Closes #16

changelog.md

@@ -10,6 +10,13 @@ existing Git tag; subsequent changes are listed as unreleased.
 
 #### Added
 
+- Issue #16: construction-time validation for both manual runtime definitions and
+  `DbcDecodeBuilder` input: normalized CAN IDs, duplicate keys, signal lengths and
+  positions, enums, finite numeric parameters, ordered ranges, selectors, branch
+  ranges, and overlaps.
+- Regression tests for both construction paths, numeric and bit boundaries,
+  mixed byte orders, exclusive overlaps, mutable input aliases, and failed reloads.
+
 - `FrameDecodeStatus` distinguishes unknown frames, insufficient payloads,
   signal errors, and successful decoding; frame `valid` still means matched.
 - `SignalDecodeStatus::PhysicalConversionFailed` reports NaN/Inf results,
@@ -20,6 +27,15 @@ existing Git tag; subsequent changes are listed as unreleased.
 
 #### Changed
 
+- Runtime construction rejects invalid definitions with `std::invalid_argument`
+  before publishing a snapshot. Decoder tests now expect construction failures
+  for malformed definitions; finite arithmetic overflow remains a decode status.
+- Shared overflow-safe layout validation across parsing, construction, and
+  decoding. Intel extraction also widens bit coordinates before arithmetic.
+- `DecodeDatabase` now accepts definitions by const reference and copies them,
+  even for rvalues, preventing retained
+  mutable aliases from modifying the frozen snapshot or invalidating its index.
+
 - Short payloads decode available signals without padding; longer payloads
   ignore bytes beyond the declared DLC. Short frame status takes precedence
   over signal errors, with per-signal causes retained in definition order.