How to see which flags -march=native will activate?
You can use the -Q –help=target options: gcc -march=native -Q –help=target … The -v option may also be of use. You can see the documentation on the –help option here.
gcc
How to generate gcc debug symbol outside the build target?
You need to use objcopy to separate the debug information: objcopy –only-keep-debug “${tostripfile}” “${debugdir}/${debugfile}” strip –strip-debug –strip-unneeded “${tostripfile}” objcopy –add-gnu-debuglink=”${debugdir}/${debugfile}” “${tostripfile}” I use the bash script below to separate the debug information into files with a .debug extension in a .debug directory. This way I can tar the libraries and executables in one tar file … Read more
Disable all gcc warnings
-w is the GCC-wide option to disable warning messages.
libpthread.so.0: error adding symbols: DSO missing from command line
You should mention the library on the command line after the object files being compiled: gcc -Wstrict-prototypes -Wall -Wno-sign-compare -Wpointer-arith -Wdeclaration-after-statement -Wformat-security -Wswitch-enum -Wunused-parameter -Wstrict-aliasing -Wbad-function-cast -Wcast-align -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers -Wno-override-init \ -g -O2 -export-dynamic -o utilities/ovs-dpctl utilities/ovs-dpctl.o \ lib/libopenvswitch.a \ /home/jyyoo/src/dpdk/build/lib/librte_eal.a /home/jyyoo/src/dpdk/build/lib/libethdev.a /home/jyyoo/src/dpdk/build/lib/librte_cmdline.a /home/jyyoo/src/dpdk/build/lib/librte_hash.a /home/jyyoo/src/dpdk/build/lib/librte_lpm.a /home/jyyoo/src/dpdk/build/lib/librte_mbuf.a /home/jyyoo/src/dpdk/build/lib/librte_ring.a /home/jyyoo/src/dpdk/build/lib/librte_mempool.a /home/jyyoo/src/dpdk/build/lib/librte_malloc.a \ -lrt -lm -lpthread … Read more
GCC dump preprocessor defines
Yes, use -E -dM options instead of -c. Example (outputs them to stdout): echo | gcc -dM -E – echo | clang -dM -E – For C++ echo | g++ -dM -E -x c++ – echo | clang++ -dM -E -x c++ – From the gcc manual: Instead of the normal output, generate a list … Read more
I don’t understand -Wl,-rpath -Wl,
The -Wl,xxx option for gcc passes a comma-separated list of tokens as a space-separated list of arguments to the linker. So gcc -Wl,aaa,bbb,ccc eventually becomes a linker call ld aaa bbb ccc In your case, you want to say “ld -rpath .“, so you pass this to gcc as -Wl,-rpath,. Alternatively, you can specify repeat … Read more
How do I force make/GCC to show me the commands?
To invoke a dry run: make -n This will show what make is attempting to do.
gcc makefile error: “No rule to make target …”
That’s usually because you don’t have a file called vertex.cpp available to make. Check that: that file exists. you’re in the right directory when you make. Other than that, I’ve not much else to suggest. Perhaps you could give us a directory listing of that directory.
What exactly is LLVM?
LLVM is a library that is used to construct, optimize and produce intermediate and/or binary machine code. LLVM can be used as a compiler framework, where you provide the “front end” (parser and lexer) and the “back end” (code that converts LLVM’s representation to actual machine code). LLVM can also act as a JIT compiler … Read more
Why does the order in which libraries are linked sometimes cause errors in GCC?
(See the history on this answer to get the more elaborate text, but I now think it’s easier for the reader to see real command lines). Common files shared by all below commands $ cat a.cpp extern int a; int main() { return a; } $ cat b.cpp extern int b; int a = b; … Read more