Ubuntu
llvm-3.0 package

clang -O4 -use-gold-plugin fails (LLVMgold.so: undefined symbol: lto_codegen_compile_to_file)

Bug #1026359 reported by Anders Kaseorg on 2012-07-18

This bug affects 4 people

	Status	Importance	Assigned to
LLVM	Fix Released	Wishlist	llvm #13262
llvm-3.0 (Ubuntu)	Fix Released	Undecided	Unassigned
llvm-3.1 (Ubuntu)	Fix Released	Undecided	Unassigned

Bug Description

$ echo 'int main(){return 0;}' > foo.c
$ clang -O4 -use-gold-plugin foo.c
/usr/bin/ld.gold.real: error: /usr/bin/../lib/LLVMgold.so: could not load plugin library: /usr/bin/../lib/LLVMgold.so: undefined symbol: lto_codegen_compile_to_file
/usr/bin/ld.gold.real: error: /tmp/foo-KzG9X9.o:1:3: invalid character
/usr/bin/ld.gold.real: error: /tmp/foo-KzG9X9.o:1:3: syntax error, unexpected $end
/usr/bin/ld.gold.real: error: /tmp/foo-KzG9X9.o: not an object or archive
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o(.text+0x20): error: undefined reference to 'main'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ ld.gold -v -plugin /usr/lib/llvm-3.0/lib/LLVMgold.so
GNU gold (GNU Binutils for Ubuntu 2.22.52.20120713) 1.11
/usr/bin/ld.gold.real: error: /usr/lib/llvm-3.0/lib/LLVMgold.so: could not load plugin library: /usr/lib/llvm-3.0/lib/LLVMgold.so: undefined symbol: lto_codegen_compile_to_file

It seems that LLVMgold.so is missing a dependency on libLTO.so. Things work if I set that as an LD_PRELOAD.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: llvm-3.0-dev 3.0-9
ProcVersionSignature: Ubuntu 3.5.0-4.4-generic 3.5.0-rc6
Uname: Linux 3.5.0-4-generic x86_64
NonfreeKernelModules: openafs nvidia
ApportVersion: 2.4-0ubuntu2
Architecture: amd64
Date: Wed Jul 18 18:20:18 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20101202)
SourcePackage: llvm-3.0
UpgradeStatus: No upgrade log present (probably fresh install)

Tags:

Related branches

lp:ubuntu/quantal/llvm-3.0

lp:ubuntu/quantal/llvm-3.1

lp:ubuntu/saucy-proposed/llvm-3.0

Revision history for this message

In LLVM #13262, Felix Geyer (debfx) wrote on 2012-07-03:

Created attachment 8821
Patch to pass LTO flags to LDFLAGS and LIBS

LLVMgold.so is not linked against libLTO.so when ld defaults to --as-needed (which is the default on Ubuntu and afaik Fedora).

LLVMgold is built like this:
x86_64-linux-gnu-g++ [...] -lLTO [...] -o /build/buildd/llvm-3.1-3.1/build-llvm/Release/lib/LLVMgold.so /build/buildd/llvm-3.1-3.1/build-llvm/tools/gold/Release/gold-plugin.o [...] -lpthread -lffi -ldl -lm

-lLTO is passed before gold-plugin.o so it is ignored.

I'm attaching a patch that adds "-L$(SharedLibDir)/$(SharedPrefix)" to LDFLAGS and "-lLTO" to LIBS instead of appending both to CXXFLAGS.
Makefile.config overwrites LIBS so I've added that at the bottom of the Makefile.
Maybe there is a better solution for this?

