[LLVMdev] How to compile apps to bc files with the new llvm-gcc4?

Chandler Carruth chandlerc at gmail.com
Sun Dec 10 07:53:50 PST 2006

Unless I'm missing something, the problem lies directly with the fact that
you are trying to do a link-stage operation with the GCC frontend. GCC, by
default, probably runs "ld" or another system linker, which grabs the
executable from binutils. This linker hasn't been modified (yet) to include
support for .bc files, but you're compiler is emitting byte code to the *.o
files. That is why the linker barfs, and tries to interpret as a script.

I am actually planning on working on integration between binutils' ld and
LLVM to allow just this functionality. I'll be working on this over the
holidays, and hopefully will get something working by mid January. Until
then, directly using the LLVM linking facilities to handle the bytecode is
probably the best if not only option.


PS: I'm still kinda new, so someone else may come along and correct me, but
that's the best I can figure out...

On 12/10/06, Domagoj Babic <babic.domagoj at gmail.com> wrote:
> Hi,
> I'm trying to compile some apps with the new llvm-gcc4 on amd64 linux
> to .bc files, rather than to the native code. The same process I used to
> build those apps before with llvm-gcc3 doesn't work:
> 1)
> export CC=llvm-gcc CXX=llvm-g++ CFLAGS="-g -fno-inline" CXXFLAGS="-g
> -fno-inline"
> 2) cd <whatever-app>; ./configure
> 3) make CFLAGS+=-emit-llvm CXXFLAGS+=-emit-llvm
> [Reid told me not to pass -emit-llvm to configure scripts.]
> The process fails for the same reason on several apps I tried:
> --------------------------------------------------------------
> $ llvm-gcc -shared  .libs/libdspam.o .libs/heap.o .libs/diction.o
> .libs/base64.o .libs/buffer.o .libs/util.o .libs/nodetree.o
> .libs/error.o .libs/decode.o .libs/pref.o .libs/config_shared.o
> .libs/bnr.o .libs/hash.o .libs/list.o .libs/ldap_client.o
> .libs/tokenizer.o .libs/hash_drv.o  -lm -ldl  -Wl,-soname
> -Wl,libdspam.so.7 -o .libs/libdspam.so.7.0.0 -v
> Using built-in specs.
> Target: x86_64-unknown-linux-gnu
> Configured with: ../dst-directory/configure --disable-shared
> --prefix=/usr/local/devapps/llvm --enable-languages=c,c++
> --enable-llvm=/work/projects/llvm-obj --program-prefix=llvm-
> --enable-checking --disable-multilib
> Thread model: posix
> gcc version 4.0.1 LLVM (Apple Computer, Inc. build 5421)
> /usr/local/devapps/llvm/libexec/gcc/x86_64-unknown-linux-gnu/4.0.1/collect2
> --eh-frame-hdr -m elf_x86_64 -shared -o .libs/libdspam.so.7.0.0
> /usr/lib/../lib64/crti.o
> /usr/local/devapps/llvm/lib/gcc/x86_64-unknown-linux-gnu/4.0.1/crtbeginS.o
> -L/usr/local/devapps/llvm/lib/gcc/x86_64-unknown-linux-gnu/4.0.1
> -L/usr/local/devapps/llvm/lib/gcc/x86_64-unknown-linux-gnu/4.0.1/../../../../lib64
> -L/usr/local/devapps/llvm/lib/gcc/x86_64-unknown-linux-gnu/4.0.1/../../..
> -L/lib/../lib64 -L/usr/lib/../lib64 .libs/libdspam.o .libs/heap.o
> .libs/diction.o .libs/base64.o .libs/buffer.o .libs/util.o
> .libs/nodetree.o .libs/error.o .libs/decode.o .libs/pref.o
> .libs/config_shared.o .libs/bnr.o .libs/hash.o .libs/list.o
> .libs/ldap_client.o .libs/tokenizer.o .libs/hash_drv.o -lm -ldl
> -soname libdspam.so.7 -lgcc -lc -lgcc
> /usr/local/devapps/llvm/lib/gcc/x86_64-unknown-linux-gnu/4.0.1/crtendS.o
> /usr/lib/../lib64/crtn.o
> /usr/bin/ld:.libs/libdspam.o: file format not recognized; treating as
> linker script
> /usr/bin/ld:.libs/libdspam.o:1: syntax error
> collect2: ld returned 1 exit status
> --------------------------------------------------------------
> If I execute the last command manually with llvm-ld, removing -shared
> and -Wl, it goes through.
> So, obviously I'm doing something wrong.
> What do I need to change in the build process to compile the same apps
> I could compile before with llvm-gcc3 to bc files?
> Thx in advance,
>             Domagoj
> _______________________________________________
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