feat: enable strict compilation with maximum warnings as errors

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ on:
 env:
   VCPKG_BINARY_SOURCES: "clear;x-gha,readwrite"
   SCCACHE_DIR: /home/runner/.cache/sccache
-  CLANG_VERSION: "20"
+  CLANG_VERSION: "22"
 
 jobs:
   # ── Windows: MSVC + clang-cl ──────────────────────────────────────────
@@ -65,13 +65,16 @@ jobs:
           key: apt-compilers-${{ matrix.preset }}-${{ hashFiles('.github/workflows/ci.yml') }}
           restore-keys: apt-compilers-${{ matrix.preset }}-
 
-      - name: Install GCC 14 and ninja
+      - name: Install GCC 15 and ninja
         if: startsWith(matrix.preset, 'gcc-')
         run: |
           sudo apt-get update -q
-          sudo apt-get install -y gcc-14 g++-14 ninja-build catch2
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 14
-          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 14
+          sudo apt-get install -y software-properties-common
+          sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+          sudo apt-get update -q
+          sudo apt-get install -y gcc-15 g++-15 ninja-build catch2
+          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-15 15
+          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-15 15
 
       - name: Install Clang ${{ env.CLANG_VERSION }} from apt.llvm.org
         if: startsWith(matrix.preset, 'clang-')
@@ -202,13 +205,16 @@ jobs:
           key: apt-qt-${{ hashFiles('.github/workflows/ci.yml') }}
           restore-keys: apt-qt-
 
-      - name: Install GCC 14, ninja, catch2, Qt6 WebSockets
+      - name: Install GCC 15, ninja, catch2, Qt6 WebSockets
         run: |
           sudo apt-get update -q
-          sudo apt-get install -y gcc-14 g++-14 ninja-build catch2 \
+          sudo apt-get install -y software-properties-common
+          sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+          sudo apt-get update -q
+          sudo apt-get install -y gcc-15 g++-15 ninja-build catch2 \
             qt6-base-dev qt6-websockets-dev qt6-tools-dev libgl1-mesa-dev
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 14
-          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 14
+          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-15 15
+          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-15 15
 
       - name: Cache sccache
         uses: actions/cache@v4
@@ -251,12 +257,15 @@ jobs:
           key: apt-valgrind-${{ hashFiles('.github/workflows/ci.yml') }}
           restore-keys: apt-valgrind-
 
-      - name: Install GCC 14, ninja, catch2, valgrind
+      - name: Install GCC 15, ninja, catch2, valgrind
         run: |
           sudo apt-get update -q
-          sudo apt-get install -y gcc-14 g++-14 ninja-build catch2 valgrind
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 14
-          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 14
+          sudo apt-get install -y software-properties-common
+          sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+          sudo apt-get update -q
+          sudo apt-get install -y gcc-15 g++-15 ninja-build catch2 valgrind
+          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-15 15
+          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-15 15
 
       - name: Cache sccache
         uses: actions/cache@v4
@@ -355,7 +364,7 @@ jobs:
               -p1 \
               -j "$(nproc)" \
               -extra-arg=-std=c++23 \
-              -warnings-as-errors='*' \
+              -extra-arg=-warnings-as-errors=* \
               -quiet \
               2>&1 | tee clang-tidy-report.txt
 

.github/workflows/docs.yml

@@ -34,9 +34,12 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get update -q
-          sudo apt-get install -y cmake ninja-build doxygen g++-14
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-14 14
-          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-14 14
+          sudo apt-get install -y software-properties-common
+          sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+          sudo apt-get update -q
+          sudo apt-get install -y cmake ninja-build doxygen g++-15
+          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-15 15
+          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-15 15
 
       - name: Configure (docs target only)
         run: |

.gitignore

@@ -8,3 +8,4 @@
 *.user
 *.suo
 .vs/
+bv-clang/

CMakeLists.txt

@@ -23,6 +23,10 @@ endif()
 option(MORPH_BUILD_QT            "Build Qt6 WebSocket backend and tests" OFF)
 option(MORPH_BUILD_DOCUMENTATION "Build doxygen docs"  OFF)
 option(MORPH_BUILD_CLANG_TIDY   "Enable clang-tidy checks (warnings-as-errors)" OFF)
+option(MORPH_ENABLE_STRICT_COMPILATION
+    "Enable strict compilation: treat all warnings as errors with extra diagnostics"
+    ON
+)
 
 # Both Qt consumers (the WebSocket backend and the forms QML renderer) need
 # Qt6 auto-detected on Windows before their find_package(Qt6 ...) calls run.

