https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97771
--- Comment #5 from Erez Strauss <erstrauss at gmail dot com> --- Yes, thanks, the asm() works - but if it can be expressed in C++, why add the dependency on assembly? 1. attribute constructor - fails to compile 2. placing the address into the .init_array fails to generate the proper code. 3. assembly is required for gcc, but not for clang. I minimized the program by avoiding any include files, having three different macros for the different options. I would expect that gcc will handle correctly the first two options, as other compilers do. See https://godbolt.org/z/Mr1794 - for the three compilers: gcc clang icc ======================================== $ cat init_array_minimized.cpp extern "C" int write(int, const char *, long); extern "C" unsigned long strlen(const char *); extern "C" int snprintf(char *, unsigned long, const char *, ...); #define SIMPLE_LOCAL_FUNC_INIT_ARRAY() \ do \ { \ struct Local \ { \ static void init() \ { \ char buffer[256]; \ snprintf(buffer, sizeof(buffer), "%p: %s:%d: %s\n", (void*)&init, __FILE__, __LINE__, \ __PRETTY_FUNCTION__); \ write(1, buffer, strlen(buffer)); \ } \ }; \ static void *volatile initp __attribute__((__used__, section(".init_array"))){(void *)&Local::init}; \ } while (0) #define SIMPLE_LOCAL_FUNC_CONSTRUCTOR() \ do \ { \ struct Local \ { \ static void init() __attribute__((constructor)) \ { \ char buffer[256]; \ snprintf(buffer, sizeof(buffer), "%p: %s:%d: %s\n", (void*)&init, __FILE__, __LINE__, \ __PRETTY_FUNCTION__); \ write(1, buffer, strlen(buffer)); \ } \ }; \ } while (0) #define SIMPLE_LOCAL_FUNC_INIT_ASM() \ do \ { \ struct Local \ { \ static void init() \ { \ char buffer[256]; \ snprintf(buffer, sizeof(buffer), "%p: %s:%d: %s\n", (void*)&init, __FILE__, __LINE__, \ __PRETTY_FUNCTION__); \ write(1, buffer, strlen(buffer)); \ } \ }; \ __asm (".section .init_array, \"aw\",%%init_array; .balign %P0; .%P0byte %P1; .previous" : : "i" (sizeof (void *)), "g" ((void*)&Local::init)); \ } while (0) //#define LOCAL_INIT_FUNC() SIMPLE_LOCAL_FUNC_INIT_ARRAY() //#define LOCAL_INIT_FUNC() SIMPLE_LOCAL_FUNC_CONSTRUCTOR() #define LOCAL_INIT_FUNC() SIMPLE_LOCAL_FUNC_INIT_ASM() void funcA() { LOCAL_INIT_FUNC(); LOCAL_INIT_FUNC(); } inline void funcB() { LOCAL_INIT_FUNC(); } template<int> void funcT(int) { LOCAL_INIT_FUNC(); } int main() { write(1, "main\n", 5); funcA(); funcB(); funcT<0>(0); funcT<1>(0); return 0; } ================================== $ g++ -std=c++20 -O2 -fverbose-asm --save-temps -o init_array_minimized init_array_minimized.cpp $ ./init_array_minimized 0x4011e0: init_array_minimized.cpp:63: static void funcA()::Local::init() 0x401180: init_array_minimized.cpp:64: static void funcA()::Local::init() 0x401250: init_array_minimized.cpp:67: static void funcB()::Local::init() 0x4012b0: init_array_minimized.cpp:69: static void funcT(int)::Local::init() [with int <anonymous> = 0] 0x401310: init_array_minimized.cpp:69: static void funcT(int)::Local::init() [with int <anonymous> = 1] main