[ELF] A shared object is needed if any of its occurrences is needed
Summary:
If a DSO appears more than once with and without --as-needed, ld.bfd and gold consider --no-as-needed to takes precedence over --as-needed. lld didn't and this patch makes it do so.
This makes it a bit away from the position-dependent behavior (how
different occurrences of the same DSO interact) and protects us from
some mysterious runtime errors: if some interceptor libraries add their
own --no-as-needed dependencies (e.g. librt.so), and the user
application specifies -Wl,--as-needed -lrt , the absence of the
DT_NEEDED entry would make dlsym(RTLD_NEXT, "clock_gettime") return NULL
and would break at runtime.
Reviewers: ruiu, espindola
Reviewed By: ruiu
Subscribers: emaste, arichardson, llvm-commits
Differential Revision: https://reviews.llvm.org/D56089
llvm-svn: 350105
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index ba74637..7615e12 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -94,8 +94,20 @@
if (auto *F = dyn_cast<SharedFile<ELFT>>(File)) {
// DSOs are uniquified not by filename but by soname.
F->parseSoName();
- if (errorCount() || !SoNames.insert(F->SoName).second)
+ if (errorCount())
return;
+
+ // If a DSO appears more than once on the command line with and without
+ // --as-needed, --no-as-needed takes precedence over --as-needed because a
+ // user can add an extra DSO with --no-as-needed to force it to be added to
+ // the dependency list.
+ DenseMap<StringRef, InputFile *>::iterator It;
+ bool WasInserted;
+ std::tie(It, WasInserted) = SoNames.try_emplace(F->SoName, F);
+ cast<SharedFile<ELFT>>(It->second)->IsNeeded |= F->IsNeeded;
+ if (!WasInserted)
+ return;
+
SharedFiles.push_back(F);
F->parseRest();
return;