build: add reusable CMake library target for downstream projects

.github/workflows/ci.yml

@@ -195,6 +195,30 @@ jobs:
         run: |
           docker run --rm --volume $(pwd):/note-c/ --workdir /note-c/ --entrypoint ./scripts/run_cppcheck.sh ghcr.io/blues/note_c_ci:latest
 
+  run_macos_unit_tests:
+    runs-on: macos-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Configure
+        run: cmake -B build -DNOTE_C_BUILD_TESTS=ON
+
+      - name: Build
+        run: cmake --build build --parallel $(sysctl -n hw.ncpu)
+
+      # NOTE: ctest is not run here. A subset of tests that rely on FFF
+      # symbol interposition fail on macOS due to two-level namespace
+      # linking. The build step above verifies that all sources and tests
+      # compile and link successfully.
+      #
+      # Even with -Wl,-flat_namespace, intra-library calls within the
+      # note_c dylib are resolved at link time as direct calls, so FFF
+      # fakes in the test executable cannot interpose them. Fully fixing
+      # this would require linking note-c as a static library for tests
+      # or using a different mocking approach on macOS.
+
   publish_ci_image:
     runs-on: ubuntu-latest
     # Make sure unit tests unit tests passed before publishing.

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.20)
+cmake_minimum_required(VERSION 3.21)
 cmake_policy(SET CMP0095 NEW)
 
 if ("${CMAKE_BINARY_DIR}" STREQUAL "${CMAKE_SOURCE_DIR}")
@@ -16,7 +16,7 @@ if(NOT EXISTS ${PROJECT_BINARY_DIR}/.gitignore)
 endif()
 
 option(NOTE_C_BUILD_DOCS "Build docs." OFF)
-option(NOTE_C_BUILD_TESTS "Build tests." ON)
+option(NOTE_C_BUILD_TESTS "Build tests." ${PROJECT_IS_TOP_LEVEL})
 option(NOTE_C_COVERAGE "Compile for test NOTE_C_COVERAGE reporting." OFF)
 option(NOTE_C_LOW_MEM "Build the library tailored for low memory usage." OFF)
 option(NOTE_C_MEM_CHECK "Run tests with Valgrind." OFF)
@@ -27,61 +27,62 @@ option(NOTE_C_SINGLE_PRECISION "Use single precision for JSON floating point num
 option(NOTE_C_HEARTBEAT_CALLBACK "Enable heartbeat callback support." OFF)
 
