OpenEuphoria

Finding DLL files (Interpreter vs .EXE)

• Posted by marky1124 <mark_young at hotmail??om> Apr 18, 2008
• 546 views

Hi,

I have discovered that the way in which .dlls are found and loaded changes if I
am running my code through the Euphoria interpreter or bound as an EXE.

My code does open_dll("libcurl.dll"). libcurl.dll depends on libeay32.dll and
libssl32.dll. All three .dlls are in the current directory from which I run these
test. There is an older version of libeay32.dll in c:\windows\system32 (I'm using
XP). I am using sysinternals filemon to monitor attempts to access the lib*.dll
files.

If I run the code as "exw test.exw" then I can see EXW.EXE look for libcurl.dll
in the following locations in this order:
	C:\EUPHORIA\BIN\libcurl.dll		- NOT FOUND
	C:\WINDOWS\system32\libcurl.dll		- NOT FOUND
	C:\WINDOWS\system\libcurl.dll		- NOT FOUND
	C:\WINDOWS\libcurl.dll			- NOT FOUND
	C:\my_development_directory\libcurl.dll	- FOUND

When it reads in libcurl.dll it moves on to locate the dlls that libcurl.dll
requires, here's where it looks

	C:\EUPHORIA\BIN\libeay32.dll		- NOT FOUND
	C:\WINDOWS\system32\libeay32.dll	- FOUND

It then fails because it's found an old libeay32.dll which is incompatible,
it hasn't looked in my development directory where the correct version is
waiting to be used.


If I now bindw test.exw into test.exe and run then the behaviour is different.
It looks in the current directory first for the .dlls and given that it finds
them it looks no further. If the .dll is not in the current directory then it
goes on to look further in this order:

	C:\my_development_directory\libcurl.dll	- NOT FOUND
	C:\WINDOWS\system32\libcurl.dll		- NOT FOUND
	C:\WINDOWS\system\libcurl.dll		- NOT FOUND
	C:\WINDOWS\libcurl.dll			- NOT FOUND

	
I am completely new to Windows development and DLL handling. Finding out the
above caused me a fair amount of confusion, so I thought I'd share my
experience here and also put it out for comment - Is the Euphoria interpreter
doing the right thing in the way it handles DLL searches compared to the bound
version of the same code? At the very least it confused me as a new developer,
especially since the error I encountered said "Can't find libcurl.dll" when in
fact the real issue was an incompatible libeay32.dll in c:\windows\system32.

Thanks very much for your attention,
Cheers,
Mark