Skip processing UNSUPPORTED functions in the generator

SANDBOX_UNSUPPORTED("reason") is used to skip functions that are currently not
supported by the code generator. Skip processing them.

PiperOrigin-RevId: 889277347
Change-Id: I4cd19909b1d401bebd711b712528163db69b9230

Author: Sandboxed API Team

sandboxed_api/annotations_unimplemented.h

@@ -51,4 +51,8 @@
 #define SANDBOX_LIFETIME_BOUND(opaque_other) \
   [[clang::annotate("sandbox", "lifetime_bound", #opaque_other)]]
 
+// This annotation is only used for testing purposes. Please do not use it.
+#define SANDBOX_UNIMPLEMENTED_TEST \
+  [[clang::annotate("sandbox", "unimplemented_test")]]
+
 #endif  // SANDBOXED_API_ANNOTATIONS_UNIMPLEMENTED_H_

sandboxed_api/tests/testcases/lwbox_sandbox.cc

@@ -4,4 +4,5 @@
 // same file, we need a separate annotation file for SANDBOX_FUNCS.
 SANDBOX_FUNCS(mylib_is_sandboxed, mylib_scalar_types, mylib_add, mylib_copy,
               mylib_copy_raw, mylib_expected_syscall1, mylib_expected_syscall2,
-              mylib_unexpected_syscall1, mylib_unexpected_syscall2);
+              mylib_unexpected_syscall1, mylib_unexpected_syscall2,
+              mylib_func_with_todo);

sandboxed_api/tests/testcases/replaced_library.h

@@ -26,6 +26,7 @@
 
 #include "absl/strings/string_view.h"
 #include "sandboxed_api/annotations.h"
+#include "sandboxed_api/annotations_unimplemented.h"
 
 bool mylib_is_sandboxed();
 
@@ -47,4 +48,10 @@ void mylib_unexpected_syscall2();
 // SANDBOX_FUNCS/SANDBOX_IGNORE_FUNCS annotations.
 void mylib_func_with_unsupported_arg(union mylib_union* arg);
 
+// This function has a SANDBOX_UNSUPPORTED annotation and should be ignored
+// without causing errors.
+SANDBOX_UNSUPPORTED("This function is not supported for testing purposes.")
+void mylib_func_with_todo(
+    const char* arg SANDBOX_UNIMPLEMENTED_TEST SANDBOX_IN_PTR);
+
 #endif  // SANDBOXED_API_SANDBOX2_TESTCASES_REPLACED_LIBRARY_H_

sandboxed_api/tools/clang_generator/sandboxed_library_emitter.cc

@@ -776,10 +776,13 @@ absl::Status SandboxedLibraryEmitter::AddFunction(clang::FunctionDecl* decl) {
   // Also check that they are consistent with the other annotations.
   // If it is a HOST thunk, it needs to be attached to the original function.
 
+  bool has_unsupported_annotation = false;
   auto annotations_status = GetSandboxAnnotations(decl);
   if (annotations_status.ok()) {
     for (const auto& ann : *annotations_status) {
-      if (ann.name == "host_thunk") {
+      if (ann.name == "unsupported") {
+        has_unsupported_annotation = true;
+      } else if (ann.name == "host_thunk") {
         if (ann.args.empty()) {
           return absl::NotFoundError(
               "Host thunk doesn't not specify the function name.");
@@ -856,6 +859,10 @@ absl::Status SandboxedLibraryEmitter::AddFunction(clang::FunctionDecl* decl) {
     }
   }
 
+  if (has_unsupported_annotation) {
+    return absl::OkStatus();
+  }
+
   if (ignore_funcs_.contains(decl->getNameAsString()) ||
       (!sandbox_funcs_.empty() &&
        !sandbox_funcs_.contains(decl->getNameAsString()))) {