From 04824b639847ea2bcf4920b0d8b9eeb62f142245 Mon Sep 17 00:00:00 2001
From: Scott James Remnant <keybuk@google.com>
Date: Thu, 28 Apr 2022 17:27:08 -0700
Subject: [PATCH] pw_protobuf: Allow copying of const callbacks

This fixes a bug where it wasn't possible to copy a const message
structure, the callback was intended to be "copyable as empty" but was
missing a 'const' in the right place.

Change-Id: I109d14ec16a5dcc7845654113419036ee6007117
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/92760
Pigweed-Auto-Submit: Scott James Remnant <keybuk@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
---
 pw_protobuf/codegen_message_test.cc           | 34 +++++++++++++++++++
 .../public/pw_protobuf/internal/codegen.h     |  2 +-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/pw_protobuf/codegen_message_test.cc b/pw_protobuf/codegen_message_test.cc
index e39939ef7..f6d84bfd4 100644
--- a/pw_protobuf/codegen_message_test.cc
+++ b/pw_protobuf/codegen_message_test.cc
@@ -205,6 +205,40 @@ TEST(CodegenMessage, Inequality) {
   EXPECT_FALSE(one == two);
 }
 
+TEST(CodegenMessage, ConstCopyable) {
+  const Pigweed::Message one{
+      .magic_number = 0x49u,
+      .ziggy = -111,
+      .cycles = 0x40302010fecaaddeu,
+      .ratio = -1.42f,
+      .error_message = "not a typewriter",
+      .pigweed = {.status = Bool::FILE_NOT_FOUND},
+      .bin = Pigweed::Protobuf::Binary::ZERO,
+      .proto = {.bin = Proto::Binary::OFF,
+                .pigweed_pigweed_bin = Pigweed::Pigweed::Binary::ZERO,
+                .pigweed_protobuf_bin = Pigweed::Protobuf::Binary::ZERO,
+                .meta =
+                    {
+                        .file_name = "/etc/passwd",
+                        .status = Pigweed::Protobuf::Compiler::Status::FUBAR,
+                        .protobuf_bin = Pigweed::Protobuf::Binary::ONE,
+                        .pigweed_bin = Pigweed::Pigweed::Binary::ONE,
+                    }},
+      .data = {std::byte{0x10},
+               std::byte{0x20},
+               std::byte{0x30},
+               std::byte{0x40},
+               std::byte{0x50},
+               std::byte{0x60},
+               std::byte{0x70},
+               std::byte{0x80}},
+      .bungle = -111,
+  };
+  Pigweed::Message two = one;
+
+  EXPECT_TRUE(one == two);
+}
+
 PW_MODIFY_DIAGNOSTICS_POP();
 
 TEST(CodegenMessage, Read) {
diff --git a/pw_protobuf/public/pw_protobuf/internal/codegen.h b/pw_protobuf/public/pw_protobuf/internal/codegen.h
index 5d4287c7b..3f6cf2dd5 100644
--- a/pw_protobuf/public/pw_protobuf/internal/codegen.h
+++ b/pw_protobuf/public/pw_protobuf/internal/codegen.h
@@ -167,7 +167,7 @@ union Callback {
   constexpr Callback& operator=(Callback&& other) = default;
 
   // Copying a callback does not copy the functions.
-  constexpr Callback(Callback&) : encode_() {}
+  constexpr Callback(const Callback&) : encode_() {}
   constexpr Callback& operator=(const Callback&) {
     encode_ = nullptr;
     return *this;