With these changes LLVMgold is built like this:
x86_64-linux-gnu-g++ [...] -o /tmp/buildd/llvm-3.1-3.1/build-llvm/Release/lib/LLVMgold.so /tmp/buildd/llvm-3.1-3.1/build-llvm/tools/gold/Release/gold-plugin.o [...] -lpthread -lffi -ldl -lm -lLTO

Revision history for this message

In LLVM #13262, Rafael Ávila de Espíndola (rafael-espindola) wrote on 2012-07-03:

cmake gets this right:

g++ -fPIC -fPIC -fvisibility-inlines-hidden -fno-rtti -O3 -DNDEBUG -shared -Wl,-soname,LLVMgold.so -o lib/LLVMgold.so tools/gold/CMakeFiles/LLVMgold.dir/gold-plugin.cpp.o ... -lpthread lib/libLTO.so ....

Revision history for this message

Anders Kaseorg (andersk) wrote on 2012-07-18:

Dependencies.txt Edit (556 bytes, text/plain; charset="utf-8")
ProcEnviron.txt Edit (297 bytes, text/plain; charset="utf-8")

Revision history for this message

Anders Kaseorg (andersk) wrote on 2012-07-18:

This is a difference between Debian’s llvm-3.0-dev binary and Ubuntu’s llvm-3.0-dev binary, even though they are the same version compiled from the same source.

$ diff -u \
    <(objdump -p llvm-3.0-dev_3.0-9_debian/usr/lib/llvm-3.0/lib/LLVMgold.so | grep NEEDED) \
    <(objdump -p llvm-3.0-dev_3.0-9_ubuntu/usr/lib/llvm-3.0/lib/LLVMgold.so | grep NEEDED)
--- /dev/fd/63 2012-07-18 18:35:22.399421588 -0400
+++ /dev/fd/62 2012-07-18 18:35:22.403421684 -0400
@@ -1,9 +1,4 @@
- NEEDED libLTO.so
   NEEDED libLLVM-3.0.so.1
   NEEDED libpthread.so.0
- NEEDED libffi.so.5
- NEEDED libdl.so.2
   NEEDED libstdc++.so.6
- NEEDED libm.so.6
- NEEDED libgcc_s.so.1
   NEEDED libc.so.6

Bug Watch Updater (bug-watch-updater) on 2012-08-08

Changed in llvm:
importance:	Unknown → Wishlist
status:	Unknown → Confirmed

Revision history for this message

In LLVM #13262, Wladimir J. van der Laan (laanwj) wrote on 2012-08-26:

I also noticed this problem with latest SVN build (r162623) on Ubuntu 12.04. LLVMgold.so was not linked to libLTO.so, which caused problems when using it:

/usr/bin/ld: error: /opt/clang/bin/../lib/LLVMgold.so: could not load plugin library: /opt/clang/bin/../lib/LLVMgold.so: undefined symbol: lto_codegen_add_must_preserve_symbol

Using the above patch solved the problem.

Revision history for this message

In LLVM #13262, Rafael Ávila de Espíndola (rafael-espindola) wrote on 2012-08-27:

#15

Fixed by applying your patch in 162652. Sorry it took so long.

Revision history for this message

Launchpad Janitor (janitor) wrote on 2012-08-27:

This bug was fixed in the package llvm-3.0 - 3.0-9ubuntu1

---------------
llvm-3.0 (3.0-9ubuntu1) quantal; urgency=low

  * Link LLVMgold.so against libLTO which was broken due to ld --as-needed.
    (LP: #1026359)
    - Add 1001-link-llvmgold-lto.diff, cherry-picked from upstream.
-- Felix Geyer <email address hidden> Mon, 27 Aug 2012 19:36:55 +0200

Changed in llvm-3.0 (Ubuntu):
status:	New → Fix Released

Revision history for this message

Felix Geyer (debfx) wrote on 2012-08-27:

llvm-3.1_3.1-2ubuntu1.debdiff Edit (2.7 KiB, text/plain)

Please consider sponsoring the same fix for llvm-3.1.

Revision history for this message

Launchpad Janitor (janitor) wrote on 2012-08-27:

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in llvm-3.1 (Ubuntu):
status:	New → Confirmed

Revision history for this message

Dimitri John Ledkov (xnox) wrote on 2012-08-28:

Testing to sponsor this.

