CI can protect us from loss of precision (#424)

.github/workflows/build-firmware.yaml

@@ -303,6 +303,10 @@ jobs:
     - name: Build Firmware
       run: bash misc/jenkins/compile_other_versions/compile.sh ${{matrix.folder}} ${{matrix.build-target}}
 
+    - name: Check for illegal time conversions
+      working-directory: ./firmware/
+      run: bash check_illegal_conversion.sh
+
     # Build rusEFI console
     - name: Build console
       if: ${{ env.full == 'true' }}

firmware/check_illegal_conversion.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/bash
+
+# Trying to convert float -> long suggests you're probably trying to compute a
+# time period in float, then add it to a timestamp to get some time in the future.
+# If you do this naively, it'll try and do
+# float offset;
+# int64_t stamp;
+# int64_t result = (int64_t)((float)stamp + offset);
+# The resulting loss of precision is unacceptable.
+
+set -euo pipefail
+
+if grep "bl.*<__aeabi_f2lz>" build/fome.list; then
+	echo "Illegal float-to-long conversion detected!"
+	exit 1
+fi