fix(c): tolerate null pointers for empty list arguments

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- **C/C++ SDKs:** every list argument that crosses the FFI boundary now tolerates a null pointer with a zero length. `std::vector::data()` is allowed to return `nullptr` for an empty vector, which is exactly what the C++ binding passes for an omitted list argument, but the C layer fed it straight to `std::slice::from_raw_parts` — undefined behaviour that **aborts the process** under the debug UB checks. Hit live by `QuoteContext::warrant_list` with no filters (`c/src/quote_context/context.rs`); all 17 call sites across `quote_context`, `trade_context`, `agent_context`, `alert_context`, and `types` now go through a null-tolerant `slice_from_raw_parts` helper
+
 ### Added
 
 - **Rust:** `Signal.status` is now a `SignalStatus` enum (pending / active / deleted / ai-failed / filtered-by-manual / ai-submit-failed), `SignalsResponse.total` is `i32` to match the wire contract, and the `risk_level` / `display_control` fields were dropped — neither is part of the API contract nor served in production

c/src/agent_context/context.rs

@@ -13,7 +13,7 @@ use crate::{
     async_call::{CAsyncCallback, execute_async},
     callback::CFreeUserDataFunc,
     config::CConfig,
-    types::{CCow, ToFFI, cstr_to_rust},
+    types::{CCow, ToFFI, cstr_to_rust, slice_from_raw_parts},
 };
 
 /// AI Agent conversation context
@@ -65,10 +65,10 @@ unsafe fn answers_from_ffi(
     num_answers: usize,
 ) -> AnswersByToolCall {
     let mut map: AnswersByToolCall = HashMap::new();
-    for entry in std::slice::from_raw_parts(answers, num_answers) {
+    for entry in slice_from_raw_parts(answers, num_answers) {
         let tool_call_id = cstr_to_rust(entry.tool_call_id);
         let mut questions = HashMap::new();
-        for qa in std::slice::from_raw_parts(entry.answers, entry.num_answers) {
+        for qa in slice_from_raw_parts(entry.answers, entry.num_answers) {
             questions.insert(cstr_to_rust(qa.question), cstr_to_rust(qa.answer));
         }
         map.insert(tool_call_id, questions);

c/src/alert_context/types.rs

@@ -2,7 +2,7 @@ use std::os::raw::c_char;
 
 use longbridge::alert::{AlertItem, AlertList, AlertSymbolGroup};
 
-use crate::types::{CString, CVec, ToFFI};
+use crate::types::{CString, CVec, ToFFI, slice_from_raw_parts};
 
 /// A single alert indicator configuration for a symbol.
 #[repr(C)]
@@ -63,7 +63,7 @@ impl CAlertItem {
     /// `state` pointer must point to at least `num_state` valid `i32` values.
     pub unsafe fn to_alert_item(&self) -> longbridge::alert::AlertItem {
         use crate::types::cstr_to_rust;
-        let state = std::slice::from_raw_parts(self.state, self.num_state).to_vec();
+        let state = slice_from_raw_parts(self.state, self.num_state).to_vec();
         let value_map_str = cstr_to_rust(self.value_map);
         let value_map = serde_json::from_str(&value_map_str).unwrap_or(serde_json::Value::Null);
         longbridge::alert::AlertItem {

c/src/quote_context/context.rs

@@ -33,7 +33,10 @@ use crate::{
             LB_WATCHLIST_GROUP_NAME, LB_WATCHLIST_GROUP_SECURITIES,
         },
     },
-    types::{CCow, CDate, CDateTime, CMarket, CVec, ToFFI, cstr_array_to_rust, cstr_to_rust},
+    types::{
+        CCow, CDate, CDateTime, CMarket, CVec, ToFFI, cstr_array_to_rust, cstr_to_rust,
+        slice_from_raw_parts,
+    },
 };
 
 pub type COnQuoteCallback = extern "C" fn(*const CQuoteContext, *const CPushQuote, *mut c_void);
@@ -781,23 +784,23 @@ pub unsafe extern "C" fn lb_quote_context_warrant_list(
     let symbol = cstr_to_rust(symbol);
     let sort_by = sort_by.into();
     let sort_order = sort_order.into();
-    let warrant_type = std::slice::from_raw_parts(warrant_type, num_warrant_type)
+    let warrant_type = slice_from_raw_parts(warrant_type, num_warrant_type)
         .iter()
         .copied()
         .map(Into::into)
         .collect::<Vec<_>>();
-    let issuer = std::slice::from_raw_parts(issuer, num_issuer).to_vec();
-    let expiry_date = std::slice::from_raw_parts(expiry_date, num_expiry_date)
+    let issuer = slice_from_raw_parts(issuer, num_issuer).to_vec();
+    let expiry_date = slice_from_raw_parts(expiry_date, num_expiry_date)
         .iter()
         .copied()
         .map(Into::into)
         .collect::<Vec<_>>();
-    let price_type = std::slice::from_raw_parts(price_type, num_price_type)
+    let price_type = slice_from_raw_parts(price_type, num_price_type)
         .iter()
         .copied()
         .map(Into::into)
         .collect::<Vec<_>>();
-    let status = std::slice::from_raw_parts(status, num_status)
+    let status = slice_from_raw_parts(status, num_status)
         .iter()
         .copied()
         .map(Into::into)
@@ -904,7 +907,7 @@ pub unsafe extern "C" fn lb_quote_context_calc_indexes(
 ) {
     let ctx_inner = (*ctx).ctx.clone();
     let symbols = cstr_array_to_rust(symbols, num_symbols);
-    let indexes = std::slice::from_raw_parts(indexes, num_indexes)
+    let indexes = slice_from_raw_parts(indexes, num_indexes)
         .iter()
         .map(|index| (*index).into())
         .collect::<Vec<_>>();
@@ -939,7 +942,7 @@ pub unsafe extern "C" fn lb_quote_context_create_watchlist_group(
 ) {
     let ctx_inner = (*ctx).ctx.clone();
     let name = cstr_to_rust(req.name);
-    let securities = std::slice::from_raw_parts(req.securities, req.num_securities);
+    let securities = slice_from_raw_parts(req.securities, req.num_securities);
     let securities = (req.num_securities > 0).then(|| {
         securities
             .iter()
@@ -1003,7 +1006,7 @@ pub unsafe extern "C" fn lb_quote_context_update_watchlist_group(
     let ctx_inner = (*ctx).ctx.clone();
     let id = req.id;
     let name = ((req.flags & LB_WATCHLIST_GROUP_NAME) != 0).then(|| cstr_to_rust(req.name));
-    let securities = std::slice::from_raw_parts(req.securities, req.num_securities);
+    let securities = slice_from_raw_parts(req.securities, req.num_securities);
     let securities = ((req.flags & LB_WATCHLIST_GROUP_SECURITIES) != 0).then(|| {
         securities
             .iter()

