[ELF] Define __start_XXX/__stop_XXX symbols where XXX is a section name

This is GNU ELF linker extension used particularly by LibC code.
If input object files contain section named XXX, and the XXX is a valid C
identifier, and there are undefined or weak symbols __start_XXX/__stop_XXX,
linker should define __start_XXX/__stop_XXX symbols point to the begin/end
of the XXX section correspondingly.

For example, without support of this extension statically linked executables
for X86_64 and Mips (maybe other) targets do not flush IO buffers at the end
of executing.

llvm-svn: 241341

1 files changed, 2 insertions, 1 deletions

diff --git a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
index c7909f5f75d..bb390101063 100644
--- a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
+++ b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
@@ -113,7 +113,7 @@ protected:
 
   /// \brief Process undefined symbols that left after resolution step.
   virtual void processUndefinedSymbol(StringRef symName,
-                                      RuntimeFile<ELFT> &file) const {}
+                                      RuntimeFile<ELFT> &file) const;
 
   /// \brief Assign addresses to atoms marking section's start and end.
   void updateScopeAtomValues(StringRef sym, StringRef sec);
@@ -144,6 +144,7 @@ protected:
 
 private:
   static StringRef maybeGetSOName(Node *node);
+  void updateScopeAtomValues(StringRef start, StringRef end, StringRef sec);
 };
 
 } // namespace elf