cmake/compiler_options.cmake

@@ -1,5 +1,6 @@
 function(apply_warnings target)
     target_compile_options(${target} PRIVATE
+        # ── MSVC ──────────────────────────────────────────────────────────────
         $<$<CXX_COMPILER_ID:MSVC>:
             /W4
             /permissive-
@@ -25,23 +26,16 @@ function(apply_warnings target)
             /w14928     # illegal copy-initialization
             /wd4068     # suppress: unknown pragma (e.g. clang pragmas in shared headers)
         >
-        $<$<STREQUAL:${CMAKE_CXX_COMPILER_ID},Clang>:$<$<BOOL:${MSVC}>:
-            -Wno-c++98-compat
-            -Wno-c++98-compat-pedantic
-            -Wno-pre-c++17-compat
-            -Wno-ctad-maybe-unsupported
-            -Wno-exit-time-destructors
-            -Wno-global-constructors
-            -Wno-shadow-uncaptured-local
-            -Wno-unused-command-line-argument
-        >>
-
-        $<$<CXX_COMPILER_ID:GNU,Clang>:
+        # ── Clang: -Weverything, then subtract the noise ─────────────────────
+        # Enable every warning Clang has (Linux clang and clang-cl alike), so a
+        # compiler upgrade opts us into new diagnostics automatically. The
+        # suppressions below are the *only* categories we turn back off; anything
+        # not listed stays an error under -Werror.
+        $<$<CXX_COMPILER_ID:Clang>:-Weverything>
+        $<$<CXX_COMPILER_ID:GNU>:
             -Wall
             -Wextra
             -Wpedantic
-        >
-        $<$<CXX_COMPILER_ID:Clang>:
             -Wshadow
             -Wnon-virtual-dtor
             -Wold-style-cast
@@ -51,9 +45,129 @@ function(apply_warnings target)
             -Wconversion
             -Wsign-conversion
             -Wmisleading-indentation
-            -Wnull-dereference
             -Wimplicit-fallthrough
         >
+        # -Wnull-dereference: Clang gets it free via -Weverything. On GCC the
+        # optimizer emits false positives from inside libstdc++ (std::function)
+        # at -O2+, and the diagnostic leaks out of the system header (it runs
+        # post-inlining) where -isystem cannot suppress it, and it is a no-op at
+        # -O0 — so it is left off for GCC entirely.
+    )
+
+    # ── Clang -Weverything suppressions (must come *after* -Weverything) ─────
+    target_compile_options(${target} PRIVATE
+        $<$<CXX_COMPILER_ID:Clang>:
+            # (a) Back-compat warnings — irrelevant: we target C++23, so being
+            #     "incompatible with C++98/14/17/20" is the whole point.
+            -Wno-c++98-compat
+            -Wno-c++98-compat-pedantic
+            -Wno-pre-c++14-compat
+            -Wno-pre-c++17-compat
+            -Wno-pre-c++17-compat-pedantic
+            -Wno-pre-c++20-compat
+            -Wno-pre-c++20-compat-pedantic
+            # (b) Inherent to a header-only, templated library.
+            -Wno-weak-vtables               # vtable emitted per TU for inline-virtual classes
+            -Wno-ctad-maybe-unsupported     # CTAD on types without explicit deduction guides
+            -Wno-padded                     # struct tail/inter-member padding
+            -Wno-exit-time-destructors      # function-local statics with non-trivial dtors
+            -Wno-global-constructors        # non-trivial namespace-scope initializers
+            # (c) Stylistic / opinionated noise, not defects.
+            -Wno-missing-noreturn
+            -Wno-nrvo                       # not eliding a trivial-type copy on return
+            -Wno-shadow-uncaptured-local    # lambda param shadowing an uncaptured local
+            -Wno-documentation-unknown-command
+            -Wno-unsafe-buffer-usage        # flags all pointer arithmetic; needs a hardened API
+            -Wno-unsafe-buffer-usage-in-libc-call
+            -Wno-float-equal                # exact == is intentional in the value/rational tests
