Keep STM32 text conversion compatible with current Arduino cores

.github/workflows/run-unit-tests.yml

@@ -94,6 +94,7 @@ jobs:
         run: |
           python3 -B test/test_companion_usb_default.py
           python3 -B test/test_esp32_usb_serial_hygiene.py
+          python3 -B test/test_stm32_float_conversion.py
 
       - name: Verify message reader buttons, touch targets, and footer layouts
         working-directory: test

src/helpers/TxtDataHelpers.cpp

@@ -118,7 +118,13 @@ static void _ftoa(float f, char *p, int *status)
     *p++ = '0';
   else 
   {
+#if defined(STM32_PLATFORM)
+    // STM32 Arduino exposes utoa, but recent cores no longer declare ltoa.
+    // The sign was emitted above and this magnitude fits a 32-bit unsigned int.
+    utoa(static_cast<unsigned int>(int_part), p, 10);
+#else
     ltoa(int_part, p, 10);
+#endif
     while (*p)
       p++;
   }

test/test_stm32_float_conversion.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""Compile the real text helpers with STM32's utoa-only Arduino API."""
+from pathlib import Path
+import subprocess
+import tempfile
+import unittest
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+class Stm32FloatConversionTest(unittest.TestCase):
+    def test_signed_values_and_limits_without_ltoa(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            (root / "Arduino.h").write_text("""
+#pragma once
+#include <stdlib.h>
+#include <stdio.h>
+inline char* utoa(unsigned int value, char* output, int base) {
+  if (base != 10) abort();
+  sprintf(output, "%u", value);
+  return output;
+}
+""")
+            (root / "test.cpp").write_text("""
+#include <cassert>
+#include <cstring>
+#include "helpers/TxtDataHelpers.h"
+int main() {
+  assert(strcmp(StrHelper::ftoa(0), "0.0") == 0);
+  assert(strcmp(StrHelper::ftoa(1), "1.0") == 0);
+  assert(strcmp(StrHelper::ftoa(-2.5f), "-2.5") == 0);
+  assert(strcmp(StrHelper::ftoa(62.5f), "62.5") == 0);
+  assert(strcmp(StrHelper::ftoa(1.125f), "1.125") == 0);
+  assert(strcmp(StrHelper::ftoa(2147483520.0f), "2147483520.0") == 0);
+  assert(strcmp(StrHelper::ftoa(-2147483520.0f), "-2147483520.0") == 0);
+  assert(strcmp(StrHelper::ftoa(2147483648.0f), "0") == 0);
+  assert(strcmp(StrHelper::ftoa(1e-12f), "0") == 0);
+}
+""")
+            binary = root / "test"
+            subprocess.run(["g++", "-std=c++17", "-DSTM32_PLATFORM", "-I", str(root),
+                            "-I", str(ROOT / "src"), str(root / "test.cpp"),
+                            str(ROOT / "src/helpers/TxtDataHelpers.cpp"), "-o", str(binary)], check=True)
+            subprocess.run([str(binary)], check=True)
+
+
+if __name__ == "__main__":
+    unittest.main()