 set(NOTE_C_SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR})
-add_library(note_c SHARED)
-target_sources(
-    note_c
-    PRIVATE
-        ${NOTE_C_SRC_DIR}/n_atof.c
-        ${NOTE_C_SRC_DIR}/n_b64.c
-        ${NOTE_C_SRC_DIR}/n_cjson.c
-        ${NOTE_C_SRC_DIR}/n_cjson_helpers.c
-        ${NOTE_C_SRC_DIR}/n_cobs.c
-        ${NOTE_C_SRC_DIR}/n_const.c
-        ${NOTE_C_SRC_DIR}/n_ftoa.c
-        ${NOTE_C_SRC_DIR}/n_helpers.c
-        ${NOTE_C_SRC_DIR}/n_hooks.c
-        ${NOTE_C_SRC_DIR}/n_i2c.c
-        ${NOTE_C_SRC_DIR}/n_md5.c
-        ${NOTE_C_SRC_DIR}/n_printf.c
-        ${NOTE_C_SRC_DIR}/n_request.c
-        ${NOTE_C_SRC_DIR}/n_serial.c
-        ${NOTE_C_SRC_DIR}/n_str.c
-)
-target_compile_options(
-    note_c
-    PRIVATE
-        -Wall
-        -Wextra
-        -Wpedantic
-        -Werror
-        -Og
-        -ggdb
-    PUBLIC
-        -m32
-        -mfpmath=sse
-        -msse2
-)
-target_include_directories(
-    note_c
-    PUBLIC ${NOTE_C_SRC_DIR}
-)
-target_link_directories(
-    note_c
-    PUBLIC
-        /lib32
-        /usr/lib32
-        /usr/lib/gcc/x86_64-linux-gnu/12/32
-)
-target_link_options(
-    note_c
-    PUBLIC
-        -m32
-        -Wl,-melf_i386
+
+# Detect whether the system already provides strlcpy/strlcat (macOS, *BSD).
+# When present, we skip the bundled implementations in n_str.c and define
+# guards so note.h doesn't redeclare them (which collides with the platform's
+# fortified macros).
+include(CheckSymbolExists)
+check_symbol_exists(strlcpy "string.h" HAVE_STRLCPY)
+check_symbol_exists(strlcat "string.h" HAVE_STRLCAT)
+
+set(NOTE_C_SOURCES
+    ${NOTE_C_SRC_DIR}/n_atof.c
+    ${NOTE_C_SRC_DIR}/n_b64.c
+    ${NOTE_C_SRC_DIR}/n_cjson.c
+    ${NOTE_C_SRC_DIR}/n_cjson_helpers.c
+    ${NOTE_C_SRC_DIR}/n_cobs.c
+    ${NOTE_C_SRC_DIR}/n_const.c
+    ${NOTE_C_SRC_DIR}/n_ftoa.c
+    ${NOTE_C_SRC_DIR}/n_helpers.c
+    ${NOTE_C_SRC_DIR}/n_hooks.c
+    ${NOTE_C_SRC_DIR}/n_i2c.c
+    ${NOTE_C_SRC_DIR}/n_md5.c
+    ${NOTE_C_SRC_DIR}/n_printf.c
+    ${NOTE_C_SRC_DIR}/n_request.c
+    ${NOTE_C_SRC_DIR}/n_serial.c
 )
+# n_str.c provides weak strlcpy/strlcat. On systems that already have them
+# the file won't compile because the platform headers define these as
+# fortified macros that conflict with the function definitions.
+if(NOT HAVE_STRLCPY OR NOT HAVE_STRLCAT)
+    list(APPEND NOTE_C_SOURCES ${NOTE_C_SRC_DIR}/n_str.c)
+endif()
+# ---------------------------------------------------------------------------
+# note_c_lib — static library for downstream consumers.
+#
+# Projects that include note-c as a submodule can simply do:
+#
+#   add_subdirectory(note-c)
+#   target_link_libraries(my_app PRIVATE note_c_lib)
+#
+# This target carries the include path and platform compile definitions
+# (HAVE_STRLCPY, etc.) but no test flags, 32-bit cross-compile options,
+# or other CI-specific settings.
+# ---------------------------------------------------------------------------
+add_library(note_c_lib STATIC ${NOTE_C_SOURCES})
+target_include_directories(note_c_lib PUBLIC ${NOTE_C_SRC_DIR})
+
+if(HAVE_STRLCPY)
+    target_compile_definitions(note_c_lib PUBLIC HAVE_STRLCPY)
+endif()
+if(HAVE_STRLCAT)
+    target_compile_definitions(note_c_lib PUBLIC HAVE_STRLCAT)
+endif()
 
 if(NOTE_C_LOW_MEM)
     target_compile_definitions(
-        note_c
+        note_c_lib
         PUBLIC
             NOTE_C_LOW_MEM
     )
@@ -90,15 +91,15 @@ else()
     # about an empty translation unit, so we only add it to the build if
     # NOTE_C_LOW_MEM is false.
     target_sources(
-        note_c
+        note_c_lib
         PRIVATE
             ${NOTE_C_SRC_DIR}/n_ua.c
     )
 endif()
 
 if(NOTE_C_NO_LIBC)
     target_link_options(
-        note_c
+        note_c_lib
         PRIVATE
             -nostdlib
             -nodefaultlibs
@@ -108,37 +109,148 @@ endif()
 
 if(NOTE_NODEBUG)
     target_compile_definitions(
-        note_c
+        note_c_lib
         PUBLIC
             NOTE_NODEBUG
     )
 endif()
 
 if(NOTE_C_SHOW_MALLOC)
     target_compile_definitions(
-        note_c
+        note_c_lib
         PUBLIC
             NOTE_C_SHOW_MALLOC
     )
 endif()
 
 if(NOTE_C_SINGLE_PRECISION)
     target_compile_definitions(
-        note_c
+        note_c_lib
         PUBLIC
             NOTE_C_SINGLE_PRECISION
     )
 endif()
 
 if(NOTE_C_HEARTBEAT_CALLBACK)
     target_compile_definitions(
-        note_c
+        note_c_lib
         PUBLIC
             NOTE_C_HEARTBEAT_CALLBACK
     )
 endif()
 