+            # (d) Conflicts with a warning we deliberately keep.
+            -Wno-covered-switch-default     # collides with -Wswitch-enum + -Wswitch-default
+            # (e) Third-party test macros.
+            -Wno-c2y-extensions             # Catch2 TEST_CASE expands __COUNTER__
+            -Wno-unused-member-function     # Catch2/test-fixture helper members
+            -Wno-unneeded-member-function
+        >
+        # clang-cl only: driver noise from the MSVC-mode command line.
+        $<$<STREQUAL:${CMAKE_CXX_COMPILER_ID},Clang>:$<$<BOOL:${MSVC}>:
+            -Wno-unique-object-duplication
+            -Wno-unused-command-line-argument
+        >>
+    )
+
+    # ── Strict mode: warnings-as-errors + maximum diagnostics ──────────────
+    # Controlled by MORPH_ENABLE_STRICT_COMPILATION (default ON in CI).
+    if(MORPH_ENABLE_STRICT_COMPILATION)
+        target_compile_options(${target} PRIVATE
+            $<$<CXX_COMPILER_ID:GNU,Clang>:-Werror>
+            $<$<CXX_COMPILER_ID:MSVC>:/WX>
+            # Clang needs no extra named flags here — -Weverything (above) already
+            # supersets every one of these. This block is the GCC equivalent of
+            # "-Weverything": the widest practical set, since GCC has no such flag.
+            $<$<CXX_COMPILER_ID:GNU>:
+                # Diagnostics also carried on Clang via -Weverything.
+                -Wcast-qual
+                -Wformat=2
+                -Wredundant-decls
+                -Winit-self
+                -Wmissing-include-dirs
+                -Wundef
+                -Wswitch-default
+                -Wswitch-enum
+                -Wctor-dtor-privacy
+                -Wpacked
+                -Wdouble-promotion
+                -Wformat-security
+                -Wformat-nonliteral
+                -Wmissing-declarations
+                -Warray-bounds
+                # GCC-specific analyses.
+                -Wduplicated-cond
+                -Wduplicated-branches
+                -Wlogical-op
+                -Wuseless-cast
+                -Walloc-zero
+                -Wstringop-truncation
+                -Wsuggest-override
+                -Wsubobject-linkage
+                -Wtrampolines
+                -Wconditionally-supported
+                # Widened set (max diagnostics).
+                -Wstrict-overflow=2
+                -Wformat-overflow=2
+                -Wformat-truncation=2
+                -Wformat-signedness
+                -Wshift-overflow=2
+                -Wstringop-overflow=4
+                # -Wnoexcept is intentionally omitted: it leaks out of libstdc++
+                # <type_traits> when Catch2's (potentially-throwing) test lambdas
+                # are passed to std::is_nothrow_invocable, which is noise from
+                # third-party code, not a defect in ours.
+                -Wnoexcept-type
+                -Wredundant-tags
+                -Wmismatched-tags
+                -Wvolatile
+                -Wzero-as-null-pointer-constant
+                -Wextra-semi
+                -Wsign-promo
+                -Wcatch-value=3
+                -Wplacement-new=2
+                -Wunused-const-variable=2
+                -Wdisabled-optimization
+                -Wenum-conversion
+                -Warith-conversion
+                -Wdate-time
+                -Wattribute-alias=2
+                -Wcast-align=strict
+                -Wunsafe-loop-optimizations
+            >
+        )
+    endif()
+    # ${MSVC} is true for both cl and clang-cl (any compiler targeting the MSVC
+    # runtime), so clang-cl also gets _CRT_SECURE_NO_WARNINGS — its CXX_COMPILER_ID
+    # is "Clang", which the CXX_COMPILER_ID:MSVC genex would miss, leaving CRT
+    # functions like fopen flagged as deprecated under -Werror.
+    target_compile_definitions(${target} PRIVATE
+        $<$<BOOL:${MSVC}>:_CRT_SECURE_NO_WARNINGS>
     )
 endfunction()
 
