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The Affect of Library Initialization Failure on Whether Module Destruction Occurs

We test if the destructor of a Windows library that failed initialization will run.

Result

DllMain: DLL_PROCESS_ATTACH
DllMain: DLL_PROCESS_DETACH

Yes, the destructor of a library that failed initialization will run. This behavior is incongruent to how every programming language and foreseeably system that implements failable constructors.

The Windows library loader will run the library's DLL_PROCESS_DETACH directly after its DLL_PROCESS_ATTACH if the latter fails:

dll_test!DllMain+0x37:
00007ff8`76001037 cc              int     3
0:000> k
 # Child-SP          RetAddr               Call Site
00 00000023`ecdaf070 00007ff8`760012f3     dll_test!DllMain+0x37 [C:\Users\user\Documents\QubesIncoming\lab-projects\library-init-fail-detach-routine\dll-test.c @ 9] 
01 00000023`ecdaf0b0 00007ff8`7b8e9a1d     dll_test!dllmain_dispatch+0x8f [d:\a01\_work\20\s\src\vctools\crt\vcstartup\src\startup\dll_dllmain.cpp @ 281] 
02 00000023`ecdaf110 00007ff8`7b93d2f7     ntdll!LdrpCallInitRoutine+0x61
03 00000023`ecdaf180 00007ff8`7b93d08a     ntdll!LdrpInitializeNode+0x1d3
04 00000023`ecdaf2d0 00007ff8`7b93d110     ntdll!LdrpInitializeGraphRecurse+0x42
05 00000023`ecdaf310 00007ff8`7b9a3cb2     ntdll!LdrpInitializeGraphRecurse+0xc8
06 00000023`ecdaf350 00007ff8`7b945deb     ntdll!LdrpInitializeProcess+0x1f62
07 00000023`ecdaf770 00007ff8`7b945c73     ntdll!LdrpInitialize+0x15f
08 00000023`ecdaf810 00007ff8`7b945c1e     ntdll!LdrpInitialize+0x3b
09 00000023`ecdaf840 00000000`00000000     ntdll!LdrInitializeThunk+0xe
0:000> g
(1878.1684): Break instruction exception - code 80000003 (first chance)
dll_test!DllMain+0x4b:
00007ff8`7600104b cc              int     3
0:000> k
 # Child-SP          RetAddr               Call Site
00 00000023`ecdaf070 00007ff8`7600130f     dll_test!DllMain+0x4b [C:\Users\user\Documents\QubesIncoming\lab-projects\library-init-fail-detach-routine\dll-test.c @ 15] 
01 00000023`ecdaf0b0 00007ff8`7b8e9a1d     dll_test!dllmain_dispatch+0xab [d:\a01\_work\20\s\src\vctools\crt\vcstartup\src\startup\dll_dllmain.cpp @ 287] 
02 00000023`ecdaf110 00007ff8`7b93d2f7     ntdll!LdrpCallInitRoutine+0x61
03 00000023`ecdaf180 00007ff8`7b93d08a     ntdll!LdrpInitializeNode+0x1d3
04 00000023`ecdaf2d0 00007ff8`7b93d110     ntdll!LdrpInitializeGraphRecurse+0x42
05 00000023`ecdaf310 00007ff8`7b9a3cb2     ntdll!LdrpInitializeGraphRecurse+0xc8
06 00000023`ecdaf350 00007ff8`7b945deb     ntdll!LdrpInitializeProcess+0x1f62
07 00000023`ecdaf770 00007ff8`7b945c73     ntdll!LdrpInitialize+0x15f
08 00000023`ecdaf810 00007ff8`7b945c1e     ntdll!LdrpInitialize+0x3b
09 00000023`ecdaf840 00000000`00000000     ntdll!LdrInitializeThunk+0xe

Hypothetical: The Opposite Result

If Windows implemented the library loader's reponse to a failing library initialization correctly, then the below code sample demonstrates what doing properly programmed resource initialization with DllMain could look like.

For handling an error mid-initialization with multiple resource allocations, it would be acceptable to back out by doing some centeralized cleanup with goto, freeing only the prior successful resource allocations in reverse order before returning a failed module initialization:

// WARNING: Hypothical code. Not correct for practical use.

LPVOID alloc1;
LPVOID alloc2;
LPVOID alloc3;

BOOL WINAPI DllMain(HINSTANCE hinstDll, DWORD fdwReason, LPVOID lpvReserved)
{
    switch (fdwReason)
    {
    case DLL_PROCESS_ATTACH:
        alloc1 = HeapAlloc(GetProcessHeap(), 0, 1024);
        if (alloc1 == NULL) return FALSE;
        alloc2 = HeapAlloc(GetProcessHeap(), 0, 1024);
        if (alloc2 == NULL) goto cleanup_and_fail_1;
        alloc3 = HeapAlloc(GetProcessHeap(), 0, 1024);
        if (alloc3 == NULL) goto cleanup_and_fail_2;
        return TRUE;

        // Cleanup and fail early
        cleanup_and_fail_2:
            HeapFree(GetProcessHeap(), 0, alloc2);
        cleanup_and_fail_1:
            HeapFree(GetProcessHeap(), 0, alloc1);
        return FALSE;

        break;
    case DLL_PROCESS_DETACH:
        HeapFree(GetProcessHeap(), 0, alloc1);
        HeapFree(GetProcessHeap(), 0, alloc2);
        HeapFree(GetProcessHeap(), 0, alloc3);
        break;
    }

    return TRUE;
}