[ELF] Refine --export-dynamic-symbol semantics to be compatible GNU ld 2.35
GNU ld from binutils 2.35 onwards will likely support
--export-dynamic-symbol but with different semantics.
https://sourceware.org/pipermail/binutils/2020-May/111302.html
Differences:
1. -export-dynamic-symbol is not supported
2. --export-dynamic-symbol takes a glob argument
3. --export-dynamic-symbol can suppress binding the references to the definition within the shared object if (-Bsymbolic or -Bsymbolic-functions)
4. --export-dynamic-symbol does not imply -u
I don't think the first three points can affect any user.
For the fourth point, Not implying -u can lead to some archive members unfetched.
Add -u foo to restore the previous behavior.
Exact semantics:
* -no-pie or -pie: matched non-local defined symbols will be added to the dynamic symbol table.
* -shared: matched non-local STV_DEFAULT symbols will not be bound to definitions within the shared object
even if they would otherwise be due to -Bsymbolic, -Bsymbolic-functions, or --dynamic-list.
Reviewed By: psmith
Differential Revision: https://reviews.llvm.org/D80487
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index ff1e600..8f2f554 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -365,13 +365,11 @@
if (!config->shared)
return false;
- // If the dynamic list is present, it specifies preemptable symbols in a DSO.
- if (config->hasDynamicList)
+ // If -Bsymbolic or --dynamic-list is specified, or -Bsymbolic-functions is
+ // specified and the symbol is STT_FUNC, the symbol is preemptible iff it is
+ // in the dynamic list.
+ if (config->symbolic || (config->bsymbolicFunctions && sym.isFunc()))
return sym.inDynamicList;
-
- // -Bsymbolic means that definitions are not preempted.
- if (config->bsymbolic || (config->bsymbolicFunctions && sym.isFunc()))
- return false;
return true;
}
