test/link: linker tests for all export cases

Adds a linker test case for each possible export case. This means
one where no exports are done (i.e. no flags set), when the -dynamic
flag is set, and finally when --export=<value> flag(s) are set.

test/link.zig

@@ -42,6 +42,11 @@ fn addWasmCases(cases: *tests.StandaloneContext) void {
         .requires_stage2 = true,
     });
 
+    cases.addBuildFile("test/link/wasm/export/build.zig", .{
+        .build_modes = true,
+        .requires_stage2 = true,
+    });
+
     cases.addBuildFile("test/link/wasm/extern/build.zig", .{
         .build_modes = true,
         .requires_stage2 = true,

test/link/wasm/bss/build.zig

@@ -26,8 +26,7 @@ pub fn build(b: *Builder) void {
     check_lib.checkNext("name memory"); // as per linker specification
 
     // since we are importing memory, ensure it's not exported
-    check_lib.checkStart("Section export");
-    check_lib.checkNext("entries 1"); // we're exporting function 'foo' so only 1 entry
+    check_lib.checkNotPresent("Section export");
 
     // validate the name of the stack pointer
     check_lib.checkStart("Section custom");

test/link/wasm/export/build.zig

@@ -0,0 +1,48 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    const mode = b.standardReleaseOptions();
+
+    const no_export = b.addSharedLibrary("no-export", "main.zig", .unversioned);
+    no_export.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    no_export.setBuildMode(mode);
+    no_export.use_llvm = false;
+    no_export.use_lld = false;
+
+    const dynamic_export = b.addSharedLibrary("dynamic", "main.zig", .unversioned);
+    dynamic_export.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    dynamic_export.setBuildMode(mode);
+    dynamic_export.rdynamic = true;
+    dynamic_export.use_llvm = false;
+    dynamic_export.use_lld = false;
+
+    const force_export = b.addSharedLibrary("force", "main.zig", .unversioned);
+    force_export.setTarget(.{ .cpu_arch = .wasm32, .os_tag = .freestanding });
+    force_export.setBuildMode(mode);
+    force_export.export_symbol_names = &.{"foo"};
+    force_export.use_llvm = false;
+    force_export.use_lld = false;
+
+    const check_no_export = no_export.checkObject(.wasm);
+    check_no_export.checkStart("Section export");
+    check_no_export.checkNext("entries 1");
+    check_no_export.checkNext("name memory");
+    check_no_export.checkNext("kind memory");
+
+    const check_dynamic_export = dynamic_export.checkObject(.wasm);
+    check_dynamic_export.checkStart("Section export");
+    check_dynamic_export.checkNext("entries 2");
+    check_dynamic_export.checkNext("name foo");
+    check_dynamic_export.checkNext("kind function");
+
+    const check_force_export = force_export.checkObject(.wasm);
+    check_force_export.checkStart("Section export");
+    check_force_export.checkNext("entries 2");
+    check_force_export.checkNext("name foo");
+    check_force_export.checkNext("kind function");
+
+    const test_step = b.step("test", "Run linker test");
+    test_step.dependOn(&check_no_export.step);
+    test_step.dependOn(&check_dynamic_export.step);
+    test_step.dependOn(&check_force_export.step);
+}

test/link/wasm/export/main.zig

@@ -0,0 +1 @@
+export fn foo() void {}