Differences

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--- developingpld:advanceddeveloping:fixingasneeded [2006-08-08 15:42] – - typo SamChi
+++ developingpld:advanceddeveloping:fixingasneeded [2007-05-27 20:51] (current) – arekm
@@ Line 4: / Line 4: @@
-==== Quick Workaround ====
+===== Quick and ugly workaround (DON'T USE IT!) =====
-Put in spec file this line:
+Put this line in ''spec'' file:
 <file>%define filterout_ld -Wl,--as-needed
 </file>
-But **don't use it** unless you really need.
+But **don't use it** unless you really need to quickly build a package. Never ever try to commit such a change. It might be tempting to do so but if you think about it ''--as-needed'' did it's job well and disabled unneeded libraries. If building fails, it's the package that needs to get fixed, not the linker flags.
-Why ? Because it's very stupid. If something fails to build normally it's a sign ''--as-needed'' did well it's job and disabled unneeded libraries.
@@ Line 20: / Line 20: @@
-== About positions ==
+==== Why it fails for some packages ====
+In other words, if you list 10 libraries and only 3 of them contain referenced symbols, others are silently discarded. This is a good thing but unfortunately some projects fail to list all their dependencies properly.
+This normally works because if project requires libraries //A// and //B// and //A// itself lists //B// as a dependency, both //A// and //B// get pulled in even if the project itself only lists //A//.
+Now assume that //A// is a superfluous (unneeded) dependency which gets dropped (or //A// requiring //B// is superfluous and //B// gets dropped from //A//). The symbols are no longer available.
+==== About positions ====
 Linker options are positional, and position is very important. It looks for missing symbols only in libraries coming after object file.