Handle aliases without size (e.g. weak symbol), add redefinition warnings (#630)

3 files changed, 18 insertions, 18 deletions

diff --git a/src/s2wasm.h b/src/s2wasm.h
index 8f429f96c..8595bdb44 100644
--- a/src/s2wasm.h
+++ b/src/s2wasm.h
@@ -391,7 +391,8 @@ class S2WasmBuilder {
         } else if (match("=")) {
           Name alias = getAtSeparated();
           mustMatch("@FUNCTION");
-          info->aliasedSymbols.insert({name, LinkerObject::SymbolAlias(alias, LinkerObject::Relocation::kFunction, 0)});
+          auto ret = info->aliasedSymbols.insert({name, LinkerObject::SymbolAlias(alias, LinkerObject::Relocation::kFunction, 0)});
+          if (!ret.second) std::cerr << "Unsupported data alias redefinition: " << name << ", skipping...\n";
         } else {
           abort_on("unknown directive");
         }
@@ -412,15 +413,6 @@ class S2WasmBuilder {
           s++;
           offset = getInt();
         }
-        skipWhitespace();
-
-        // get the data size
-        mustMatch(".size");
-        mustMatch(lhs.str);
-        mustMatch(",");
-        wasm::Address size = atoi(getStr().str);
-        WASM_UNUSED(size);
-        skipWhitespace();
 
         // check if the rhs is already an alias
         const auto alias = symbolInfo->aliasedSymbols.find(rhs);
@@ -430,8 +422,9 @@ class S2WasmBuilder {
         }
 
         // add the new alias
-        symbolInfo->aliasedSymbols.insert({lhs, LinkerObject::SymbolAlias(rhs,
+        auto ret = symbolInfo->aliasedSymbols.insert({lhs, LinkerObject::SymbolAlias(rhs,
           LinkerObject::Relocation::kData, offset)});
+        if (!ret.second) std::cerr << "Unsupported function alias redefinition: " << lhs << ", skipping...\n";
       }
     }
   }
@@ -470,7 +463,9 @@ class S2WasmBuilder {
     WASM_UNUSED(rhs);
     skipWhitespace();
 
-    mustMatch(".size");
+    // if no size attribute (e.g. weak symbol), skip
+    if (!match(".size")) return;
+
     mustMatch(lhs.str);
     mustMatch(",");
     Name size = getStr();
diff --git a/src/wasm-linker.cpp b/src/wasm-linker.cpp
index a2e88cfb3..628e24ecc 100644
--- a/src/wasm-linker.cpp
+++ b/src/wasm-linker.cpp
@@ -123,6 +123,7 @@ void Linker::layout() {
     }
   };
   for (auto& relocation : out.relocations) {
+    // TODO: Handle weak symbols properly, instead of always taking the weak definition.
     auto *alias = out.getAlias(relocation->symbol, relocation->kind);
     Name name = relocation->symbol;
 
diff --git a/test/dot_s/alias.s b/test/dot_s/alias.s
index 449e33f0e..121f3fc53 100644
--- a/test/dot_s/alias.s
+++ b/test/dot_s/alias.s
@@ -5,9 +5,9 @@
 	.globl	__exit
 	.type	__exit,@function
 __exit:                           # @__exit
-	i32.const	$push0=, _A
+	i32.const	$push0=, _B
 	i32.load	$push1=, 0($pop0)
-	i32.const	$push2=, ._B
+	i32.const	$push2=, ._C
 	i32.load	$push3=, 0($pop2)
 	i32.add 	$push4=, $pop1, $pop3
 # BB#0:                                 # %entry
@@ -42,7 +42,11 @@ __exit_needed = __exit@FUNCTION
 	.int32	2345
 	.size	.L__unnamed_1, 12
 
-_A = .L__unnamed_1
-	.size	_A, 12
-._B = _A+8
-	.size	._B, 4
+	.weak	.A
+._A = .L__unname_1
+	.weak	._B
+_B = .L__unnamed_1
+	.size	_B, 12
+	.weak	._C
+._C = _B+8
+	.size	._C, 4