llvm dev - Sep 2015 - Building clang in llvm-3.7 on Linux with RT support enabled

Hi All,

I need to build clang/llvm from source on an Ubuntu Linux system, in order to
build the gnustep Objective-C environment.  I was able to build clang using
cmake without a problem (following the instructions at
clang.llvm.org/get_started.html), but when I tried to build gnustep, I found
that clang failed to compile an autoconf-generated program.  The compile error
in the configure log was:

configure:14781: checking for _Block_copy
configure:14837: clang -o conftest -m64 -march=opteron -mno-3dnow -ggdb -O2
-Wall 
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Headers 
-fgnu-runtime -x objective-c -m64 
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
conftest.c -lrt -ldl  -lpthread -rdynamic -m64 -fgnu-runtime
-L/home/dlobron/GNUstep/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
-lobjc -lm     >&5
/tmp/conftest-a47ae0.o: In function `main':
/home/dlobron/build/clangport/akamai/gnustep-base/gnustep-base-1.24.8/conftest.c:140:
undefined reference to `_Block_copy'

The line in the auto-generated conftest.c that caused the failure is:

 return _Block_copy ();

I repeated the above command from the command line, and verified that I get the
same error.

I did some searching of docs and comments, and I it sounds like I need the
realtime project to be built.  I did download the llvm/projects/compiler-rt
source, but the Makefile in llvm/projects filters it out:

# Don't build compiler-rt, it isn't designed to be built directly.
DIRS := $(filter-out compiler-rt,$(DIRS))

The main source dir of llvm has an LLVM_BUILD_EXTERNAL_COMPILER_RT option, but I
wasn't sure if I that would put RT support into clang (which I'd like)
or rather, irf it would build a separate RT compiler.

Can you guys advise me how to build clang on Linux so that _Block_copy will be
useable?

Thank you,

David

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As far as I know the makefile in there isn't the makefile that gets executed
during the cmake build -- cmake generates its own build files from
CMakeLists.txt and runs those instead. Having the compiler-rt source in
projects/compiler-rt should be enough to have its functionality built into clang
when building with cmake.

-Alex
> On Sep 29, 2015, at 11:43 AM, David Lobron via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi All,
> 
> I need to build clang/llvm from source on an Ubuntu Linux system, in order
to build the gnustep Objective-C environment.  I was able to build clang using
cmake without a problem (following the instructions at
clang.llvm.org/get_started.html), but when I tried to build gnustep, I found
that clang failed to compile an autoconf-generated program.  The compile error
in the configure log was:
> 
> configure:14781: checking for _Block_copy
> configure:14837: clang -o conftest -m64 -march=opteron -mno-3dnow -ggdb -O2
-Wall 
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Headers 
-fgnu-runtime -x objective-c -m64 
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
conftest.c -lrt -ldl  -lpthread -rdynamic -m64 -fgnu-runtime
-L/home/dlobron/GNUstep/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
-lobjc -lm     >&5
> /tmp/conftest-a47ae0.o: In function `main':
>
/home/dlobron/build/clangport/akamai/gnustep-base/gnustep-base-1.24.8/conftest.c:140:
undefined reference to `_Block_copy'
> 
> The line in the auto-generated conftest.c that caused the failure is:
> 
> return _Block_copy ();
> 
> I repeated the above command from the command line, and verified that I get
the same error.
> 
> I did some searching of docs and comments, and I it sounds like I need the
realtime project to be built.  I did download the llvm/projects/compiler-rt
source, but the Makefile in llvm/projects filters it out:
> 
> # Don't build compiler-rt, it isn't designed to be built directly.
> DIRS := $(filter-out compiler-rt,$(DIRS))
> 
> The main source dir of llvm has an LLVM_BUILD_EXTERNAL_COMPILER_RT option,
but I wasn't sure if I that would put RT support into clang (which I'd
like) or rather, irf it would build a separate RT compiler.
> 
> Can you guys advise me how to build clang on Linux so that _Block_copy will
be useable?
> 
> Thank you,
> 
> David
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Building the BlocksRuntime isn’t supported via CMake at the moment. It should be
pretty straightforward to make it work, but it currently isn’t supported.

-Chris
> On Sep 29, 2015, at 9:45 AM, Alex Wang via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> As far as I know the makefile in there isn't the makefile that gets
executed during the cmake build -- cmake generates its own build files from
CMakeLists.txt and runs those instead. Having the compiler-rt source in
projects/compiler-rt should be enough to have its functionality built into clang
when building with cmake.
> 
> -Alex
> 
>> On Sep 29, 2015, at 11:43 AM, David Lobron via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>> 
>> Hi All,
>> 
>> I need to build clang/llvm from source on an Ubuntu Linux system, in
order to build the gnustep Objective-C environment.  I was able to build clang
using cmake without a problem (following the instructions at
clang.llvm.org/get_started.html), but when I tried to build gnustep, I found
that clang failed to compile an autoconf-generated program.  The compile error
in the configure log was:
>> 
>> configure:14781: checking for _Block_copy
>> configure:14837: clang -o conftest -m64 -march=opteron -mno-3dnow -ggdb
-O2 -Wall 
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Headers
-I/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Headers 
-fgnu-runtime -x objective-c -m64 
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
conftest.c -lrt -ldl  -lpthread -rdynamic -m64 -fgnu-runtime
-L/home/dlobron/GNUstep/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/Local/Library/Libraries
-L/home/dlobron/build/clangport/akamai/common/GNUstep/System/Library/Libraries
-lobjc -lm     >&5
>> /tmp/conftest-a47ae0.o: In function `main':
>>
/home/dlobron/build/clangport/akamai/gnustep-base/gnustep-base-1.24.8/conftest.c:140:
undefined reference to `_Block_copy'
>> 
>> The line in the auto-generated conftest.c that caused the failure is:
>> 
>> return _Block_copy ();
>> 
>> I repeated the above command from the command line, and verified that I
get the same error.
>> 
>> I did some searching of docs and comments, and I it sounds like I need
the realtime project to be built.  I did download the llvm/projects/compiler-rt
source, but the Makefile in llvm/projects filters it out:
>> 
>> # Don't build compiler-rt, it isn't designed to be built
directly.
>> DIRS := $(filter-out compiler-rt,$(DIRS))
>> 
>> The main source dir of llvm has an LLVM_BUILD_EXTERNAL_COMPILER_RT
option, but I wasn't sure if I that would put RT support into clang (which
I'd like) or rather, irf it would build a separate RT compiler.
>> 
>> Can you guys advise me how to build clang on Linux so that _Block_copy
will be useable?
>> 
>> Thank you,
>> 
>> David
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev