gcc

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

LD_LIBRARY_PATH vs LIBRARY_PATH

LIBRARY_PATH is used by gcc before compilation to search directories containing static and shared libraries that need to be linked to your program. LD_LIBRARY_PATH is used by your program to search directories containing shared libraries after it has been successfully compiled and linked. EDIT: As pointed below, your libraries can be static or shared. If … Read more

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

Why doesn’t gcc resolve _mm256_loadu_pd as single vmovupd?

GCC’s default tuning (-mtune=generic) includes -mavx256-split-unaligned-load and -mavx256-split-unaligned-store, because that gives a minor speedup on some CPUs (e.g. first-gen Sandybridge, and some AMD CPUs) in some cases when memory is actually misaligned at runtime. Use -O3 -mno-avx256-split-unaligned-load -mno-avx256-split-unaligned-store if you don’t want this, or better, use -mtune=haswell. Or use -march=native to optimize for your own … Read more

What is the -fPIE option for position-independent executables in gcc and ld?

PIE is to support address space layout randomization (ASLR) in executable files. Before the PIE mode was created, the program’s executable could not be placed at a random address in memory, only position independent code (PIC) dynamic libraries could be relocated to a random offset. It works very much like what PIC does for dynamic … Read more