From 21e14cce23582fcd622b97d643a4e9b2f10a0583 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Tue, 16 Jun 2020 12:23:25 -0700
Subject: [PATCH] [lld][WebAssembly] Allow ctors functions that return values

Some projects use the constructor attribute on functions that also
return values.  In this case we just ignore them.

The error was reported in the libgpg-error project that marks
gpg_err_init with the `__constructor__` attribute.

Differential Revision: https://reviews.llvm.org/D81962
---
 lld/test/wasm/ctor_return_value.s | 46 +++++++++++++++++++++++++++++++++++++++
 lld/wasm/Writer.cpp               |  7 ++++--
 2 files changed, 51 insertions(+), 2 deletions(-)
 create mode 100644 lld/test/wasm/ctor_return_value.s

diff --git a/lld/test/wasm/ctor_return_value.s b/lld/test/wasm/ctor_return_value.s
new file mode 100644
index 0000000..8fa28ea
--- /dev/null
+++ b/lld/test/wasm/ctor_return_value.s
@@ -0,0 +1,46 @@
+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
+# RUN: wasm-ld %t.o -o %t.wasm
+# RUN: obj2yaml %t.wasm | FileCheck %s
+
+  .globl  myctor
+myctor:
+  .functype myctor () -> (i32)
+  i32.const 1
+
+  end_function
+
+  .globl  _start
+_start:
+  .functype _start () -> ()
+  call __wasm_call_ctors
+  end_function
+
+  .section  .init_array.100,"",@
+  .p2align  2
+  .int32  myctor
+  .int32  myctor
+  .int32  myctor
+
+.type __wasm_call_ctors,@function
+
+#      CHECK:   - Type:            CODE
+# CHECK-NEXT:     Functions:
+# CHECK-NEXT:       - Index:           0
+# CHECK-NEXT:         Locals:          []
+# CHECK-NEXT:         Body:            10011A10011A10011A0B
+# CHECK-NEXT:       - Index:           1
+# CHECK-NEXT:         Locals:          []
+# CHECK-NEXT:         Body:            41010B
+# CHECK-NEXT:       - Index:           2
+# CHECK-NEXT:         Locals:          []
+# CHECK-NEXT:         Body:            1080808080000B
+# CHECK-NEXT:   - Type:            CUSTOM
+# CHECK-NEXT:     Name:            name
+# CHECK-NEXT:     FunctionNames:
+# CHECK-NEXT:       - Index:           0
+# CHECK-NEXT:         Name:            __wasm_call_ctors
+# CHECK-NEXT:       - Index:           1
+# CHECK-NEXT:         Name:            myctor
+# CHECK-NEXT:       - Index:           2
+# CHECK-NEXT:         Name:            _start
+# CHECK-NEXT: ...
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index 8cfab83..0434a4c 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -913,6 +913,9 @@ void Writer::createCallCtorsFunction() {
     for (const WasmInitEntry &f : initFunctions) {
       writeU8(os, WASM_OPCODE_CALL, "CALL");
       writeUleb128(os, f.sym->getFunctionIndex(), "function index");
+      for (size_t i = 0; i < f.sym->signature->Returns.size(); i++) {
+        writeU8(os, WASM_OPCODE_DROP, "DROP");
+      }
     }
     writeU8(os, WASM_OPCODE_END, "END");
   }
@@ -977,8 +980,8 @@ void Writer::calculateInitFunctions() {
       if (sym->isDiscarded())
         continue;
       assert(sym->isLive());
-      if (*sym->signature != WasmSignature{{}, {}})
-        error("invalid signature for init func: " + toString(*sym));
+      if (sym->signature->Params.size() != 0)
+        error("constructor functions cannot take arguments: " + toString(*sym));
       LLVM_DEBUG(dbgs() << "initFunctions: " << toString(*sym) << "\n");
       initFunctions.emplace_back(WasmInitEntry{sym, f.Priority});
     }
-- 
2.7.4