test/link: add test case for function table

Adds 3 linker tests to verify the indirect function table
functionality for importing, exporting and its regular definitions.

Author: Luukdegram

test/link.zig

@@ -58,6 +58,11 @@ fn addWasmCases(cases: *tests.StandaloneContext) void {
         .requires_stage2 = true,
     });
 
+    cases.addBuildFile("test/link/wasm/function-table/build.zig", .{
+        .build_modes = true,
+        .requires_stage2 = true,
+    });
+
     cases.addBuildFile("test/link/wasm/infer-features/build.zig", .{
         .requires_stage2 = true,
     });

test/link/wasm/function-table/build.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+const Builder = std.build.Builder;
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+
+    const test_step = b.step("test", "Test");
+    test_step.dependOn(b.getInstallStep());
+
+    const import_table = b.addSharedLibrary("lib", "lib.zig", .unversioned);
+    import_table.setBuildMode(mode);
+    import_table.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    import_table.use_llvm = false;
+    import_table.use_lld = false;
+    import_table.import_table = true;
+
+    const export_table = b.addSharedLibrary("lib", "lib.zig", .unversioned);
+    export_table.setBuildMode(mode);
+    export_table.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    export_table.use_llvm = false;
+    export_table.use_lld = false;
+    export_table.export_table = true;
+
+    const regular_table = b.addSharedLibrary("lib", "lib.zig", .unversioned);
+    regular_table.setBuildMode(mode);
+    regular_table.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    regular_table.use_llvm = false;
+    regular_table.use_lld = false;
+
+    const check_import = import_table.checkObject(.wasm);
+    const check_export = export_table.checkObject(.wasm);
+    const check_regular = regular_table.checkObject(.wasm);
+
+    check_import.checkStart("Section import");
+    check_import.checkNext("entries 1");
+    check_import.checkNext("module env");
+    check_import.checkNext("name __indirect_function_table");
+    check_import.checkNext("kind table");
+    check_import.checkNext("type funcref");
+    check_import.checkNext("min 1"); // 1 function pointer
+    check_import.checkNotPresent("max"); // when importing, we do not provide a max
+    check_import.checkNotPresent("Section table"); // we're importing it
+
+    check_export.checkStart("Section export");
+    check_export.checkNext("entries 2");
+    check_export.checkNext("name __indirect_function_table"); // as per linker specification
+    check_export.checkNext("kind table");
+
+    check_regular.checkStart("Section table");
+    check_regular.checkNext("entries 1");
+    check_regular.checkNext("type funcref");
+    check_regular.checkNext("min 2"); // index starts at 1 & 1 function pointer = 2.
+    check_regular.checkNext("max 2");
+    check_regular.checkStart("Section element");
+    check_regular.checkNext("entries 1");
+    check_regular.checkNext("table index 0");
+    check_regular.checkNext("i32.const 1"); // we want to start function indexes at 1
+    check_regular.checkNext("indexes 1"); // 1 function pointer
+
+    test_step.dependOn(&check_import.step);
+    test_step.dependOn(&check_export.step);
+    test_step.dependOn(&check_regular.step);
+}

test/link/wasm/function-table/lib.zig

@@ -0,0 +1,7 @@
+var func: *const fn () void = &bar;
+
+export fn foo() void {
+    func();
+}
+
+fn bar() void {}