pw_trace: Fix backends that don't support all trace macros

Bug: b/256681191
Change-Id: Idaee79768fba4d0d95da6ce9e114e3135987cc7a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/116791
Pigweed-Auto-Submit: Erik Gilling <konkers@google.com>
Reviewed-by: Ted Pudlik <tpudlik@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Rob Oliver <rgoliver@google.com>

4 files changed, 90 insertions, 4 deletions

diff --git a/pw_trace/BUILD.bazel b/pw_trace/BUILD.bazel
index 38b2188cf..4ecf9f64e 100644
--- a/pw_trace/BUILD.bazel
+++ b/pw_trace/BUILD.bazel
@@ -107,6 +107,25 @@ pw_cc_test(
     ],
 )
 
+pw_cc_test(
+    name = "trace_zero_facade_test",
+    srcs = [
+        "pw_trace_zero/public_overrides/pw_trace_backend/trace_backend.h",
+        "trace_backend_compile_test.cc",
+        "trace_backend_compile_test_c.c",
+    ],
+    includes = [
+        "pw_trace_zero",
+        "pw_trace_zero/public_overrides",
+    ],
+    deps = [
+        ":facade",
+        ":pw_trace",
+        "//pw_preprocessor",
+        "//pw_unit_test",
+    ],
+)
+
 pw_cc_library(
     name = "trace_null_test",
     srcs = [
@@ -127,7 +146,10 @@ pw_cc_library(
     srcs = ["example/sample_app.cc"],
     hdrs = ["example/public/pw_trace/example/sample_app.h"],
     includes = ["example/public"],
-    deps = ["//pw_trace"],
+    deps = [
+        "//pw_ring_buffer",
+        "//pw_trace",
+    ],
 )
 
 pw_cc_binary(
diff --git a/pw_trace/BUILD.gn b/pw_trace/BUILD.gn
index a62d1af46..64e7a78b7 100644
--- a/pw_trace/BUILD.gn
+++ b/pw_trace/BUILD.gn
@@ -16,6 +16,7 @@ import("//build_overrides/pigweed.gni")
 
 import("$dir_pw_build/facade.gni")
 import("$dir_pw_docgen/docs.gni")
+import("$dir_pw_unit_test/facade_test.gni")
 import("$dir_pw_unit_test/test.gni")
 import("backend.gni")
 
@@ -53,6 +54,7 @@ pw_test_group("tests") {
   tests = [
     ":trace_facade_test",
     ":trace_null_test",
+    ":trace_zero_backend_test",
   ]
   if (pw_trace_BACKEND != "") {
     tests += [ ":trace_backend_compile_test" ]
@@ -88,6 +90,32 @@ pw_test("trace_backend_compile_test") {
   ]
 }
 
+config("zero_config") {
+  include_dirs = [ "pw_trace_zero/public_overrides" ]
+  visibility = [ ":*" ]
+}
+
+pw_source_set("zero") {
+  public_configs = [
+    ":default_config",
+    ":zero_config",
+  ]
+  public = [ "pw_trace_zero/public_overrides/pw_trace_backend/trace_backend.h" ]
+}
+
+pw_facade_test("trace_zero_backend_test") {
+  build_args = {
+    pw_trace_BACKEND = ":zero"
+  }
+
+  deps = [ ":pw_trace" ]
+
+  sources = [
+    "trace_backend_compile_test.cc",
+    "trace_backend_compile_test_c.c",
+  ]
+}
+
 pw_test("trace_null_test") {
   sources = [
     "trace_null_test.cc",
diff --git a/pw_trace/public/pw_trace/internal/trace_internal.h b/pw_trace/public/pw_trace/internal/trace_internal.h
index 9355b49ca..f6262eec4 100644
--- a/pw_trace/public/pw_trace/internal/trace_internal.h
+++ b/pw_trace/public/pw_trace/internal/trace_internal.h
@@ -49,9 +49,12 @@
 
