[WebAssembly] Disallow weak undefined globals in the object format

This implements https://github.com/WebAssembly/tool-conventions/pull/47

Differential Revision: https://reviews.llvm.org/D44201

llvm-svn: 327146

2 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 87ef0d927ee..a05948e2946 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -1024,6 +1024,9 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
         Imports.push_back(Import);
         WasmIndices[&WS] = NumFunctionImports++;
       } else if (WS.isGlobal()) {
+        if (WS.isWeak())
+          report_fatal_error("undefined global symbol cannot be weak");
+
         wasm::WasmImport Import;
         Import.Module = WS.getModuleName();
         Import.Field = WS.getName();
diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 3b18e194d02..65ae0639d4f 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -422,6 +422,11 @@ Error WasmObjectFile::parseLinkingSectionSymtab(const uint8_t *&Ptr,
           IsDefined != isDefinedGlobalIndex(Info.ElementIndex))
         return make_error<GenericBinaryError>("invalid global symbol index",
                                               object_error::parse_failed);
+      if (!IsDefined &&
+          (Info.Flags & wasm::WASM_SYMBOL_BINDING_MASK) ==
+              wasm::WASM_SYMBOL_BINDING_WEAK)
+        return make_error<GenericBinaryError>("undefined weak global symbol",
+                                              object_error::parse_failed);
       if (IsDefined) {
         Info.Name = readString(Ptr);
         unsigned GlobalIndex = Info.ElementIndex - NumImportedGlobals;