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+#import "@preview/polylux:0.4.0": *
+#import "@preview/metropolis-polylux:0.1.0" as metropolis
+
+#show: metropolis.setup
+#show: metropolis.setup.with(footer: [Firmware project with Meson build system])
+#show raw: set text(ligatures: false, features: (calt: 0))
+
+#slide[
+  #set page(header: none, footer: none, margin: 3em)
+
+  #text(size: 1.3em)[*Firmware project with Meson build system*]
+
+  Community Over Code Glasgow 2026
+
+  #metropolis.divider
+
+  #set text(size: .8em, weight: "light")
+  Karel Kočí
+
+  13.10.2026
+]
+
+#slide[
+  = The Point
+
+  #set text(size: 0.95em)
+  POSIX gives ability to run same programs on NuttX and Linux.
+
+  Advantages:
+  - Options when selecting libraries
+  - Easier and faster testing (including CI/CD)
+  - Possibility to test with tools such as Valgrind
+
+  Workflow:
+  - Develop on PC including libraries
+  - Unit testing on PC
+  - Sw/sw integration on PC
+  - Sw/hw integration on real hardware
+
+  We need a good way to build project for both targets (for NuttX flat build).
+]
+
+#metropolis.new-section[NuttX external]
+
+#slide[
+  = Standard NuttX
+  ```
+  .
+  ├── nuttx
+  │   └── ...
+  └── apps
+      └── ...
+  ```
+  \
+  ```bash
+  cd nuttx
+  ./tools/configure.sh rv-virt:nsh
+  make
+  ```
+]
+
+#slide[
+  = External Applications and Libraries
+  ```
+  ├── nuttx
+  │   ├── external -> ../project-libs
+  │   └── ...
+  ├── apps
+  │   ├── external -> ../project-apps
+  │   └── ...
+  ├── project-libs
+  │   └── ...
+  └── project-apps
+      └── ...
+  ```
+  #text(weight: "bold")[`configure-nuttx.sh`]
+  ```bash
+    ln -sf ../project-libs nuttx/external
+    ln -sf ../project-apps apps/external
+  ```
+]
+
+#slide[
+  = Apps Directory
+
+  #text(weight: "bold")[`project-apps/Make.defs`]
+  ```make
+    include $(wildcard $(APPDIR)/external/*/Make.defs)
+  ```
+
+  #text(weight: "bold")[`project-apps/Makefile`]
+  ```make
+    MENUDESC = "Project Applications"
+    include $(APPDIR)/Directory.mk
+  ```
+]
+
+#slide[
+  = A Project App
+
+  #text(weight: "bold")[`project-apps/project_hello/Make.defs`]
+  ```make
+    CONFIGURED_APPS += $(APPDIR)/external/project_hello
+  ```
+
+  #text(weight: "bold")[`project-apps/project_hello/Makefile`]
+  ```make
+    include $(APPDIR)/Make.defs
+    PROGNAME  = $(CONFIG_NUTTX_USBNSH_PROGNAME)
+    PRIORITY  = $(CONFIG_NUTTX_USBNSH_PRIORITY)
+    STACKSIZE = $(CONFIG_NUTTX_USBNSH_STACKSIZE)
+    MODULE    = $(CONFIG_NUTTX_USBNSH)
+    MAINSRC = project_hello_main.c
+    include $(APPDIR)/Application.mk
+  ```
+
+  #text(weight: "bold")[`project-apps/project_hello/Kconfig`] ...
+]
+
+#slide[
+  = A Project App: In More Depth
+  #text(size: 0.9em)[
+    ```make
+    all:: .built
+    context::
+    register::
+      $(call REGISTER,$(PROGNAME_$@),$(PRIORITY_$@),$(STACKSIZE_$@),$@_main)
+
+    .built: $(AROBJS)
+        $(call ARLOCK, $(call CONVERT_PATH,$(BIN)), $^)
+
+    CFLAGS += ${DEFINE_PREFIX}main=$(addsuffix _main,$(PROGSYM_$@))
+    ```
+  ]
+]
+
+#slide[
+  = External Board
+
+  ```bash
+  mkdir board
+  cp -r nuttx/boards/risc-v/qemu-rv/rv-virt/{src,include,scripts} board/
+  ```
+
+  #text(weight: "bold")[`board/defconfig`] (replace `CONFIG_ARCH_BOARD*`)
+  ```Kconfig
+    ...
+    CONFIG_ARCH_BOARD_CUSTOM=y
+    CONFIG_ARCH_BOARD_CUSTOM_DIR="../board"
+    CONFIG_ARCH_BOARD_CUSTOM_DIR_RELPATH=y
+    CONFIG_ARCH_BOARD_CUSTOM_NAME="TEMPLATE"
+  ```
+
+  #text(weight: "bold")[`configure-nuttx.sh`]
+  ```bash
+    ...
