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Use get_instance_handle() over GetModuleHandle(NULL) #1446

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Use get_instance_handle() over GetModuleHandle(NULL) #1446

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20 changes: 18 additions & 2 deletions glutin/src/api/wgl/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ use winapi::shared::ntdef::LPCWSTR;
use winapi::shared::windef::{HDC, HGLRC, HWND};
use winapi::um::libloaderapi::*;
use winapi::um::wingdi::*;
use winapi::um::winnt::IMAGE_DOS_HEADER;
use winapi::um::winuser::*;

use std::ffi::{CStr, CString, OsStr};
Expand Down Expand Up @@ -772,7 +773,7 @@ unsafe fn load_extra_functions(win: HWND) -> Result<gl::wgl_extra::Wgl, Creation
}

// access to class information of the real window
let instance = GetModuleHandleW(std::ptr::null());
let instance = get_instance_handle();
let mut class: WNDCLASSEXW = std::mem::zeroed();

if GetClassInfoExW(instance, class_name.as_ptr(), &mut class) == 0 {
Expand Down Expand Up @@ -814,7 +815,7 @@ unsafe fn load_extra_functions(win: HWND) -> Result<gl::wgl_extra::Wgl, Creation
rect.bottom - rect.top,
std::ptr::null_mut(),
std::ptr::null_mut(),
GetModuleHandleW(std::ptr::null()),
get_instance_handle(),
std::ptr::null_mut(),
);

Expand Down Expand Up @@ -896,3 +897,18 @@ fn choose_dummy_pixel_format(hdc: HDC) -> Result<raw::c_int, CreationError> {

Ok(pf_id)
}

fn get_instance_handle() -> HINSTANCE {
// Gets the instance handle by taking the address of the
// pseudo-variable created by the Microsoft linker:
// https://devblogs.microsoft.com/oldnewthing/20041025-00/?p=37483

// This is preferred over GetModuleHandle(NULL) because it also works in DLLs:
// https://stackoverflow.com/questions/21718027/getmodulehandlenull-vs-hinstance

extern "C" {
static __ImageBase: IMAGE_DOS_HEADER;
}

unsafe { &__ImageBase as *const _ as _ }
}