Changes between Version 5 and Version 6 of AppLibraries

Timestamp:

Sep 23, 2011, 9:32:56 AM (14 years ago)

Author:

davea

Comment:

--

AppLibraries

@@ -1 +1 @@
 = Dynamic library issues =
 
-Applications can use dynamic libraries;
-just include them in the [UpdateVersions#multifile multi-file application].
+Suppose your application uses a dynamic library, say '''vcomp90.dll'''.
+Recall that [BoincFiles BOINC files are immutable].
+Hence there is a problem if either
 
-A problem arises if you support multiple platforms
-and the libraries for the different platforms have the same name.
-In BOINC, if files are called the same, they must be the same file.
+ * You support multiple platforms (say, Win32 and Win64),
+   and there are different versions of '''vcomp90.dll''' for each platform.
+ * You need to update to new versions of the library.
 
-For example, suppose you support both Win32 and Win64,
-and you use a DLL "vcomp90.dll" that has 32- and 64-bit versions.
-If you install the 32-bit app first,
-it will end up trying to link the 64-bit library, and will crash.
+One solution is to give the libraries names that encode the
+platform and version number,
+e.g. '''vcomp90_win32_1_17.dll''' and '''vcomp90_win64_1_17.dll'''.
+However, this may be infeasible
+because the name '''vcomp90.dll''' is embedded in your Makefiles and
+would be difficult to change.
 
-One solution is to give the libraries different names,
-e.g. '''vcomp90_32.dll''' and '''vcomp90_64.dll'''.
-However, this requires changing your application (or build system)
-to look for the DLL under that different name.
+A second solution, which doesn't require changing Makefiles,
+is to give the libraries different physical names but the same logical name.
+To do this, use something like the following in your
+[AppVersionNew#Theversiondescriptionfile version description file]:
+{{{
+...
+  <file>
+    <physical_name>vcomp90_win32_1_17.dll</physical_name>
+    <logical_name>vcomp90.dll</logical_name>
+    <copy_file/>
+...
+}}}
 
-A second solution, which doesn't require changing Makefiles or VS project files,
-is to give the libraries different physical names but the same logical name.
-Do this as follows:
-
- * In the 32-bit app, call the file '''vcomp90.dll=vcomp90_v1.0_32bit.dll'''. This will be copied as "vcomp90_v1.0_32bit.dll" to the download directory, and  used as "vcomp90.dll" on the client.
-
- * Then, add another file called '''vcomp90.dll=vcomp90_v1.0_32bit.dll.file_ref_info''' containing just:
-{{{
-<copy_file/>
-}}}
-copy_file will ensure the file is '''copied to''' '''vcomp90.dll''', instead of linked, 
-since Windows obviously won't understand BOINC soft links when trying to find 
-the DLL.
-
-It's a good idea to add a version number to the physical name,
-in case you ever need to modify the file.
-This also means that even if you don't use multiple platforms,
-it's still useful to use this technique,
-using just a version number and no platform name.
+The '''copy_file''' flag tells the BOINC to copy the library to
+the application's runtime directory.