+    cp -f board/defconfig nuttx/.config
+    make -C nuttx olddefconfig
+  ```
+]
+
+#slide[
+  = Bonus Round: Config verification
+  ```bash
+    while read -r line; do
+      [[ "$cnf" == CONFIG_* ]] || continue
+      if [[ "${line#*=}" == "n" ]]; then
+        if grep -q "^${line%=*}=(y|m)$" nuttx/.config; then
+            echo "Not correctly set: $line" >&2; exit 1
+        fi
+      else
+        if ! grep -qF "$line" nuttx/.config; then
+            echo "Not correctly set: $line" >&2; exit 1
+        fi
+      fi
+    done <"board/defconfig"
+  done
+  ```
+]
+
+#metropolis.new-section[Meson]
+
+#slide[
+  = Requirements for Build System
+  - Build libraries and applications
+  - No special rules in build system for NuttX
+  - Support for external projects with minimal NuttX boilerplate
+]
+
+#slide[
+  = Quick Overview
+
+  Leading build system for building libraries and executables for Linux.
+
+  \
+
+  #text(weight: "bold")[`meson.build`]
+  ```python
+    project('tutorial', 'c')
+    libfoo = library('foo', files('foo.c'),
+          include_directories=include_directories('.'))
+    executable('demo', files('main.c'), dependencies: [libfoo],
+          install: true)
+  ```
+  \
+
+  Outputs ninja or other build systems.
+]
+
+#slide[
+  = Compare with make and cmake
+  #text(size: 0.9em)[
+    #toolbox.side-by-side[
+      #text(weight: "bold")[Make]
+      - 🙂 Generic build system (language)
+      - 😕 Can be tweaked to build almost anything
+      - 😢 Good build systems are complex
+      - 😢 Build targets standardization old and obsolete
+      - 🫣 No standard way to set toolchain
+      - 😕 No standard way to manage build time dependencies
+    ][
+      #text(weight: "bold")[CMake]
+      - 🙂 Generic build system (language)
+      - 😕 Can be tweaked to build almost anything
+      - 😊 Has build target standardization
+      - 😢 Build target standardization is optional
+      - 😊 Toolchain.cmake
+      - 😢 Alternative ways to manage toolchain
+      - 😊 FetchContent
+    ]
+  ]
+]
+#slide[
+  = While Meson...
+  - 😊 Can build only predefined types
+  - 😊 Can't be tweaked that much
+  - 🙃 Not a complete language
+  - 😊 crossfile.ini
+  - 😍 makes it hard to not use standard way
+  - 😊 subprojects with even cmake support
+]
+
+#metropolis.new-section[Meson Integration]
+
+#slide[
+  = Two Ways
+  #toolbox.side-by-side[
+    #text(weight: "bold")[NuttX as project's library]
+
+    Use exported libraries and linker script from NuttX in any other build
+    system.
+
+    ```bash
+    make -C nuttx export
+    ```
+  ][
+    #text(weight: "bold")[Project as app in NuttX]
+
+    NuttX build system deals with Firmware build.
+
+    App integration uses our project's build system and adds results to NuttX
+    linkage.
+  ]
+]
+
+#slide[
+  = Phase 1: crossfile
+  #text(size: 0.8em)[
+    #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+    ```make
+      crossfile.ini: .FORCE
+        ./crossfile.sh '$(CC)' '$(AR)' '$(CFLAGS)'
+    ```
+    #text(weight: "bold")[`project-apps/meson-apps/crossfile.sh`]
+    ```bash
+      march="${3/*-march=/}"; march="${march/ */}"
+      flags_sanit() { sed -E "s#-Wshadow##;s#\"##g; s#-I #-I#g" <<<"$1" }
+      cat >crossfile.ini <<-EOF
+        [binaries]
+        c = '$1'
+        ar = '$2'
+        [built-in options]
+        c_args = [$(flags_sanit "$cflags" | sed -E "s#([^ ]+)#'\1'#g; s# +#, #g")]
+        c_link_args = ['-nostdlib', '-static', '-r']
+        [host_machine]
+        system = 'nuttx'
+        cpu_family = '${1%%-*}'
+        cpu = '${march}'
+      EOF
+    ```
+  ]
+]
+#slide[
+  = Phase 1.1: Toolchain.cmake
+  #text(weight: "bold")[`project-apps/meson-apps/crossfile.sh`]
+  ```bash
+    cat >>crossfile.ini <<-EOF
+      [properties]
+      cmake_toolchain_file = '$(pwd)/Toolchain.cmake'
+    EOF
+    cat >Toolchain.cmake <<-EOF
+      add_compile_options($(flags_sanit "$cflags"))
+      add_link_options(-nostdlib -static -r)
+    EOF
+  ```
+]
+
+#slide[
+  = Phase 2: context
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    context:: build/build.ninja
+    build/build.ninja: crossfile.ini meson-setup.sh
+      ./meson-setup.sh
+  ```
+  #text(weight: "bold")[`project-apps/meson-apps/meson-setup.sh`]
+  ```bash
+    meson setup --default-library static -Db_staticpic=false \
+      --backend ninja --cross-file crossfile.ini build ../..
