Implement TR31_USE_SSCANF_DATETIME

This CMake option and C preprocessor definition ensures that sscanf()
will be used for date/time parsing even when strptime() is available. It
also makes it much easier to test the sscanf() date/time parsing.

Author: leonlynch

.github/workflows/ubuntu-build.yaml

@@ -42,6 +42,34 @@ jobs:
     - name: Test
       run: ctest --test-dir build --output-on-failure
 
+  build-ubuntu-sscanf:
+    name: Ubuntu (sscanf)
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Install dependencies
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y libmbedtls-dev
+
+    - name: Checkout
+      uses: actions/checkout@v4
+      with:
+        submodules: recursive
+    - run: git describe --always --dirty
+
+    - name: Configure CMake with sscanf() for date/time
+      run: |
+        cmake -B build \
+          -DCMAKE_BUILD_TYPE="Debug" \
+          -DTR31_USE_SSCANF_DATETIME=ON
+
+    - name: Build
+      run: cmake --build build -j 4
+
+    - name: Test
+      run: ctest --test-dir build --output-on-failure -j 4
+
   build-ubuntu-legacy-release:
     strategy:
       fail-fast: false

src/CMakeLists.txt

@@ -93,6 +93,14 @@ else()
 	# set as cache entry to persist across multiple builds
 	set(TR31_ENABLE_DATETIME_CONVERSION OFF CACHE INTERNAL "Date/time conversion availability")
 endif()
+# option to use sscanf() for date/time parsing even when strptime() is
+# available
+option(TR31_USE_SSCANF_DATETIME "Use sscanf() for date/time parsing")
+if(HAVE_STRPTIME AND NOT TR31_USE_SSCANF_DATETIME)
+	message(STATUS "Using strptime() for date/time parsing")
+else()
+	message(STATUS "Using sscanf() for date/time parsing")
+endif()
 
 include(GNUInstallDirs) # provides CMAKE_INSTALL_* variables and good defaults for install()
 

src/tr31_config.h.in

@@ -33,5 +33,6 @@
 #cmakedefine HAVE_TIMEGM
 #cmakedefine HAVE_MKGMTIME
 #cmakedefine TR31_ENABLE_DATETIME_CONVERSION
+#cmakedefine TR31_USE_SSCANF_DATETIME
 
 #endif

src/tr31_strings.c

@@ -40,7 +40,7 @@
 #ifdef HAVE_TIME_H
 #include <time.h>
 #endif
-#ifndef HAVE_STRPTIME
+#if !defined(HAVE_STRPTIME) || defined(TR31_USE_SSCANF_DATETIME)
 #include <stdio.h> // For sscanf()
 #endif
 #endif // TR31_ENABLE_DATETIME_CONVERSION
@@ -512,7 +512,7 @@ static int tr31_opt_block_iso8601_get_string(const struct tr31_opt_ctx_t* opt_bl
 {
 #ifdef TR31_ENABLE_DATETIME_CONVERSION
 	char* iso8601_str;
-#ifdef HAVE_STRPTIME
+#if defined(HAVE_STRPTIME) && !defined(TR31_USE_SSCANF_DATETIME)
 	char* ptr;
 #else
 	int r;
@@ -537,7 +537,7 @@ static int tr31_opt_block_iso8601_get_string(const struct tr31_opt_ctx_t* opt_bl
 	// See ANSI X9.143:2021, 6.3.6.13, table 21
 	// See ANSI X9.143:2021, 6.3.6.14, table 22
 	memset(&ztm, 0, sizeof(ztm));
-#ifdef HAVE_STRPTIME
+#if defined(HAVE_STRPTIME) && !defined(TR31_USE_SSCANF_DATETIME)
 	switch (opt_block->data_length) {
 		case 0x13 - 4: // YYYYMMDDhhmmssZ
 			ptr = strptime(iso8601_str, "%Y%m%d%H%M%SZ", &ztm);