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Kaleb Barrett
Kaleb Barrett

Reputation: 1594

Runtime-load A DLL In The Same Directory (Not The Application Directory)

I have a situation where I need to load a DLL (libcocotb.dll) at runtime (using LoadLibrary) from another DLL (libembed.dll) that exists in the same directory. These DLLs are not in the same directory as the application.

> tree
.
├── ...
├── libcocotb.dll
└── libembed.dll

Specifying just the library name LoadLibrary("libcocotb.dll"), did not find the library. LoadLibrary(".\\libcocotb.dll"), did not find the library. Adding the directory to the PATH seems like the wrong answer, and I would need to determine the location of the directory at runtime since the binaries need to be relocatable (they are going in a Python wheel at the end of the day).

On Linux, I can just add $ORIGIN to the RPATH of the loading DLL. Is there nothing similar on Windows? I am not very familiar with Windows loader and library system.

Upvotes: 1

Views: 694

Answers (1)

dxiv
dxiv

Reputation: 17638

One way to do it in Windows is:

  • save the HMODULE of libembed.dll when it gets loaded, which is passed as the first argument to its DllMain entry point;

  • later, when preparing to load the other DLL, use GetModuleFileName with the saved HMODULE to get the full path to libembed.dll;

  • split the libembed.dll filename off the full path, using for example the PathRemoveFileSpec API or the _splitpath CRT function;

  • combine the resulting directory path with the libcocotb.dll filename to build the full path to the other DLL, using for example PathCombine or _makepath;

  • use the full path to libcocotb.dll to LoadLibrary the DLL.

Upvotes: 2

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