Merge #386: gen: make AccessorType static

c8ca0c0 ci: add -Wmissing-declarations to default.bash (fanquake)
641c78e ci: add -Wmissing-prototypes to LLVM config (fanquake)
52a028c gen: make AccessorType static (fanquake)

Pull request description:

  ```bash
  [4/62] Building CXX object CMakeFiles/mpgen.dir/src/mp/gen.cpp.o
  libmultiprocess/src/mp/gen.cpp:208:13: warning: no previous prototype for function 'AccessorType' [-Wmissing-prototypes]
    208 | std::string AccessorType(kj::StringPtr base_name, const Field& field)
        |             ^
  libmultiprocess/src/mp/gen.cpp:208:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    208 | std::string AccessorType(kj::StringPtr base_name, const Field& field)
        | ^
        | static
  1 warning generated.
  ```

  Used downstream in bitcoin/bitcoin#36743.

ACKs for top commit:
  ryanofsky:
    Code review ACK c8ca0c0. Since last review, just added `-Wmissing-declarations` to the GCC CI config. Thanks!

Tree-SHA512: 249f93a37469b757d712467b5070fb1b2ccd09e43a799eb6bd6c8330cf7a785dfa4f34439f78d3ce426061cb522f6b366a7e33e4fda46f4398dcbe95b1ca90be

Author: ryanofsky

ci/configs/default.bash

@@ -1,5 +1,5 @@
 CI_DESC="CI job using default libraries and tools, and running IWYU"
 CI_DIR=build-default
-export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wundef -Wunused -Wunused-const-variable -Wextra-semi -Wmissing-noreturn -Wtrailing-whitespace"
+export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wundef -Wunused -Wunused-const-variable -Wextra-semi -Wmissing-declarations -Wmissing-noreturn -Wtrailing-whitespace"
 CMAKE_ARGS=(-DMP_ENABLE_IWYU=ON)
 BUILD_ARGS=(-k)

ci/configs/llvm.bash

@@ -2,7 +2,7 @@ CI_DESC="CI job using LLVM-based libraries and tools (clang, libc++, clang-tidy,
 CI_DIR=build-llvm
 NIX_ARGS=(--arg enableLibcxx true)
 export CXX=clang++
-export CXXFLAGS="-Werror -Wall -Wextra -Wextra-semi -Wpedantic -Wundef -Wthread-safety -Wunused -Wunused-const-variable -Wno-c++23-lambda-attributes"
+export CXXFLAGS="-Werror -Wall -Wextra -Wextra-semi -Wmissing-prototypes -Wpedantic -Wundef -Wthread-safety -Wunused -Wunused-const-variable -Wno-c++23-lambda-attributes"
 CMAKE_ARGS=(
   -G Ninja
   -DMP_ENABLE_CLANG_TIDY=ON

src/mp/gen.cpp

@@ -205,7 +205,7 @@ struct FieldList
     }
 };
 
-std::string AccessorType(kj::StringPtr base_name, const Field& field)
+static std::string AccessorType(kj::StringPtr base_name, const Field& field)
 {
     const auto& f = field.param_is_set ? field.param : field.result;
     const auto field_name = f.getProto().getName();