c/src/trade_context/context.rs

@@ -32,7 +32,7 @@ use crate::{
             CSubmitMultiLegOrderOptions, CSubmitOrderOptions, CSubmitOrderResponseOwned,
         },
     },
-    types::{CCow, CVec, ToFFI, cstr_array_to_rust, cstr_to_rust},
+    types::{CCow, CVec, ToFFI, cstr_array_to_rust, cstr_to_rust, slice_from_raw_parts},
 };
 
 pub type COnOrderChangedCallback =
@@ -221,7 +221,7 @@ pub unsafe extern "C" fn lb_trade_context_subscribe(
     userdata: *mut c_void,
 ) {
     let ctx_inner = (*ctx).ctx.clone();
-    let topics = std::slice::from_raw_parts(topics, num_topics)
+    let topics = slice_from_raw_parts(topics, num_topics)
         .iter()
         .copied()
         .map(Into::into)
@@ -240,7 +240,7 @@ pub unsafe extern "C" fn lb_trade_context_unsubscribe(
     userdata: *mut c_void,
 ) {
     let ctx_inner = (*ctx).ctx.clone();
-    let topics = std::slice::from_raw_parts(topics, num_topics)
+    let topics = slice_from_raw_parts(topics, num_topics)
         .iter()
         .copied()
         .map(Into::into)
@@ -366,7 +366,7 @@ pub unsafe extern "C" fn lb_trade_context_history_orders(
             opts2 = opts2.symbol(cstr_to_rust((*opts).symbol));
         }
         if !(*opts).status.is_null() {
-            let status = std::slice::from_raw_parts((*opts).status, (*opts).num_status);
+            let status = slice_from_raw_parts((*opts).status, (*opts).num_status);
             opts2 = opts2.status(status.iter().copied().map(Into::into));
         }
         if !(*opts).side.is_null() {
@@ -409,7 +409,7 @@ pub unsafe extern "C" fn lb_trade_context_today_orders(
             opts2 = opts2.symbol(cstr_to_rust((*opts).symbol));
         }
         if !(*opts).status.is_null() {
-            let status = std::slice::from_raw_parts((*opts).status, (*opts).num_status);
+            let status = slice_from_raw_parts((*opts).status, (*opts).num_status);
             opts2 = opts2.status(status.iter().copied().map(Into::into));
         }
         if !(*opts).side.is_null() {
@@ -638,7 +638,7 @@ pub unsafe extern "C" fn lb_trade_context_submit_multileg(
     let order_type = (*opts).order_type.into();
     let submitted_quantity = (*(*opts).submitted_quantity).value;
     let strategy = (*opts).strategy.into();
-    let legs = std::slice::from_raw_parts((*opts).legs, (*opts).num_legs)
+    let legs = slice_from_raw_parts((*opts).legs, (*opts).num_legs)
         .iter()
         .map(|leg| {
             SubmitMultiLegOrderLeg::new(cstr_to_rust(leg.symbol), (*leg.ratio_quantity).value)

c/src/types/mod.rs

@@ -82,8 +82,24 @@ pub(crate) unsafe fn cstr_to_rust(value: *const c_char) -> String {
         .expect("invalid cstr")
 }
 
+/// Like [`std::slice::from_raw_parts`], but tolerates a null `data` pointer
+/// when `len` is `0`.
+///
+/// `from_raw_parts` requires a non-null, aligned pointer even for a zero-length
+/// slice, but `std::vector::data()` in C++ is allowed to return `nullptr` for
+/// an empty vector — which is exactly what the C++ binding passes for an
+/// omitted list argument. Calling `from_raw_parts(null, 0)` is undefined
+/// behaviour and aborts the process under the debug UB checks.
+pub(crate) unsafe fn slice_from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
+    if len == 0 || data.is_null() {
+        &[]
+    } else {
+        std::slice::from_raw_parts(data, len)
+    }
+}
+
 pub(crate) unsafe fn cstr_array_to_rust(values: *const *const c_char, n: usize) -> Vec<String> {
-    std::slice::from_raw_parts(values, n)
+    slice_from_raw_parts(values, n)
         .iter()
         .copied()
         .map(|value| cstr_to_rust(value))