Calling dlopen with RTLD_GLOBAL flag set results in segfault when it's called from a non-base namespace. This is due to the fact that add_to_global_resize does not take into account the global namespace does not exist yet. The following code reproduces the issue. -------------- docker run --rm -it ubuntu:devel bash apt-get update apt install g++-10 cd ~ cat >a.cpp <<EOF // a.cpp #include <iostream> #include <dlfcn.h> using namespace std; int main () { void * handle = nullptr; bool mopen = true; if (mopen) { cout << "mopening libb.so" << endl; handle = dlmopen(LM_ID_NEWLM, "libb.so", RTLD_NOW | RTLD_LOCAL); } else { cout << "opening libb.so" << endl; handle = dlopen("libb.so", RTLD_NOW | RTLD_LOCAL); } void (*bfunc)(); *(void**)(&bfunc) = dlsym(handle, "bfunc"); bfunc(); return 0; } EOF cat >b.cpp <<EOF // b.cpp #include <iostream> #include <dlfcn.h> using namespace std; extern "C" void bfunc() { cout << "bfunc in b.cpp is being called..." << endl; void * handle = dlopen("libc.so", RTLD_NOW | RTLD_GLOBAL); //void * handle = dlopen("libc.so", RTLD_NOW | RTLD_LOCAL); void (*cfunc)(); *(void**)(&cfunc) = dlsym(handle, "cfunc"); cfunc(); } EOF cat >c.cpp <<EOF // c.cpp #include <iostream> using namespace std; extern "C" void cfunc() { cout << "cfunc in c.cpp is being called..." << endl; } EOF g++-10 a.cpp -o a -ldl -Wl,-rpath `pwd` g++-10 b.cpp -o libb.so -shared -fPIC -ldl -Wl,-rpath `pwd` g++-10 c.cpp -o libc.so -shared -fPIC -------------- Finally, when running LD_DEBUG=all ./a, it crashes with the following log: -------------- 902: symbol=_ZNSt8ios_base4InitD1Ev; lookup in file=/root/libb.so [1] 902: symbol=_ZNSt8ios_base4InitD1Ev; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__cxa_finalize; lookup in file=/root/libb.so [1] 902: symbol=__cxa_finalize; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__cxa_finalize; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1] 902: symbol=_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc; lookup in file=/root/libb.so [1] 902: symbol=_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=_ZNSolsEPFRSoS_E; lookup in file=/root/libb.so [1] 902: symbol=_ZNSolsEPFRSoS_E; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__cxa_atexit; lookup in file=/root/libb.so [1] 902: symbol=__cxa_atexit; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__cxa_atexit; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1] 902: symbol=_ZNSt8ios_base4InitC1Ev; lookup in file=/root/libb.so [1] 902: symbol=_ZNSt8ios_base4InitC1Ev; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/root/libb.so [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/ld-linux-aarch64.so.1 [0] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libm.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libgcc_s.so.1 [1] 902: symbol=__gmon_start__; lookup in file=/root/libc.so [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libstdc++.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libc.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libm.so.6 [1] 902: symbol=__gmon_start__; lookup in file=/lib/ld-linux-aarch64.so.1 [0] 902: symbol=__gmon_start__; lookup in file=/lib/aarch64-linux-gnu/libgcc_s.so.1 [1] Segmentation fault -------------- LIBC version: -------------- $ ldd --version ldd (Ubuntu GLIBC 2.36-0ubuntu4) 2.36 Copyright (C) 2022 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Written by Roland McGrath and Ulrich Drepper -------------- The error won’t happen if I dlopen with RTLD_LOCAL in b.cpp rather than RTLD_GLOBAL. I would appreciate any help on what I’m doing wrong here. Best, Nima