+# ---------------------------------------------------------------------------
+# note_c — shared library used by the unit test harness.
+#
+# This target adds -Werror, 32-bit cross-compile flags (Linux CI), FFF
+# interposition support (macOS), and the NOTE_C_TEST define. It is NOT
+# intended for downstream consumption.
+# ---------------------------------------------------------------------------
 if(NOTE_C_BUILD_TESTS)
+    add_library(note_c SHARED ${NOTE_C_SOURCES})
+    target_include_directories(note_c PUBLIC ${NOTE_C_SRC_DIR})
+
+    if(HAVE_STRLCPY)
+        target_compile_definitions(note_c PUBLIC HAVE_STRLCPY)
+    endif()
+    if(HAVE_STRLCAT)
+        target_compile_definitions(note_c PUBLIC HAVE_STRLCAT)
+    endif()
+
+    target_compile_options(
+        note_c
+        PRIVATE
+            -Wall
+            -Wextra
+            -Wpedantic
+            -Werror
+            -Og
+            -ggdb
+    )
+    # The Linux CI runs tests in 32-bit mode. These flags are x86-specific and
+    # unavailable on Apple toolchains or non-x86 architectures.
+    if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|i[3-6]86")
+        target_compile_options(note_c PUBLIC -m32 -mfpmath=sse -msse2)
+    endif()
+    if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|i[3-6]86")
+        target_link_directories(
+            note_c
+            PUBLIC
+                /lib32
+                /usr/lib32
+                /usr/lib/gcc/x86_64-linux-gnu/12/32
+        )
+        target_link_options(
+            note_c
+            PUBLIC
+                -m32
+                -Wl,-melf_i386
+        )
+    endif()
+    if(APPLE)
+        # Use flat namespace so test fakes (FFF) can interpose library symbols
+        target_link_options(note_c PRIVATE -Wl,-flat_namespace)
+    endif()
+
+    if(NOTE_C_LOW_MEM)
+        target_compile_definitions(
+            note_c
+            PUBLIC
+                NOTE_C_LOW_MEM
+        )
+    else()
+        # This file is empty if NOTE_C_LOW_MEM is defined, which leads to a warning
+        # about an empty translation unit, so we only add it to the build if
+        # NOTE_C_LOW_MEM is false.
+        target_sources(
+            note_c
+            PRIVATE
+                ${NOTE_C_SRC_DIR}/n_ua.c
+        )
+    endif()
+
+    if(NOTE_C_NO_LIBC)
+        target_link_options(
+            note_c
+            PRIVATE
+                -nostdlib
+                -nodefaultlibs
+                LINKER:--no-undefined
+        )
+    endif()
+
+    if(NOTE_NODEBUG)
+        target_compile_definitions(
+            note_c
+            PUBLIC
+                NOTE_NODEBUG
+        )
+    endif()
+
+    if(NOTE_C_SHOW_MALLOC)
+        target_compile_definitions(
+            note_c
+            PUBLIC
+                NOTE_C_SHOW_MALLOC
+        )
+    endif()
+
+    if(NOTE_C_SINGLE_PRECISION)
+        target_compile_definitions(
+            note_c
+            PUBLIC
+                NOTE_C_SINGLE_PRECISION
+        )
+    endif()
+
+    if(NOTE_C_HEARTBEAT_CALLBACK)
+        target_compile_definitions(
+            note_c
+            PUBLIC
+                NOTE_C_HEARTBEAT_CALLBACK
+        )
+    endif()
+
     # Including CTest here rather than in test/CMakeLists.txt allows us to run
     # ctest from the root build directory (e.g. build/ instead of build/test/).
     # We also need to set MEMORYCHECK_COMMAND_OPTIONS before including this.

n_helpers.c

@@ -2403,7 +2403,7 @@ uint32_t NoteMemAvailable(void)
     objHeader *lastObj = NULL;
     static long int maxsize = 35000;
     for (long int i=maxsize; i>=(long int)sizeof(objHeader); i=i-sizeof(objHeader)) {
-        for (long int j=0;; j++) {
+        for (;;) {
             objHeader *thisObj;
             thisObj = (objHeader *) _Malloc(i);
             if (thisObj == NULL) {
@@ -2416,16 +2416,8 @@ uint32_t NoteMemAvailable(void)
     }
 
     // Free the objects backwards
-    long int lastLength = 0;
-    long int lastLengthCount = 0;
     uint32_t total = 0;
     while (lastObj != NULL) {
-        if (lastObj->length != lastLength) {
-            lastLength = lastObj->length;
-            lastLengthCount = 1;
-        } else {
-            lastLengthCount++;
-        }
         objHeader *thisObj = lastObj;
         lastObj = lastObj->prev;
         total += thisObj->length;

n_ua.c

@@ -92,9 +92,9 @@ __attribute__((weak)) void NoteUserAgentUpdate(J *ua)
 */
 /**************************************************************************/
 #if defined(_MSC_VER)
-J *NoteUserAgent()
+J *NoteUserAgent(void)
 #else
-__attribute__((weak)) J *NoteUserAgent()
+__attribute__((weak)) J *NoteUserAgent(void)
 #endif
 {
 

scripts/check_libc_dependencies.sh

@@ -30,6 +30,8 @@ LIBC_WHITELIST=(
     "strchr"
     "strcmp"
     "strlen"
+    "strlcpy"   # bundled in n_str.c; also available in glibc 2.38+
+    "strlcat"   # bundled in n_str.c; also available in glibc 2.38+
     "strncmp"
     "strstr"
     "strtol"    # required by atoi in NoteGenEnvInt