std::cout/std::cerr seg faults - c++

Question

#include <iostream>
#include <cstring>
#include <dlfcn.h>
#include <fcntl.h>
#include <X11/X.h>
#include <X11/Xlib.h>
void* Module = nullptr;
typedef int (*XNextEventPtr)(Display *display, XEvent *event_return);
XNextEventPtr XNextEventHook = nullptr;
extern "C" int XNextEvent(Display* display, XEvent* event_return)
{
if (event_return)
{
event_return->xany.send_event = false;
}
if (XNextEventHook)
{
return XNextEventHook(display, event_return);
}
return 0;
}
void __attribute__((constructor)) initialize() //DLLMain.
{
char Root[256] = {0};
strcat(Root, "/usr/lib");
#if defined(__x86_64__)
strcat(Root, "/x86_64-linux-gnu");
#else
strcat(Root, "/i386-linux-gnu");
#endif // defined
strcat(Root, "/libX11.so");
Module = dlopen(Root, RTLD_GLOBAL | RTLD_LAZY);
std::cout<<"Loaded"<<std::flush;
XNextEventHook = reinterpret_cast<XNextEventPtr>(dlsym(Module, "XNextEvent")); //some reason RTLD_NEXT didn't find it.
if (XNextEventHook)
{
std::cout<<"Found XNextEvent"<<std::flush;
}
}
void __attribute__((destructor)) deinitialize() //DLLMain.
{
if (Module)
{
dlclose(Module);
Module = nullptr;
}
}
Then I do:
LD_PRELOAD="~/Desktop/MyHook.so" /usr/lib64/firefox
and it will crash. However, it I replace std::cout and std::cerr with printf or perror, it works perfectly!
Is there a reason std::cout would crash the app?
It seems when I load the module using an application written in C++, it loads fine. But if I load the module with an application written in C, it crashes.
Ideas?

Answer 1

But if I load the module with an application written in C, it crashes.
The C application won't have code to call the initialization routines for the C++ library: streams such as std::cout will be uninitialised.
See the FAQ here, specifically:
• You must use your C++ compiler when compiling main() (e.g., for static initialization)