wasm linker: don't call init functions unless object included

3 files changed, 14 insertions, 5 deletions

diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index 277d092cba..5dd51c2f12 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -117,7 +117,7 @@ object_memories: std.ArrayListUnmanaged(ObjectMemory) = .empty,
 object_relocations: std.MultiArrayList(ObjectRelocation) = .empty,
 
 /// List of initialization functions. These must be called in order of priority
-/// by the (synthetic) __wasm_call_ctors function.
+/// by the (synthetic) `__wasm_call_ctors` function.
 object_init_funcs: std.ArrayListUnmanaged(InitFunc) = .empty,
 
 /// The data section of an object has many segments. Each segment corresponds
@@ -3308,7 +3308,10 @@ pub fn prelink(wasm: *Wasm, prog_node: std.Progress.Node) link.File.FlushError!v
     }
     // Also treat init functions as roots.
     for (wasm.object_init_funcs.items) |init_func| {
-        try markFunction(wasm, init_func.function_index);
+        const func = init_func.function_index.ptr(wasm);
+        if (func.object_index.ptr(wasm).is_included) {
+            try markFunction(wasm, init_func.function_index);
+        }
     }
     wasm.functions_end_prelink = @intCast(wasm.functions.entries.len);
     wasm.function_exports_len = @intCast(wasm.function_exports.items.len);
@@ -3383,6 +3386,7 @@ fn markFunction(wasm: *Wasm, i: ObjectFunctionIndex) link.File.FlushError!void {
     const rdynamic = comp.config.rdynamic;
     const is_obj = comp.config.output_mode == .Obj;
     const function = i.ptr(wasm);
+    markObject(wasm, function.object_index);
 
     if (!is_obj and function.flags.isExported(rdynamic)) try wasm.function_exports.append(gpa, .{
         .name = function.name.unwrap().?,
@@ -3392,6 +3396,10 @@ fn markFunction(wasm: *Wasm, i: ObjectFunctionIndex) link.File.FlushError!void {
     try wasm.markRelocations(function.relocations(wasm));
 }
 
+fn markObject(wasm: *Wasm, i: ObjectIndex) void {
+    i.ptr(wasm).is_included = true;
+}
+
 /// Recursively mark alive everything referenced by the global.
 fn markGlobalImport(
     wasm: *Wasm,
diff --git a/src/link/Wasm/Flush.zig b/src/link/Wasm/Flush.zig
index d53a508f9b..390f024642 100644
--- a/src/link/Wasm/Flush.zig
+++ b/src/link/Wasm/Flush.zig
@@ -188,8 +188,6 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
     for (wasm.object_indirect_function_set.keys()) |object_function_index|
         f.indirect_function_table.putAssumeCapacity(.fromObjectFunction(wasm, object_function_index), {});
 
-    // TODO only include init functions for objects with must_link=true or
-    // which have any alive functions inside them.
     if (wasm.object_init_funcs.items.len > 0) {
         // Zig has no constructors so these are only for object file inputs.
         mem.sortUnstable(Wasm.InitFunc, wasm.object_init_funcs.items, {}, Wasm.InitFunc.lessThan);
@@ -692,7 +690,7 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
     }
 
     // When the shared-memory option is enabled, we *must* emit the 'data count' section.
-    if (f.data_segment_groups.items.len > 0 and shared_memory) {
+    {
         const header_offset = try reserveVecSectionHeader(gpa, binary_bytes);
         replaceVecSectionHeader(binary_bytes, header_offset, .data_count, @intCast(f.data_segment_groups.items.len));
     }
@@ -1644,6 +1642,7 @@ fn emitCallCtorsFunction(wasm: *const Wasm, binary_bytes: *std.ArrayListUnmanage
 
     for (wasm.object_init_funcs.items) |init_func| {
         const func = init_func.function_index.ptr(wasm);
+        if (!func.object_index.ptr(wasm).is_included) continue;
         const ty = func.type_index.ptr(wasm);
         const n_returns = ty.returns.slice(wasm).len;
 
diff --git a/src/link/Wasm/Object.zig b/src/link/Wasm/Object.zig
index 91354c3d03..ecd2630d32 100644
--- a/src/link/Wasm/Object.zig
+++ b/src/link/Wasm/Object.zig
@@ -48,6 +48,7 @@ code_section_index: ?Wasm.ObjectSectionIndex,
 global_section_index: ?Wasm.ObjectSectionIndex,
 /// Guaranteed to be non-null when data segments has nonzero length.
 data_section_index: ?Wasm.ObjectSectionIndex,
+is_included: bool,
 
 pub const RelativeSlice = struct {
     off: u32,
@@ -1414,6 +1415,7 @@ pub fn parse(
         .code_section_index = code_section_index,
         .global_section_index = global_section_index,
         .data_section_index = data_section_index,
+        .is_included = must_link,
     };
 }