@@ -81,4 +195,4 @@ function(apply_coverage target)
         -fprofile-instr-generate -fcoverage-mapping -g -O0)
     target_link_options(${target} PRIVATE
         -fprofile-instr-generate)
-endfunction()
+endfunction()

examples/forms/lab_units.hpp

@@ -46,8 +46,8 @@ struct morph::units::UnitTraits<lab::Unit> {
             case lab::Unit::g:         return {"g", "g", 1};
             case lab::Unit::t:         return {"t", "t", 4};
             case lab::Unit::l:         return {"l", "L", 1};
+            default:                   return {"?", "?", 3};
         }
-        return {"?", "?", 3};
     }
 
     /// @brief Within-dimension conversion ratios (mass g/t ↔ kg, volume L ↔ m³).

include/morph/action_log.hpp

@@ -211,7 +211,6 @@ inline void setActionLog(std::shared_ptr<IActionLog> log) {
 /// case's sink never leaks into the next) and for applications that need to
 /// temporarily redirect auto-attached logging within a scope.
 ///
-/// @par Example
 /// @code
 /// {
 ///     morph::journal::ScopedActionLog guard{std::make_shared<morph::journal::InMemoryActionLog>()};

include/morph/backend.hpp

@@ -210,8 +210,8 @@ class LocalBackend : public detail::IBackend {
             }
         }
         for (auto& [modelId, holder] : sinks) {
-            _strand.post(modelId, [holder = std::move(holder)]() mutable {
-                auto* sink = dynamic_cast<::morph::model::detail::IBackendChangedSink*>(holder.get());
+            _strand.post(modelId, [h = std::move(holder)]() mutable {
+                auto* sink = dynamic_cast<::morph::model::detail::IBackendChangedSink*>(h.get());
                 if (sink != nullptr) {
                     sink->onBackendChanged();
                 }

include/morph/datetime.hpp

@@ -301,12 +301,12 @@ template <>
 struct from<JSON, morph::time::DateTime> {
     template <auto Opts>
     static void op(auto&& value, is_context auto&& ctx, auto&& iter, auto end) {
-        std::string text{};
-        parse<JSON>::op<Opts>(text, ctx, iter, end);
+        std::string str{};
+        parse<JSON>::op<Opts>(str, ctx, iter, end);
         if (bool(ctx.error)) [[unlikely]] {
             return;
         }
-        if (auto parsed = morph::time::DateTime::fromIso8601(text); parsed.has_value()) {
+        if (auto parsed = morph::time::DateTime::fromIso8601(str); parsed.has_value()) {
             value = *parsed;
             return;
         }

include/morph/forms.hpp

@@ -240,7 +240,7 @@ constexpr void reconcileDeclaredPrecision(A& action) {
         constexpr auto memberCount = glz::reflect<Plain>::size;
         auto memberTie = glz::to_tie(action);
         [&]<std::size_t... I>(std::index_sequence<I...>) {
-            auto retag = [&]<std::size_t Idx>() {
+            [[maybe_unused]] auto retag = [&]<std::size_t Idx>() {
                 auto& member = glz::get_member(action, get<Idx>(memberTie));
                 using Member = std::remove_cvref_t<decltype(member)>;
                 if constexpr (units::isQuantity<Member>) {

include/morph/logger.hpp

@@ -41,8 +41,9 @@ constexpr std::string_view levelName(LogLevel level) noexcept {
             return "ERROR";
         case LogLevel::off:
             return "OFF  ";
+        default:
+            return "?    ";
     }
-    return "?    ";
 }
 
 /// @brief Sink function type used internally for log output.
@@ -52,11 +53,11 @@ using Logger = std::function<void(LogLevel, std::string_view)>;
 ///        lines (log injection).
 ///
 /// A message is a single logical record; the default sink emits it as one line.
-/// User-controlled text containing `\n`, `\r`, or other C0 control bytes could
+/// User-controlled text containing \n, \r, or other C0 control bytes could
 /// otherwise splice a forged `[ERROR] ...` line into the stream or corrupt a
 /// line-oriented log parser. This replaces CR/LF/TAB with their C-style escapes
-/// (`\n`, `\r`, `\t`) and any remaining control byte (`< 0x20`, or `0x7f` DEL)
-/// with a `\xHH` escape, leaving printable text (including non-ASCII UTF-8
+/// (\n, \r, \t) and any remaining control byte (< 0x20, or 0x7f DEL)
+/// with a \xHH escape, leaving printable text (including non-ASCII UTF-8
 /// continuation bytes `>= 0x80`) untouched. It is a cheap single pass with no
 /// per-byte escaping work on the common (clean) path (just one string copy).
 /// @param msg Raw message to sanitize.
@@ -220,7 +221,6 @@ void logError(std::format_string<Args...> fmt, Args&&... args) {
 /// custom sink into other tests. Thread-safe construction and destruction —
 /// the global mutex is acquired briefly during each.
 ///
-/// @par Example
 /// @code
 /// {
 ///     std::vector<std::string> captured;

include/morph/offline_queue.hpp

@@ -74,11 +74,14 @@ struct IOfflineQueue {
     /// @param payload        Serialised action to persist.
     /// @param idempotencyKey Stable dedup token for the logical op; may be empty.
     /// @return A stable id that can be passed to `markDone()`.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Woverloaded-virtual"
     virtual uint64_t enqueue(std::string payload, std::string idempotencyKey) {
         const uint64_t itemId = enqueue(std::move(payload));
         setIdempotencyKey(itemId, std::move(idempotencyKey));
         return itemId;
     }
+#pragma GCC diagnostic pop
 
     /// @brief Returns all pending items in enqueue order without removing them.
     ///