Handle extra info in dylink section (#4112)

If extra data is found in this section simply propagate it.

Also, remove some dead code from wasm-binary.cpp.

8 files changed, 38 insertions, 43 deletions

diff --git a/scripts/binaryen-lit.in b/scripts/binaryen-lit.in
index f26540bc3..821757082 100755
--- a/scripts/binaryen-lit.in
+++ b/scripts/binaryen-lit.in
@@ -27,7 +27,5 @@ builtin_parameters = {
     }
 }
 
-print(builtin_parameters)
-
 if __name__ == '__main__':
     main(builtin_parameters)
diff --git a/src/passes/Print.cpp b/src/passes/Print.cpp
index 3b072a469..4fa38442c 100644
--- a/src/passes/Print.cpp
+++ b/src/passes/Print.cpp
@@ -2891,6 +2891,10 @@ struct PrintSExpression : public UnifiedExpressionVisitor<PrintSExpression> {
     for (auto& neededDynlib : dylinkSection->neededDynlibs) {
       doIndent(o, indent) << ";;   needed dynlib: " << neededDynlib << '\n';
     }
+    if (dylinkSection->tail.size()) {
+      doIndent(o, indent) << ";;   extra dylink data, size "
+                          << dylinkSection->tail.size() << "\n";
+    }
   }
   void visitModule(Module* curr) {
     currModule = curr;
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 6938214d5..260bacecf 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -1242,6 +1242,7 @@ public:
   void writeInlineString(const char* name);
   void writeEscapedName(const char* name);
   void writeInlineBuffer(const char* data, size_t size);
+  void writeData(const char* data, size_t size);
 
   struct Buffer {
     const char* data;
@@ -1251,12 +1252,6 @@ public:
       : data(data), size(size), pointerLocation(pointerLocation) {}
   };
 
-  std::vector<Buffer> buffersToWrite;
-
-  void emitBuffer(const char* data, size_t size);
-  void emitString(const char* str);
-  void finishUp();
-
   Module* getModule() { return wasm; }
 
   void writeType(Type type);
diff --git a/src/wasm.h b/src/wasm.h
index 00de04623..b6e57525f 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -1825,6 +1825,7 @@ class DylinkSection {
 public:
   Index memorySize, memoryAlignment, tableSize, tableAlignment;
   std::vector<Name> neededDynlibs;
+  std::vector<char> tail;
 };
 
 class Module {
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index ae0e24759..ab229f111 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -84,8 +84,6 @@ void WasmBinaryWriter::write() {
 
   writeLateUserSections();
   writeFeaturesSection();
-
-  finishUp();
 }
 
 void WasmBinaryWriter::writeHeader() {
@@ -1087,6 +1085,9 @@ void WasmBinaryWriter::writeDylinkSection() {
   for (auto& neededDynlib : wasm->dylinkSection->neededDynlibs) {
     writeInlineString(neededDynlib.c_str());
   }
+
+  writeData(wasm->dylinkSection->tail.data(), wasm->dylinkSection->tail.size());
+
   finishSection(start);
 }
 
@@ -1131,12 +1132,16 @@ void WasmBinaryWriter::writeExtraDebugLocation(Expression* curr,
   }
 }
 
+void WasmBinaryWriter::writeData(const char* data, size_t size) {
+  for (size_t i = 0; i < size; i++) {
+    o << int8_t(data[i]);
+  }
+}
+
 void WasmBinaryWriter::writeInlineString(const char* name) {
   int32_t size = strlen(name);
   o << U32LEB(size);
-  for (int32_t i = 0; i < size; i++) {
-    o << int8_t(name[i]);
-  }
+  writeData(name, size);
 }
 
 static bool isHexDigit(char ch) {
@@ -1173,36 +1178,7 @@ void WasmBinaryWriter::writeEscapedName(const char* name) {
 
 void WasmBinaryWriter::writeInlineBuffer(const char* data, size_t size) {
   o << U32LEB(size);
-  for (size_t i = 0; i < size; i++) {
-    o << int8_t(data[i]);
-  }
-}
-
-void WasmBinaryWriter::emitBuffer(const char* data, size_t size) {
-  assert(size > 0);
-  buffersToWrite.emplace_back(data, size, o.size());
-  // placeholder, we'll fill in the pointer to the buffer later when we have it
-  o << uint32_t(0);
-}
-
-void WasmBinaryWriter::emitString(const char* str) {
-  BYN_TRACE("emitString " << str << std::endl);
-  emitBuffer(str, strlen(str) + 1);
-}
-
-void WasmBinaryWriter::finishUp() {
-  BYN_TRACE("finishUp\n");
-  // finish buffers
-  for (const auto& buffer : buffersToWrite) {
-    BYN_TRACE("writing buffer"
-              << (int)buffer.data[0] << "," << (int)buffer.data[1] << " at "
-              << o.size() << " and pointer is at " << buffer.pointerLocation
-              << "\n");
-    o.writeAt(buffer.pointerLocation, (uint32_t)o.size());
-    for (size_t i = 0; i < buffer.size; i++) {
-      o << (uint8_t)buffer.data[i];
-    }
-  }
+  writeData(data, size);
 }
 
 void WasmBinaryWriter::writeType(Type type) {
@@ -3289,6 +3265,10 @@ void WasmBinaryBuilder::readDylink(size_t payloadLen) {
     wasm.dylinkSection->neededDynlibs.push_back(getInlineString());
   }
 
+  size_t remaining = (sectionPos + payloadLen) - pos;
+  auto tail = getByteView(remaining);
+  wasm.dylinkSection->tail = {tail.first, tail.second};
+
   if (pos != sectionPos + payloadLen) {
     throwError("bad features section size");
   }
diff --git a/test/lit/binary/dylink.test b/test/lit/binary/dylink.test
new file mode 100644
index 000000000..72341c9ba
--- /dev/null
+++ b/test/lit/binary/dylink.test
@@ -0,0 +1,15 @@
+# Verify that extra bytes in the dylink section are preserved.
+#
+# `dylink.test.wasm` was generated using emscripten to build a side
+# module with two TLS exports (which adds extra information to the
+# dylink section) using:
+#  `emcc -s SIDE_MODULE side.c`
+#
+# side.c:
+#   _Thread_local int foo = 10;
+#   _Thread_local int bar = 11;
+#
+# and then removing all sections except the dylink section using:
+#  `llvm-objcopy --only-section=dylink`
+RUN: wasm-opt -O1 %s.wasm -o %t.o
+RUN: cmp %s.wasm %t.o
diff --git a/test/lit/binary/dylink.test.wasm b/test/lit/binary/dylink.test.wasm
new file mode 100755
index 000000000..401028d96
--- /dev/null
+++ b/test/lit/binary/dylink.test.wasm
diff --git a/test/lit/lit.cfg.py b/test/lit/lit.cfg.py
index 23b0c3de6..ac89a5991 100644
--- a/test/lit/lit.cfg.py
+++ b/test/lit/lit.cfg.py
@@ -10,6 +10,8 @@ config.test_exec_root = os.path.join(config.binaryen_build_root, 'test')
 
 # Replace all Binaryen tools with their absolute paths
 bin_dir = os.path.join(config.binaryen_build_root, 'bin')
+assert(os.path.isdir(bin_dir))
+
 for tool_file in os.listdir(bin_dir):
     tool_path = config.binaryen_build_root + '/bin/' + tool_file
     tool = tool_file[:-4] if tool_file.endswith('.exe') else tool_file