can libs use symbols defined in app

jackandking · 12-01-2008, 08:14 PM

my problem keyword is "undefined symbol _xxx"

readelf find the symbol defined in the application like:
... FUNC GLOBAL DEFAULT 12 _xxx

readelf also find the symbol used in the library like:
... NOTYPE GLOBAL DEFAULT UND _xxx

ldd show the application need the library like:
ldd applicaton
library => ...

the error msg at run is:
application: symbol lookup error: library: undefined symbol: _xxx

I know it's a bad idea to let the library depend on the application, but sometime this is a convenient way the do some test.

jackandking · 12-04-2008, 08:50 AM

I made a mistake, the symbol in the app is actually in the .symtab section, not in the .dynsym section, so it's unavailabe in runtime.

Interesting thing is that once the symbol is used in the app, the symbol will be put into the .dynsym section. In this way, lib(shared object) can use the symbol defined in app successfully.

maybe some one can give the detailed explanation.
thanks in advance.