Basics

Sometimes a Windows-Library (*.dll or *.pyd) can not be loaded, because some other libraries are missing. Then the error "ImportError: DLL load failed" is shown. A Windows-Library (or Windows-Program) can load other Windows-Library dynamically (with LoadLibraryA/W from kernel32.dll) or statically with the PE import directory table.

For static linked libraries windows will only show an error message, but no further information (eg. which library could not be loaded).

The Idea of the program is:

1. Load the Library with win32api.LoadLibrary and check if it can be loaded:
   1. If it was loaded --> finish
   2. If it was not loaded -->
      1. Loop through all static referenced libraries in the import directories of the library and try loading them indiviually (start at the beginning)

Usage

If you want to inspect a library, then run:

python checkdll <path_to_dll> [--full_inspect]

Example (1)

Call:

python checkdll "cudnn_adv_infer64_8.dll" --full_inspect

Output:

Handle (0x7ffa1b0d0000): api-ms-win-core-rtlsupport-l1-1-0.dll in 'C:\Windows\SYSTEM32'
Handle (0x7ffa18760000): KERNELBASE.dll in 'C:\Windows\System32'
Handle (0x7ffa19540000): KERNEL32.dll in 'C:\Windows\System32'
Handle (0x7ff927b30000): cudnn_ops_infer64_8.dll in 'C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.8\bin'
Handle (0x7ff8b9a30000): cudnn_adv_infer64_8.dll in 'C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.8\bin'
Errors detected: 0

Example (2)

Call:

python checkdll "gpujpeg.cp39-win_amd64.pyd" --full_inspect

gpujpeg.cp39-win_amd64.pyd loads gpujpeg.dll, which was missing:

Output:

Handle (NONE): gpujpeg.dll
Handle (0x7ffa1b0d0000): ntdll.dll in 'C:\Windows\SYSTEM32'
Handle (0x7ffa18760000): api-ms-win-core-console-l1-1-0.dll in 'C:\Windows\System32'
Handle (0x7ffa19540000): api-ms-win-core-processthreads-l1-1-0.dll in 'C:\Windows\System32'
Handle (0x7ffa19490000): msvcrt.dll in 'C:\Windows\System32'
Handle (0x7ffa0f0e0000): VERSION.dll in 'C:\Windows\SYSTEM32'
Handle (0x7ffa19820000): RPCRT4.dll in 'C:\Windows\System32'
Handle (0x7ffa19070000): WS2_32.dll in 'C:\Windows\System32'
Handle (0x7ffa18b40000): bcrypt.dll in 'C:\Windows\System32'
Handle (0x7ffa1a520000): api-ms-win-eventing-controller-l1-1-0.dll in 'C:\Windows\System32'
Handle (0x7ffa19740000): ADVAPI32.dll in 'C:\Windows\System32'
Handle (0x7ffa18520000): api-ms-win-crt-runtime-l1-1-0.dll in 'C:\Windows\System32'
Handle (0x7ffa0b240000): VCRUNTIME140.dll in 'C:\Users\xxxx\AppData\Local\Programs\Python\Python39'
Handle (0x7ff9cf460000): python39.dll in 'C:\Users\xxxx\AppData\Local\Programs\Python\Python39'
Handle (0x7ff9fdea0000): VCRUNTIME140_1.dll in 'C:\Users\xxxx\AppData\Local\Programs\Python\Python39'
Handle (NONE): gpujpeg.cp39-win_amd64.pyd
Errors detected: 2

Fix:

Add the directory containing the gpujpeg.dll to python:

import os
os.add_dll_library("path to gpujpeg.dll")

or add this directory to the windows environent variable PATH.