compiler: push entry symbol name resolution into the linker

This is necessary because on COFF, the entry symbol name is not known
until the linker has looked at the set of global symbol names to
determine which of the four possible main entry points is present.

1 files changed, 33 insertions, 18 deletions

diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index b4b0f16d4a..91653ce641 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -37,6 +37,7 @@ pub const Relocation = types.Relocation;
 pub const base_tag: link.File.Tag = .wasm;
 
 base: link.File,
+entry_name: ?[]const u8,
 import_symbols: bool,
 export_symbol_names: []const []const u8,
 global_base: ?u64,
@@ -397,6 +398,7 @@ pub fn createEmpty(
     const use_llvm = comp.config.use_llvm;
     const output_mode = comp.config.output_mode;
     const shared_memory = comp.config.shared_memory;
+    const wasi_exec_model = comp.config.wasi_exec_model;
 
     // If using LLD to link, this code should produce an object file so that it
     // can be passed to LLD.
@@ -434,6 +436,13 @@ pub fn createEmpty(
         .initial_memory = options.initial_memory,
         .max_memory = options.max_memory,
         .wasi_emulated_libs = options.wasi_emulated_libs,
+
+        .entry_name = switch (options.entry) {
+            .disabled => null,
+            .default => if (output_mode != .Exe) null else defaultEntrySymbolName(wasi_exec_model),
+            .enabled => defaultEntrySymbolName(wasi_exec_model),
+            .named => |name| name,
+        },
     };
     if (use_llvm and comp.config.have_zcu) {
         wasm.llvm_object = try LlvmObject.create(arena, comp);
@@ -3042,7 +3051,7 @@ fn setupExports(wasm: *Wasm) !void {
 fn setupStart(wasm: *Wasm) !void {
     const comp = wasm.base.comp;
     // do not export entry point if user set none or no default was set.
-    const entry_name = comp.config.entry orelse return;
+    const entry_name = wasm.entry_name orelse return;
 
     const symbol_loc = wasm.findGlobalSymbol(entry_name) orelse {
         log.err("Entry symbol '{s}' missing, use '-fno-entry' to suppress", .{entry_name});
@@ -3475,8 +3484,8 @@ fn resetState(wasm: *Wasm) void {
 }
 
 pub fn flush(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) link.File.FlushError!void {
-    const use_lld = build_options.have_llvm and wasm.base.comp.config.use_lld;
-    const use_llvm = wasm.base.comp.config.use_llvm;
+    const use_lld = build_options.have_llvm and comp.config.use_lld;
+    const use_llvm = comp.config.use_llvm;
 
     if (use_lld) {
         return wasm.linkWithLLD(comp, prog_node);
@@ -3492,7 +3501,7 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
     const tracy = trace(@src());
     defer tracy.end();
 
-    const gpa = wasm.base.comp.gpa;
+    const gpa = comp.gpa;
     const shared_memory = comp.config.shared_memory;
     const import_memory = comp.config.import_memory;
 
@@ -3503,8 +3512,8 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
 
     const directory = wasm.base.emit.directory; // Just an alias to make it shorter to type.
     const full_out_path = try directory.join(arena, &[_][]const u8{wasm.base.emit.sub_path});
-    const opt_zcu = wasm.base.comp.module;
-    const use_llvm = wasm.base.comp.config.use_llvm;
+    const opt_zcu = comp.module;
+    const use_llvm = comp.config.use_llvm;
 
     // If there is no Zig code to compile, then we should skip flushing the output file because it
     // will not be part of the linker line anyway.
@@ -3535,7 +3544,7 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
     defer if (!wasm.base.disable_lld_caching) man.deinit();
     var digest: [Cache.hex_digest_len]u8 = undefined;
 
-    const objects = wasm.base.comp.objects;
+    const objects = comp.objects;
 
     // NOTE: The following section must be maintained to be equal
     // as the section defined in `linkWithLLD`
@@ -3556,7 +3565,7 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
         }
         try man.addOptionalFile(module_obj_path);
         try man.addOptionalFile(compiler_rt_path);
-        man.hash.addOptionalBytes(wasm.base.comp.config.entry);
+        man.hash.addOptionalBytes(wasm.entry_name);
         man.hash.add(wasm.base.stack_size);
         man.hash.add(wasm.base.build_id);
         man.hash.add(import_memory);
@@ -3605,12 +3614,12 @@ fn linkWithZld(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) l
     var positionals = std.ArrayList([]const u8).init(arena);
     try positionals.ensureUnusedCapacity(objects.len);
 
-    const target = wasm.base.comp.root_mod.resolved_target.result;
-    const output_mode = wasm.base.comp.config.output_mode;
-    const link_mode = wasm.base.comp.config.link_mode;
-    const link_libc = wasm.base.comp.config.link_libc;
-    const link_libcpp = wasm.base.comp.config.link_libcpp;
-    const wasi_exec_model = wasm.base.comp.config.wasi_exec_model;
+    const target = comp.root_mod.resolved_target.result;
+    const output_mode = comp.config.output_mode;
+    const link_mode = comp.config.link_mode;
+    const link_libc = comp.config.link_libc;
+    const link_libcpp = comp.config.link_libcpp;
+    const wasi_exec_model = comp.config.wasi_exec_model;
 
     // When the target os is WASI, we allow linking with WASI-LIBC
     if (target.os.tag == .wasi) {
@@ -4648,7 +4657,7 @@ fn linkWithLLD(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !
         }
         try man.addOptionalFile(module_obj_path);
         try man.addOptionalFile(compiler_rt_path);
-        man.hash.addOptionalBytes(wasm.base.comp.config.entry);
+        man.hash.addOptionalBytes(wasm.entry_name);
         man.hash.add(wasm.base.stack_size);
         man.hash.add(wasm.base.build_id);
         man.hash.add(import_memory);
@@ -4799,9 +4808,8 @@ fn linkWithLLD(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !
             try argv.append("--export-dynamic");
         }
 
-        if (comp.config.entry) |entry| {
-            try argv.append("--entry");
-            try argv.append(entry);
+        if (wasm.entry_name) |entry_name| {
+            try argv.appendSlice(&.{ "--entry", entry_name });
         } else {
             try argv.append("--no-entry");
         }
@@ -5347,3 +5355,10 @@ fn mark(wasm: *Wasm, loc: SymbolLoc) !void {
         try wasm.mark(target_loc.finalLoc(wasm));
     }
 }
+
+fn defaultEntrySymbolName(wasi_exec_model: std.builtin.WasiExecModel) []const u8 {
+    return switch (wasi_exec_model) {
+        .reactor => "_initialize",
+        .command => "_start",
+    };
+}