I want to get exe with clang and llvm with two ways:
clang -O2 1.c -o 1.exe
clang -S -emit-llvm 1.c
llc 1.ll -filetype=obj
link 1.obj -defaultlib: ??? (MSVCRT or libcmt)
but exe files will different and first exe will faster, how to do it equal?
Or how to see what clang use like defaultlib?
hard: windows 64.
You can add the -v flag on your first command line to see the linker invocation clang will use to build your program. As to the first executable being faster, that could be because you didn't pass any optimization flags in your second case.
I don't have a Windows machine handy, but here's some example output from my mac:
$ clang -v -O2 1.c -o 1.exe
Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.3.0
Thread model: posix
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.9.0 -emit-obj -disable-free -disable-llvm-verifier -main-file-name 1.c -mrelocation-model pic -pic-level 2 -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 236.3 -v -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/5.1 -O2 -fdebug-compilation-dir /Users/carl/Desktop/example -ferror-limit 19 -fmessage-length 80 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.9.0 -fencode-extended-block-signature -fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp -o /var/folders/mk/0mblc5810cjgs0nylrkjxqbm0000gq/T/1-7ac5d9.o -x c 1.c
clang -cc1 version 5.1 based upon LLVM 3.4svn default target x86_64-apple-darwin13.3.0
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/5.1/include
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
/usr/include
/System/Library/Frameworks (framework directory)
/Library/Frameworks (framework directory)
End of search list.
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.9.0 -o 1.exe /var/folders/mk/0mblc5810cjgs0nylrkjxqbm0000gq/T/1-7ac5d9.o -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/5.1/lib/darwin/libclang_rt.osx.a
You can see the link line down at the bottom. Broken down for readability, its:
ld
-demangle
-dynamic
-arch x86_64
-macosx_version_min 10.9.0
-o 1.exe
$(OBJECT_FILE)
-lSystem
libclang_rt.osx.a
Related
I am building with Clang 9.0.0 and linking with the ld.lld linker
clang++.exe -Wall -fexceptions -m64 -O3 -Xclang -flto-visibility-public-std -std=c++2a -flto=thin -c
I:\Cpp\hello_boost\hello_codeblocks_world\hello_codeblocks_world.cpp -o obj\release\hello_codeblocks_world.o
clang++.exe -o bin\release\hello_codeblocks_world.exe obj\release\hello_codeblocks_world.o -m64 -fuse-ld=lld --strip-all
but, unlike when using the usual GCC linker LD, this option (--strip-all or -s) is not recognized
clang++: error: unsupported option '--strip-all' (or similarly with -s)
Can anyone suggest what I should be doing to strip symbols?
(My release-mode hello_world.exe size is 15 kb for GC but 230 kB for Clang :-( and this is likely to have some adverse effects for no benefit).
Is this not an option for ld.lld ?
Thanks
You might want to use:
-Xlinker --strip-all
You can use this to supply system-specific linker options that GCC does not recognize (gcc manual)
https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html
I'm needing to use custom libc++ so I'm passing -nostdinc++ for CMAKE_CXX_FLAGS. This works fine for libraries but for executables, I get this warning:
clang: warning: argument unused during compilation: '-nostdinc++' [-Wunused-command-line-argument]
Question: Why?
