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Solving symbols from different shared objects?
- From: Han Shen <shenhan at google dot com>
- To: Cary Coutant <ccoutant at gmail dot com>, binutils <binutils at sourceware dot org>
- Cc: Eric Christopher <echristo at google dot com>, Jing Yu <jingyu at google dot com>, Jeff Bailey <jeffbailey at google dot com>, Brooks Moses <bmoses at google dot com>
- Date: Tue, 20 Sep 2016 18:28:45 -0700
- Subject: Solving symbols from different shared objects?
- Authentication-results: sourceware.org; auth=none
Hi Cary, we are testing trunk binutils and found lots of failures, one
scenario (unresolved reference to "dlsym") is linking an executable
that involves 3 shared libraries, A.so, B.so and libdl.so.
In A.so, there is an undefined, un-versioned "dlsym"
In B.so, there is an undefined, versioned "dlsym@@GLIBC_2.2.5"
In libdl.so, there is the definition for "dlsym@@GLIBC_2.2.5".
The old binutils (forked at the end of 2014), which we are now using,
solves dlsym in A.so using definition in libdl.so in
However, in fixing the bug -
Symbol_table::define_default_version is modified, so that definition
in libdl.so no longer applies to A.so, the rationale being (quote from
comment) "if two symbols are from different objects, they are
To fix the problem, I modified it so that "if two symbols are from
different objects, *and both of them are defined*, they are different
symbols.", as the patch illustrates below -
diff --git a/gold/symtab.cc b/gold/symtab.cc
index b31794a..cdeef7f 100644
@@ -881,7 +881,7 @@
else if (pdef->second->is_from_dynobj()
- && sym->is_from_dynobj()
+ && sym->is_from_dynobj() && pdef->second->is_defined()
&& pdef->second->object() != sym->object())
Do you think this is a a reasonable fix?