Open Radar

 
Summary:
It appears that -ObjC causes the linker to link all LTO objects in all archives. If -dead_strip is also passed the linker can fail to link the program, producing "loaded too late" and "undefined symbol" errors in certain cases. 

See also: https://llvm.org/bugs/show_bug.cgi?id=23007

Steps to Reproduce:
With Xcode installed:

$ cat main.cc
int main() {}
$ cat globalinit.cc
class A {
public:
  A();
};
A a;
int b;
$ cat ctor.cc
#include <stdio.h>
class A {
public:
  A();
};
A::A() {
  puts("hello world");
} 
$ clang++ -c -flto main.cc globalinit.cc
$ clang++ -c ctor.cc
$ rm -f libglobalinit.a
$ ar cru libglobalinit.a globalinit.o
$ rm -f libctor.a
$ ar cru libctor.a ctor.o
$ clang++ -Wl,-ObjC -o test1 main.o libglobalinit.a libctor.a
$ clang++ -Wl,-ObjC -Wl,-dead_strip -o test2 main.o libglobalinit.a libctor.a
ld: warning: '_b' is implemented in bitcode, but it was loaded too late
Undefined symbols for architecture x86_64:
  "_a", referenced from:
      __GLOBAL__I_a in lto.o
      import-atom in libglobalinit.a(globalinit.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
$ ./test1
hello world

Expected Results:
test1 should print no output and test2 should link successfully.

Actual Results:
The global initializers in test1 are run causing the output "hello world" to be printed. test2 produces linker errors.

Version:
OS X 10.9.5
Xcode 6.1.1