More details
My CMAKE_CXX_FLAGS flags passed to compiler are:
set(CMAKE_CXX_FLAGS "-nostdinc++ -isystem ${LIBCXX_INC_PATH}")
My CMAKE_EXE_LINKER_FLAGS flags passed to linked are:
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++ -lc++ -lc++abi -lm -lc -lgcc_s -lgcc -ldl -Wl,-rpath,${LIBCXX_LIB_PATH}")
Clang verbos output:
Scanning dependencies of target DroneServer
[ 98%] Building CXX object DroneServer/CMakeFiles/DroneServer.dir/home/shitals/GitHubSrc/AirSim/DroneServer/main.cpp.o
clang version 3.9.1-4ubuntu3~16.04.1 (tags/RELEASE_391/rc2)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;#m64
Selected multilib: .;#m64
"/usr/lib/llvm-3.9/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name main.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -v -dwarf-column-info -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -coverage-file /home/shitals/GitHubSrc/AirSim/build_debug/DroneServer/CMakeFiles/DroneServer.dir/home/shitals/GitHubSrc/AirSim/DroneServer/main.cpp.o -nostdinc++ -resource-dir /usr/lib/llvm-3.9/bin/../lib/clang/3.9.1 -isystem /home/shitals/GitHubSrc/AirSim/llvm-build/output/include/c++/v1 -I /home/shitals/GitHubSrc/AirSim/eigen/eigen3 -I /home/shitals/GitHubSrc/AirSim/DroneServer -I /home/shitals/GitHubSrc/AirSim/MavLinkCom/include -I /home/shitals/GitHubSrc/AirSim/external/rpclib/include -I /home/shitals/GitHubSrc/AirSim/AirLib/include -D __CLANG__ -D MSGPACK_PP_VARIADICS_MSVC=0 -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wall -Wextra -Wstrict-aliasing -Wunreachable-code -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wmissing-include-dirs -Wswitch-default -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wstrict-overflow=5 -Wswitch-default -Wundef -Wno-variadic-macros -Wno-parentheses -Wno-unused-function -Wno-unused -Wno-documentation -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /home/shitals/GitHubSrc/AirSim/build_debug/DroneServer -ferror-limit 10 -fmessage-length 286 -pthread -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o CMakeFiles/DroneServer.dir/home/shitals/GitHubSrc/AirSim/DroneServer/main.cpp.o -x c++ /home/shitals/GitHubSrc/AirSim/DroneServer/main.cpp
clang -cc1 version 3.9.1 based upon LLVM 3.9.1 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/home/shitals/GitHubSrc/AirSim/eigen/eigen3
/home/shitals/GitHubSrc/AirSim/DroneServer
/home/shitals/GitHubSrc/AirSim/MavLinkCom/include
/home/shitals/GitHubSrc/AirSim/external/rpclib/include
/home/shitals/GitHubSrc/AirSim/AirLib/include
/home/shitals/GitHubSrc/AirSim/llvm-build/output/include/c++/v1
/usr/local/include
/usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
[100%] Linking CXX executable ../output/bin/DroneServer
clang version 3.9.1-4ubuntu3~16.04.1 (tags/RELEASE_391/rc2)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;#m64
Selected multilib: .;#m64
clang: warning: argument unused during compilation: '-nostdinc++' [-Wunused-command-line-argument]
"/usr/bin/ld" -z relro --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o ../output/bin/DroneServer /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crt1.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/crtbegin.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../.. -L/usr/lib/llvm-3.9/bin/../lib -L/lib -L/usr/lib -lc++ -lc++abi -lm -lc -lgcc_s -lgcc -ldl -rpath /home/shitals/GitHubSrc/AirSim/llvm-build/output/lib CMakeFiles/DroneServer.dir/home/shitals/GitHubSrc/AirSim/DroneServer/main.cpp.o -lpthread ../output/lib/libAirLib.a ../output/lib/libMavLinkCom.a ../output/lib/libAirSim-rpclib.a -lpthread -lpthread -lc++ -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/crtend.o /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0/../../../x86_64-linux-gnu/crtn.o
[100%] Built target DroneServer
So all I am trying to do is get the names of the functions called by call instructions:
This is my simple code:
for(Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
{
for(BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI){
if(isa<CallInst>(&(*BI)) ) {
StringRef fname = cast<CallInst>(&(*BI))->getCalledFunction()->getName();
}
}
}
This is the Nasty error:
0 libLLVM-3.4.so.1 0x40f8150f llvm::sys::PrintStackTrace(_IO_FILE*) + 47
1 libLLVM-3.4.so.1 0x40f8177f
2 libLLVM-3.4.so.1 0x40f812ec
3 0x40022400 __kernel_sigreturn + 0
4 libLLVM-3.4.so.1 0x40899c74 llvm::Value::getName() const + 20
5 SkeletonPass.so 0x40027786
Stack dump:
0. Program arguments: /usr/bin/clang -cc1 -triple i386-pc-linux-gnu -emit-obj -disable-free -disable-llvm-verifier -main-file-name test_atomics.cc -mrelocation-model pic -pic-level 2 -fmath-errno -masm-verbose -mconstructor-aliases -fuse-init-array -target-cpu pentium4 -target-linker-version 2.24 -momit-leaf-frame-pointer -g -coverage-file /home/danish/Desktop/Owl/llvm/llvm-3.4/lib/Transforms/SyncProf/testing/masstree-beta-master/test_atomics.o -resource-dir /usr/bin/../lib/clang/3.4 -dependency-file .deps/test_atomics.d -MT test_atomics.o -sys-header-deps -MP -include config.h -D NDEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D NDEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D NDEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /usr/lib/llvm-3.4/include -I /usr/lib/llvm-3.4/include -I /usr/lib/llvm-3.4/include -internal-isystem /usr/include//c++/4.8 -internal-isystem /usr/include//c++/4.8/i386-linux-gnu -internal-isystem /usr/include//c++/4.8/backward -internal-isystem /usr/include//i386-linux-gnu/c++/4.8 -internal-isystem /usr/bin/../lib/gcc/i686-linux-gnu/4.8/../../../../include/c++/4.8 -internal-isystem /usr/bin/../lib/gcc/i686-linux-gnu/4.8/../../../../include/c++/4.8/i686-linux-gnu -internal-isystem /usr/bin/../lib/gcc/i686-linux-gnu/4.8/../../../../include/c++/4.8/backward -internal-isystem /usr/bin/../lib/gcc/i686-linux-gnu/4.8/../../../../include/i686-linux-gnu/c++/4.8 -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib/clang/3.4/include -internal-externc-isystem /usr/bin/../lib/gcc/i686-linux-gnu/4.8/include -internal-externc-isystem /usr/include/i386-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O3 -Woverloaded-virtual -Wcast-qual -W -Wall -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /home/danish/Desktop/Owl/llvm/llvm-3.4/lib/Transforms/SyncProf/testing/masstree-beta-master -ferror-limit 19 -fmessage-length 80 -fvisibility-inlines-hidden -mstackrealign -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp -load /home/danish/Desktop/Owl/llvm/llvm-3.4/Release+Asserts/lib/SkeletonPass.so -o test_atomics.o -x c++ test_atomics.cc
parser at end of file
Per-function optimization
Running pass 'Skeleton Pass' on function '#_Z9test_jsonv'
clang: error: unable to execute command: Segmentation fault (core dumped)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
Ubuntu clang version 3.4-1ubuntu3 (tags/RELEASE_34/final) (based on LLVM 3.4)
Target: i386-pc-linux-gnu
Thread model: posix
clang: note: diagnostic msg: PLEASE submit a bug report to http://bugs.debian.org/ and include the crash backtrace, preprocessed source, and associated run script.
clang: note: diagnostic msg:
PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /tmp/test_atomics-128b00.cpp
clang: note: diagnostic msg: /tmp/test_atomics-128b00.sh
clang: note: diagnostic msg:
make: *** [test_atomics.o] Error 254
This error appeared when I added the ->getName() part to retrieve the function names.
Help!
In reply to what Ismail Badawi suggested in the comments:
Yes, I think you were right! I added this null check and it worked:
Function *func = cast<CallInst>(&(*BI))->getCalledFunction();
if(func != NULL) errs() << func->getName();
Thank you #IsmailBadawi!
Is it possible to use the toolchain and sysroot from the Yocto SDK to cross compile with Clang/LLVM for ARM?
The environment-setup script within the Yocto SDK has the following compiler options:
export CC="arm-poky-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=hard -mfpu=neon -mtune=cortex-a7 --sysroot=$SDKTARGETSYSROOT"
I would like to cross compile this simple userspace application
testapp.c:
#include <stdio.h>
int main()
{
printf("Hello World\n");
return(0);
}
Following the guide http://clang.llvm.org/docs/CrossCompilation.html, I am trying to cross compile the app with
$ GCCFLAGS="-mcpu=cortex-a7 -mfpu=neon -mfloat-abi=hard"
$ GCCINCLUDE="/opt/poky/2.0.1/sysroots/cortexa7hf-vfp-neon-poky-linux-gnueabi/usr/include/c++/5.2.0/arm-poky-linux-gnueabi/
$ /usr/bin/clang -target arm-poky-linux-gnueabi $GCCFLAGS -I$GCCINCLUDE -ccc-gcc-name arm-poky-linux-gnueabi-gcc testapp.c -o testapp -v
However, this fails with
Ubuntu clang version 3.4.2-3ubuntu2~xedgers (tags/RELEASE_34/dot2-final) (based on LLVM 3.4.2)
Target: arm-poky-linux-gnueabi
Thread model: posix
Selected GCC installation:
"/usr/lib/llvm-3.4/bin/clang" -cc1 -triple armv7-poky-linux-gnueabi -S -disable-free -disable-llvm-verifier -main-file-name testapp.c -mrelocation-model static -mdisable-fp-elim -fmath-errno -mconstructor-aliases -target-cpu cortex-a7 -target-feature +neon -target-abi aapcs-linux -mfloat-abi hard -target-linker-version 2.24 -v -resource-dir /usr/lib/llvm-3.4/bin/../lib/clang/3.4.2 -I /opt/poky/2.0.1/sysroots/cortexa7hf-vfp-neon-poky-linux-gnueabi/usr/include/c++/5.2.0/arm-poky-linux-gnueabi/ -internal-isystem /usr/include/clang/3.4.2/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-3.4/bin/../lib/clang/3.4.2/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fno-dwarf-directory-asm -fdebug-compilation-dir /home/adtec/workspace/yocto/testapp -ferror-limit 19 -fmessage-length 207 -mstackrealign -fno-signed-char -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -vectorize-slp -o /tmp/testapp-8517af.s -x c testapp.c
clang -cc1 version 3.4.2 based upon LLVM 3.4.2 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
ignoring duplicate directory "/usr/include/clang/3.4.2/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/poky/2.0.1/sysroots/cortexa7hf-vfp-neon-poky-linux-gnueabi/usr/include/c++/5.2.0/arm-poky-linux-gnueabi
/usr/include/clang/3.4.2/include
/usr/local/include
/usr/include
End of search list.