 // Default: behaviour for unimplemented trace event types
 #ifndef _PW_TRACE_DISABLED
-#define _PW_TRACE_DISABLED(...) \
-  do {                          \
-  } while (0)
+static inline void _pw_trace_disabled(int x, ...) { (void)x; }
+// `_PW_TRACE_DISABLED` must be called with at least one arg.
+#define _PW_TRACE_DISABLED(...)           \
+  do {                                    \
+    _pw_trace_disabled(0, ##__VA_ARGS__); \
+  } while (false)
 #endif  // _PW_TRACE_DISABLED
 
 // Default: label used for PW_TRACE_FUNCTION trace events
@@ -270,6 +273,11 @@
   _PW_TRACE_SCOPE_ARGS2(PW_TRACE_FLAGS, PW_TRACE_FUNCTION_LABEL)
 #define _PW_TRACE_FUNCTION_FLAGS_ARGS1(flag) \
   _PW_TRACE_SCOPE_ARGS2(flag, PW_TRACE_FUNCTION_LABEL)
+#else  // PW_TRACE_TYPE_DURATION_GROUP_END
+#define _PW_TRACE_SCOPE_ARGS2(...) _PW_TRACE_DISABLED(__VA_ARGS__)
+#define _PW_TRACE_FUNCTION_ARGS0()  // No need to/can't call _PW_TRACE_DISABLED
+                                    // with zero args.
+#define _PW_TRACE_FUNCTION_FLAGS_ARGS1(...) _PW_TRACE_DISABLED(__VA_ARGS__)
 #endif  // defined(PW_TRACE_TYPE_DURATION_START) &&
         // defined(PW_TRACE_TYPE_DURATION_END)
 
@@ -296,6 +304,10 @@
   _PW_TRACE_SCOPE_ARGS3(PW_TRACE_FLAGS, PW_TRACE_FUNCTION_LABEL, group)
 #define _PW_TRACE_FUNCTION_FLAGS_ARGS2(flag, group) \
   _PW_TRACE_SCOPE_ARGS3(flag, PW_TRACE_FUNCTION_LABEL, group)
+#else  // PW_TRACE_TYPE_DURATION_GROUP_END
+#define _PW_TRACE_SCOPE_ARGS3(...) _PW_TRACE_DISABLED(__VA_ARGS__)
+#define _PW_TRACE_FUNCTION_ARGS1(...) _PW_TRACE_DISABLED(__VA_ARGS__)
+#define _PW_TRACE_FUNCTION_FLAGS_ARGS2(...) _PW_TRACE_DISABLED(__VA_ARGS__)
 #endif  // defined(PW_TRACE_TYPE_DURATION_GROUP_START) &&
         // defined(PW_TRACE_TYPE_DURATION_GROUP_END)
 
@@ -322,6 +334,10 @@
       PW_TRACE_FLAGS, PW_TRACE_FUNCTION_LABEL, group, trace_id)
 #define _PW_TRACE_FUNCTION_FLAGS_ARGS3(flag, group, trace_id) \
   _PW_TRACE_SCOPE_ARGS4(flag, PW_TRACE_FUNCTION_LABEL, group, trace_id)
+#else  // PW_TRACE_TYPE_DURATION_GROUP_END
+#define _PW_TRACE_SCOPE_ARGS4(...) _PW_TRACE_DISABLED(__VA_ARGS__)
+#define _PW_TRACE_FUNCTION_ARGS2(...) _PW_TRACE_DISABLED(__VA_ARGS__)
+#define _PW_TRACE_FUNCTION_FLAGS_ARGS3(...) _PW_TRACE_DISABLED(__VA_ARGS__)
 #endif  // defined(PW_TRACE_TYPE_ASYNC_START) &&
         // defined(PW_TRACE_TYPE_ASYNC_END)
 
diff --git a/pw_trace/pw_trace_zero/public_overrides/pw_trace_backend/trace_backend.h b/pw_trace/pw_trace_zero/public_overrides/pw_trace_backend/trace_backend.h
new file mode 100644
index 000000000..a79d49b99
--- /dev/null
+++ b/pw_trace/pw_trace_zero/public_overrides/pw_trace_backend/trace_backend.h
@@ -0,0 +1,20 @@
+// Copyright 2022 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+//==============================================================================
+//
+#pragma once
+
+// No backend is included so that all backend macros are left undefined.  This
+// is primarily used to test that `trace.h` compiles without warnings when
+// using a backend that does not implement certain macros.