So as #paul-brannan points out we could try
clang -static -nostdlib --rtlib=compiler-rt nweb.bc libc.a.bc crt1.o libc.a -o nweb
But this is where I am probably being stupid, because I get:
clang-3.8: warning: argument unused during compilation: '--rtlib=compiler-rt'
irregardless of whether I use it as a linking or compiling flag.
OK so I finally managed to make headway on this. I built llvm-3.8.1 together with the compiler-rt project using wllvm and wllvm++.
One of the build products was libclang_rt.builtins-x86_64.a,
and from this archive I was able to extract the bitcode module
libclang_rt.builtins-x86_64.bc
using the command:
extract-bc -b libclang_rt.builtins-x86_64.a
This bitcode module has definitions for those pesky instrinsics like
__mulxc3, __mulsc3, and __muldc3.
Hallelujah!
I have been trying to enable the gold linker on FreeBSD to use the link time optimizations. I made gold from the binutils under /usr/ports. After building binutils using make -k install clean i got ld under /usr/bin and in the directory /usr/local/bin i got ld, ld.gold and ld.bfd.
Now while trying to use link time optimization for the simple example programs here http://llvm.org/docs/GoldPlugin.html (a.c and b.c under the heading 'Examples of Link Time Optimization') i entered the four commands as follows:
clang -flto a.c -c -o a.o
ar q a.a a.o
clang b.c -c -o b.o
clang -flto a.a b.o -o main
I got the following error:
usr/bin/ld: unrecogonized option '-plugin'
usr/bin/ld: use the --help option for usage information
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Is there the problem with the linker that ld.gold is not being called. Should I replace the ld with ld.gold? Does the linker looks in the right directiry for the .so plugins?
The LLVMgold.so and libLTO.so shared objects are in the directory /usr/local/llvm-devel/lib/.
I cannot find the directory where clang is installed. I am not sure where to make the bfd-plugins directory and add the symlinks to LLVMgold.so and libLTO.so.
I am using freebsd 10.1 release. How to enable the gold linker for link time optimizations?
also how can I enable it to be the default linker?
You may want to use ld.gold instead of ld. It is installed at /usr/local/bin/ld.gold. If you are using a Makefile, it would work by setting LD variable to ld.gold, either by modifying your Makefile or specifying it on command line. Example in case you are using lang/clang37:
gmake all CC=clang37 LD=ld.gold
EDIT:
It would be even more neat if you add -fuse-ld=gold to your LDFLAGS:
LDFLAGS=-fuse-ld=gold
I'm not sure ld.bfd allows plugins, but I could be wrong.
Your /usr/bin/ld should be a symlink to whatever linker you want. You can change which linker is used by using binutils-config. Check the man-page here: http://www.linuxhowtos.org/manpages/8/binutils-config.htm. I realise this is a Linux link, but it's directed at binutils itself rather than linux-specifically.
It should be something along the lines binutils-config --gold.
On my Gentoo box it is binutils --linker=gold
EDIT: As pointed out, binutils-config doesn't work on BSD it seems. You can still manually update the symlinks though, the downside is that there might be a few of them.
You can find out which ld is used by your compiler by using gcc -print-prog-name=ld or clang -print-prog-name=ld. The file printed should be a symlink you can re-create to point to ld.gold as oposed to ld.bfd.