I have two implementations of the same behavior that I believe should produce the same results but are instead producing different results. When compiled in Go using cgo , I get a different symbol address resolution than when compiled in C. I would like to understand why.

I reduced the problem to a couple of small examples, one in C and one in Go. I tested these in an Ubuntu 18 Docker container running on my Mac laptop.

test.c:

// gcc test.c -D_GNU_SOURCE -ldl // Output: Real: 0x7fd05559d7d0 Current: 0x7fd05559d7d0 #include <dlfcn.h> #include <stdio.h> int main() { void * fd = dlopen("libc.so.6", RTLD_LAZY); void * real_sym = dlsym(fd, "accept"); void * curr_sym = dlsym(RTLD_NEXT, "accept"); printf("Real: %p Current: %p

", real_sym, curr_sym); return 0; }

test.go:

// go build test.go // Output: Real: 0x7f264583b7d0 Current: 0x7f2645b1b690 package main // #cgo CFLAGS: -D_GNU_SOURCE // #cgo LDFLAGS: -ldl // #include <dlfcn.h> import "C" import "fmt" func main() { fp := C.dlopen(C.CString("libc.so.6"), C.RTLD_LAZY) real_sym := C.dlsym(fp, C.CString("accept")) curr_sym := C.dlsym(C.RTLD_NEXT, C.CString("accept")) fmt.Printf("Real: %p Current: %p

", real_sym, curr_sym) }

I get the output of Real: 0x7fd05559d7d0 Current: 0x7fd05559d7d0 when test.c gets compiled ( gcc test.c -D_GNU_SOURCE -ldl ). However, when I build test.go I see Real: 0x7f264583b7d0 Current: 0x7f2645b1b690 .

I assume that go is wrapping some symbols itself, but I would like to know exactly what's happening. Thanks!

A couple of extra pieces after seeing some of the initial comments. I changed test.c as below and then ran in a loop ( while [ 1 ]; do ./a.out; done ). It's consistently getting equal addresses for me (different each run, though).

// gcc test.c -D_GNU_SOURCE -ldl // Output: Real: 0x7fd05559d7d0 Current: 0x7fd05559d7d0 #include <dlfcn.h> #include <stdio.h> int main() { void * fd = dlopen("libc.so.6", RTLD_LAZY); void * real_sym = dlsym(fd, "accept"); void * curr_sym = dlsym(RTLD_NEXT, "accept"); if(real_sym != curr_sym) { printf("Real: %p Current: %p

", real_sym, curr_sym); } return 0; }

I also tried a modification of the Go code to check if it had to do with how Go called out to C, but that still did not have the addresses match:

// go build dos.go // Output: Real: 0x7f264583b7d0 Current: 0x7f2645b1b690 package main // #cgo CFLAGS: -D_GNU_SOURCE // #cgo LDFLAGS: -ldl // #include <dlfcn.h> // #include <stdio.h> // int doit() { // void * fd = dlopen("libc.so.6", RTLD_LAZY); // void * real_sym = dlsym(fd, "accept"); // void * curr_sym = dlsym(RTLD_NEXT, "accept"); // printf("Real: %p Current: %p

", real_sym, curr_sym); // return 0; // } import "C" func main() { C.doit() }