Merge pull request #17815 from Luukdegram/wasm-no-entry

wasm-linker: implement `-fno-entry` and correctly pass `--shared` and `--pie` when given

2 files changed, 27 insertions, 6 deletions

diff --git a/lib/std/Build/Step/Compile.zig b/lib/std/Build/Step/Compile.zig
index 9ede31c917..2d08541545 100644
--- a/lib/std/Build/Step/Compile.zig
+++ b/lib/std/Build/Step/Compile.zig
@@ -189,7 +189,8 @@ dll_export_fns: ?bool = null,
 
 subsystem: ?std.Target.SubSystem = null,
 
-entry_symbol_name: ?[]const u8 = null,
+/// How the linker must handle the entry point of the executable.
+entry: Entry = .default,
 
 /// List of symbols forced as undefined in the symbol table
 /// thus forcing their resolution by the linker.
@@ -304,6 +305,18 @@ const FrameworkLinkInfo = struct {
     weak: bool = false,
 };
 
+const Entry = union(enum) {
+    /// Let the compiler decide whether to make an entry point and what to name
+    /// it.
+    default,
+    /// The executable will have no entry point.
+    disabled,
+    /// The executable will have an entry point with the default symbol name.
+    enabled,
+    /// The executable will have an entry point with the specified symbol name.
+    symbol_name: []const u8,
+};
+
 pub const IncludeDir = union(enum) {
     path: LazyPath,
     path_system: LazyPath,
@@ -1418,9 +1431,13 @@ fn make(step: *Step, prog_node: *std.Progress.Node) !void {
         try zig_args.append(try std.fmt.allocPrint(b.allocator, "-ofmt={s}", .{@tagName(ofmt)}));
     }
 
-    if (self.entry_symbol_name) |entry| {
-        try zig_args.append("--entry");
-        try zig_args.append(entry);
+    switch (self.entry) {
+        .default => {},
+        .disabled => try zig_args.append("-fno-entry"),
+        .enabled => try zig_args.append("-fentry"),
+        .symbol_name => |entry_name| {
+            try zig_args.append(try std.fmt.allocPrint(b.allocator, "-fentry={s}", .{entry_name}));
+        },
     }
 
     {
diff --git a/lib/std/start.zig b/lib/std/start.zig
index 7925ea9168..ff21ed8187 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -82,11 +82,15 @@ comptime {
                     .reactor => "_initialize",
                     .command => "_start",
                 };
-                if (!@hasDecl(root, wasm_start_sym)) {
+                if (!@hasDecl(root, wasm_start_sym) and @hasDecl(root, "main")) {
+                    // Only call main when defined. For WebAssembly it's allowed to pass `-fno-entry` in which
+                    // case it's not required to provide an entrypoint such as main.
                     @export(wasi_start, .{ .name = wasm_start_sym });
                 }
             } else if (native_arch.isWasm() and native_os == .freestanding) {
-                if (!@hasDecl(root, start_sym_name)) @export(wasm_freestanding_start, .{ .name = start_sym_name });
+                // Only call main when defined. For WebAssembly it's allowed to pass `-fno-entry` in which
+                // case it's not required to provide an entrypoint such as main.
+                if (!@hasDecl(root, start_sym_name) and @hasDecl(root, "main")) @export(wasm_freestanding_start, .{ .name = start_sym_name });
             } else if (native_os != .other and native_os != .freestanding) {
                 if (!@hasDecl(root, start_sym_name)) @export(_start, .{ .name = start_sym_name });
             }