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
'cortex-a7' is not a recognized processor for this target (ignoring processor)
"/usr/bin/as" -mfloat-abi=hard -mcpu=cortex-a7 -mfpu=neon -o /tmp/testapp-f4f688.o /tmp/testapp-8517af.s
/usr/bin/as: unrecognized option '-mfloat-abi=hard'
clang: error: assembler command failed with exit code 1 (use -v to see invocation)
What would be the appropriate Clang flags necessary to cross compile this simple application for ARM?
If you have access to a full build rather than just the SDK, you could try using the clang layer, https://github.com/kraj/meta-clang. Whilst it should be possible eventually to build an SDK containing clang I don't think anyone has done that yet.
you can use meta-clang and also generate a SDK which contains both gcc and clang based cross compilers, once SDK is installed there are CLANGCC and CLANGCXX environment variables available to invoke clang instead of gcc. if you want to use it as default you can do
export CC=${CLANGCC}
export CXX=${CLANGCXX}
export CPP=${CLANGCPP}
There is also a writeup for Clang SDK here
I have both clang and gcc installed on my Debian system. I wanted to try clang and gave
the following command. From the output it seems like clang is using lot more of gcc than
just the front end. How do I confirm that clang is actually using llvm-as, llvm-ld and
other llvm commands while compiling this simple program? I have installed most of llvm-*
commands. Thanks for any information.
clang -v c.c
Debian clang version 3.0-6 (tags/RELEASE_30/final) (based on LLVM 3.0)
Target: x86_64-pc-linux-gnu
Thread model: posix
"/usr/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free
-disable-llvm-verifier -main-file-name c.c -mrelocation-model static -mdisable-fp-elim
-masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-linker-
version 2.22 -momit-leaf-frame-pointer -v -resource-dir /usr/bin/../lib/clang/3.0
-fmodule-cache-path /var/tmp/clang-module-cache -internal-isystem /usr/local/include
-internal-isystem /usr/bin/../lib/clang/3.0/include -internal-externc-isystem
/usr/include/x86_64-linux-gnu -internal-externc-isystem /usr/include -ferror-limit 19
-fmessage-length 198 -fgnu-runtime -fobjc-runtime-has-arc -fobjc-runtime-has-weak
-fobjc-fragile-abi -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/c-MLrq5I.o -x
c c.c
clang -cc1 version 3.0 based upon llvm 3.0 hosted on x86_64-pc-linux-gnu
ignoring nonexistent directory "/usr/bin/../lib/clang/3.0/include"
ignoring nonexistent directory "/usr/bin/../lib/clang/3.0/include"
ignoring duplicate directory "/usr/local/include"
ignoring duplicate directory "/usr/include/x86_64-linux-gnu"
ignoring duplicate directory "/usr/include/x86_64-linux-gnu"
ignoring duplicate directory "/usr/include/x86_64-linux-gnu"
ignoring duplicate directory "/usr/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/include/x86_64-linux-gnu
/usr/include
/usr/include/clang/3.0/include/
/usr/lib/gcc/x86_64-linux-gnu/4.6/include/
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed/
End of search list.
"/usr/bin/ld" --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2
-o a.out /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o /usr/lib
/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-
gnu/4.6/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/4.6 -L/usr/lib/gcc/x86_64-linux-
gnu/4.6/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr
/lib/x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu
-L/usr/lib/gcc/x86_64-linux-gnu/4.6/../../.. -L/lib/x86_64-linux-gnu -L/lib -L/usr
/lib/x86_64-linux-gnu -L/usr/lib /tmp/c-MLrq5I.o -lgcc --as-needed -lgcc_s --no-as-
needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.6
/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crtn.o
You can pass -### to clang to see all programs it invokes. On most systems, clang links to the assembler library directly and calls it in-process in the cc1 process instead of shelling out to an external as program.