[ifs] Add --strip-size flag

st_size may not be of importance to the abi if you are not using
copy relocations. This is helpful when you want to check the abi
of a shared object both when instrumented and not because asan
will increase the size of objects to include the redzone.

Differential revision: https://reviews.llvm.org/D124792

2 files changed, 8 insertions, 6 deletions

diff --git a/llvm/lib/InterfaceStub/ELFObjHandler.cpp b/llvm/lib/InterfaceStub/ELFObjHandler.cpp
index 7420e15..6f37cf6 100644
--- a/llvm/lib/InterfaceStub/ELFObjHandler.cpp
+++ b/llvm/lib/InterfaceStub/ELFObjHandler.cpp
@@ -217,7 +217,8 @@ public:
       // time as long as it is not SHN_UNDEF. Set shndx to 1, which
       // points to ".dynsym".
       uint16_t Shndx = Sym.Undefined ? SHN_UNDEF : 1;
-      DynSym.Content.add(DynStr.Content.getOffset(Sym.Name), Sym.Size, Bind,
+      uint64_t Size = Sym.Size ? *Sym.Size : 0;
+      DynSym.Content.add(DynStr.Content.getOffset(Sym.Name), Size, Bind,
                          convertIFSSymbolTypeToELF(Sym.Type), 0, Shndx);
     }
     DynSym.Size = DynSym.Content.getSize();
diff --git a/llvm/lib/InterfaceStub/IFSHandler.cpp b/llvm/lib/InterfaceStub/IFSHandler.cpp
index 92c8830..4a784c7 100644
--- a/llvm/lib/InterfaceStub/IFSHandler.cpp
+++ b/llvm/lib/InterfaceStub/IFSHandler.cpp
@@ -118,11 +118,12 @@ template <> struct MappingTraits<IFSSymbol> {
     IO.mapRequired("Type", Symbol.Type);
     // The need for symbol size depends on the symbol type.
     if (Symbol.Type == IFSSymbolType::NoType) {
-      IO.mapOptional("Size", Symbol.Size, (uint64_t)0);
-    } else if (Symbol.Type == IFSSymbolType::Func) {
-      Symbol.Size = 0;
-    } else {
-      IO.mapRequired("Size", Symbol.Size);
+      // Size is None, so we are reading it in, or it is non 0 so we
+      // should emit it.
+      if (!Symbol.Size || *Symbol.Size)
+        IO.mapOptional("Size", Symbol.Size);
+    } else if (Symbol.Type != IFSSymbolType::Func) {
+      IO.mapOptional("Size", Symbol.Size);
     }
     IO.mapOptional("Undefined", Symbol.Undefined, false);
     IO.mapOptional("Weak", Symbol.Weak, false);