CODEWITHSUNDEEP
dllwindows-7environment-variables
Luís Guilherme
Luís Guilherme

Reputation: 2709

DLL search on windows

On linux, we have LIBRARY_PATH and LD_LIBRARY_PATH environment variables in order for programs to search for libraries. Do we have similar thing on windows? Particularly Windows 7?

Also, I would like to know best practices for DLL use (where to put them, use envs or not, etc.), since I want to work on windows like everyone does, and not to sloth myself on workarounds :)

Upvotes: 19

Views: 28178

Answers (4)

TonySalimi
TonySalimi

Reputation: 8427

According to what @andrew has mentioned in his answer, the order of folders that are used on Windows to search a DLL may be different from one configuration to another. I think the simplest way to check this order on Windows is to use the Dependency Walker tool. After opening the tool, and pressing the "Configure Module Search Order" button on the toolbar, you will see a window like this:

enter image description here

This window shows you the current search order on your machine. The interesting part is that by pressing "Expand", you can see the whole folders in the search path one by one. You may also change the order if you want, to be used for loading an specific module.

Upvotes: 0

Andrew Bainbridge
Andrew Bainbridge

Reputation: 4808

Edit: As explained by Bob, this answer describes the Alternate Search Order, which is not what most applications would see. The full rules are quite complex. I don't think I can summarize them here. Instead, read the Microsoft docs - https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-search-order

My original answer was:

This MSDN article explains the default search order. I quote:

  1. The directory specified by lpFileName.
  2. The system directory. Use the GetSystemDirectory function to get the path of this directory.
  3. The 16-bit system directory. There is no function that obtains the path of this directory, but it is searched.
  4. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
  5. The current directory.
  6. The directories that are listed in the PATH environment variable. Note that this does not include the per-application path specified by the App Paths registry key. The App Paths key is not used when computing the DLL search path.

In (1), if you statically linked against the DLL's stub library, I think "the directory specified by lpFileName" is the process's exe's path.

Upvotes: 18

Luca Rocchi
Luca Rocchi

Reputation: 6464

It looks on currentDir first then WinDir and SystemDir also in your path

Upvotes: 0

anon
anon

Reputation:

Take a look at the help for the LoadLibrary and CreateProcess functions. These describe the paths used to locate DLLs, and how you can modify them.

Upvotes: 2

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