On 15 April 2010 05:25, Gordon Schumacher <[email protected]> wrote: > Now let's pretend that a user has installed my WhizBangShellExt, but > unbeknownst to me he's previously loaded CrustyExplorer, another shell > extension. It also depends on libFoo.dll, but it's a much older > application and is no longer supported, so it's installed libFoo 2.718 - > and it's even a different major revision, and therefore has a different API. > > My understanding is that for a given process, there can only be one > "libFoo.dll" loaded at a time; if Explorer loads CrustyExplorer.dll > first, it'll get libFoo 2.718, and if it loads WhizBangShellExt.dll > first, it'll get libFoo 3.141 - which needless to say is rather less > than ideal!
I do believe this is a problem, but I too am not 100% sure how it plays out in reality. What it all boils down to is what symbols the DLLs export, and how the dynamic linker on Windows performs symbol resolution. I know that on Linux, if a binary needs to call function "foo", and there is something already loaded which exports symbol "foo", that will be used - which is precisely why things like LD_PRELOAD work for intercepting library calls. My gut feeling would be that the Windows linker isn't entirely dissimilar, since there are only a handful of sensible ways to solve the problem. If CrustyExplorer is open-source, the correct solution is to either port it to the newer libFoo API, or - worst solution, least effort - statically link it against the old libFoo, ensuring that the resulting DLL doesn't export any libFoo symbols. If it's closed-source you may be out of luck, unless tools exist for somehow re-linking existing binaries, allowing static linking to be performed after the fact. Note that if libFoo is a well-designed library, it may have some initialisation/version-checking functions that WhizBangShellExt can use to detect the problem at run-time. Corrections (and explanations of the symbol resolution strategy on Windows) much appreciated. :) Regards, Phil _______________________________________________ Mailing list: https://launchpad.net/~coapp-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~coapp-developers More help : https://help.launchpad.net/ListHelp