+  ```
+]
+
+#slide[
+  = Phase 3: build / build.ninja.mk
+  #text(size: 0.8em)[
+    #text(weight: "bold")[`project-apps/meson-apps/meson-setup.sh`]
+    ```make
+      {
+        meson introspect --targets "build" |
+          jq -r '.[]
+              | select((.type == "static library" or .type == "executable") and .installed)
+              | .name, .filename[0], .type' |
+          while read -r name && read -r file && read -r type; do
+            target="${file#"$sdir/build/"}"
+            if [[ "$type" == "executable" ]]; then
+              echo "\$(eval \$(call EXECUTABLE,$target,$name,${name//-/_}_main))"
+            else
+              echo "\$(eval \$(call STATIC_LIBRARY,$target))"
+            fi
+          done
+        meson introspect --buildsystem-files build | jq -r '.[]' |
+          sed 's#^#build/build.ninja: #'
+      } >"build.ninja.mk"
+    ```
+  ]
+]
+
+#slide[
+  = Phase 3.1: built
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    all:: .built
+      @
+
+    .built: build.ninja.mk $(BUILDS)
+      touch $@
+  ```
+]
+
+#slide[
+  = Phase 3.2: build NINJA_TARGET
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    define NINJA_TARGET
+
+    .NOTPARALLEL: build/$(1)
+    build/$(1): build/build.ninja .FORCE
+      flock build ninja $$(if $$(V),,--quiet) -C build $(1)
+
+    endef
+  ```
+]
+
+#slide[
+  = Phase 3.3: build STATIC_LIBRARY
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    define STATIC_LIBRARY
+    BUILDS += build/$(1).built
+    LIBRARIES += build/$(1)
+    $(call NINJA_TARGET,$(1))
+    build/$(1).built: build/$(1)
+      mkdir -p build/$(1).a
+      $$(UNAR) --output build/$(1).a build/$(1)
+      cd build/$(1).a && for f in *.o; do mv "$$$$f" "$(subst $(DELIM),.,$(1))_$$f"; done
+      $$(call ARLOCK, $$(call CONVERT_PATH,$$(BIN)), build/$(1).a/*)
+      $$(call DELDIR, build/$(1).a)
+      touch $$@
+    endef
+  ```
+]
+
+#slide[
+  = Phase 3.4: libsyms
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    libsyms: $(LIBRARIES)
+      $(NM) --quiet --just-symbols --defined-only $^ | sort -u > $@
+  ```
+]
+
+#slide[
+  = Phase 3.5: register EXECUTABLE
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    define EXECUTABLE
+
+    register:: $$(BUILTIN_REGISTRY)$$(DELIM)$(2).bdat
+
+    $$(BUILTIN_REGISTRY)$$(DELIM)$(2).bdat: build/build.ninja
+      $$(call REGISTER,$(2),$$(PRIORITY),$$(STACKSIZE),$(3))
+
+    endef
+  ```
+]
+
+#slide[
+  = Phase 3.5: build EXECUTABLE
+  #text(weight: "bold")[`project-apps/meson-apps/Makefile`]
+  ```make
+    define EXECUTABLE
+      BUILDS += build/$(1).built
+      $(call NINJA_TARGET,$(1))
+      build/$(1).built: build/$(1) libsyms
+        $$(NM) --quiet --just-symbols --defined-only build/$(1) \
+          | sort -u | comm -2 - libsyms >build/$(1).syms
+        $$(OBJCOPY) --redefine-sym main=$(3) \
+          --localize-symbols=build/$(1).syms \
+          --weaken-symbols=libsyms \
+          build/$(1) build/$(1).o
+        $$(call ARLOCK, $$(call CONVERT_PATH,$$(BIN)), build/$(1).o)
+        touch $$@
+
+  ```
+]
+
+#slide[
+  #show: metropolis.focus
+
+  Demonstration
+]
+
+#slide[
+  = LTO
+  With LTO we can't modify symbols.
+
+  Workaround: add `-flinker-output=nolto-rel` to `c_link_args`
+
+  That removes LTO from linked objects objects (executables).
+
+  LTO not applied to calls from executables to libraries and nuttx.\
+  LTO is still applied to calls between libraries and from libraries to NuttX
+
+]
+
+#slide[
+  = Conclusion
+  Demonstrated possibilities:
+  - How to have project specific applications
+  - How to use off-tree board
+  - How to convince meson to build for NuttX
+  - How to merge meson built files to NuttX
+
+  All this without forking NuttX or Meson.
+
+  Actual implementation provides resiliency against parameters change compared
+  to the examples.
+]
+
+#slide[
+  #show: metropolis.focus
+  Thank you
+
+  Karel Kočí
+
+  #metropolis.divider
+
+  #text(size: 0.6em)[
+    https://gitlab.com/Cynerd/nuttx-meson-template/-/tree/master
+
+    https://gitlab.com/Cynerd/nixos-personal
+
+    https://git.cynerd.cz/presentations/tree/2026-communitycvercode
+  ]
+]