Revision history for this message

Dimitri John Ledkov (xnox) wrote on 2012-08-28:

#10

While the patch does indeed links the plugin correctly the original example still does not work in multiple ways.

I have installed clang & llvm-3.0 packages:

$ dpkg-query -W llvm-3.0
llvm-3.0 3.0-9ubuntu1
$ dpkg-query -W clang
clang 3.0-6ubuntu3
$ cat foo.c
int main(){return 0;}
$ clang -O4 -use-gold-plugin foo.c
/usr/bin/ld.bfd.real: /usr/bin/../lib/LLVMgold.so: error loading plugin
/usr/bin/ld.bfd.real: /usr/bin/../lib/LLVMgold.so: error in plugin cleanup (ignored)
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ ld.gold -v -plugin /usr/lib/llvm-3.0/lib/LLVMgold.so
GNU gold (GNU Binutils for Ubuntu 2.22.90.20120816) 1.11
/usr/bin/ld.gold.real: error: /usr/lib/llvm-3.0/lib/LLVMgold.so: could not load plugin library: libLTO.so: cannot open shared object file: No such file or directory

So there is a missing dependency.... on llvm-dev (well current default llvm-3.0-dev)
To me this sounds a bit counter-intuitive, but maybe that's just the way to package llvm.
But why split the packages, if they still depend on each other....?

After installing llvm-dev I get slightly better results:

$ clang -O4 -use-gold-plugin foo.c -o foo
/tmp/foo-nf9h1L.o: file not recognized: File format not recognised
clang: error: linker command failed with exit code 1 (use -v to see invocation)

but...

$ clang -O3 -use-gold-plugin foo.c -o foo && echo $?
0

So is -O4 broken with gold linker?

This fix looks sane and I can test is by inspection with ldd, but can I tell clang to use a different LLVM? Cause clang is currently compiled against llvm-3.0, not llvm-3.1.

Revision history for this message

Dimitri John Ledkov (xnox) wrote on 2012-08-28:

#11

To build the source package, I had to further modify the source file of the generated control file....

diff -Nru llvm-3.1-3.1/debian/control.in/source llvm-3.1-3.1/debian/control.in/source
--- llvm-3.1-3.1/debian/control.in/source 2012-04-19 19:45:00.000000000 +0100
+++ llvm-3.1-3.1/debian/control.in/source 2012-08-28 15:15:09.000000000 +0100
@@ -1,7 +1,8 @@
Source: @PKGSOURCE@
Section: devel
Priority: optional
-Maintainer: LLVM Packaging Team <email address hidden>
+Maintainer: Ubuntu Developers <email address hidden>
+XSBC-Original-Maintainer: LLVM Packaging Team <email address hidden>
Uploaders: Arthur Loiret <email address hidden>, Sylvestre Ledru <email address hidden>
Build-Depends: debhelper (>= 8.1.3), flex, bison, dejagnu, tcl8.5, expect,
autoconf, automake1.9, perl, libtool, doxygen, chrpath, texinfo, quilt,

Revision history for this message

Launchpad Janitor (janitor) wrote on 2012-08-28:

#12

This bug was fixed in the package llvm-3.1 - 3.1-2ubuntu1

---------------
llvm-3.1 (3.1-2ubuntu1) quantal; urgency=low

Changed in llvm-3.1 (Ubuntu):
status:	Confirmed → Fix Released

Revision history for this message

Dimitri John Ledkov (xnox) wrote on 2012-08-28:

#13

I have also filed:
bug 1042822
bug 1042819

Revision history for this message

Felix Geyer (debfx) wrote on 2012-08-28:

#14

Thanks.
I guess I shouldn't blindly trust update-maintainer. So many ways too preprocess the control file ...

Bug Watch Updater (bug-watch-updater) on 2012-08-30

Changed in llvm:
status:	Confirmed → Fix Released

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clang -O4 -use-gold-plugin fails (LLVMgold.so: undefined symbol: lto_codegen_compile_to_file)

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