Remove dead getByTid and free attribute keys on shutdown

- Remove getByTid from OtelContexts and ContextApi (zero callers)
- Free strdup'd _attribute_keys in ContextApi::shutdown()

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: jbachorik

ddprof-lib/src/main/cpp/context_api.cpp

@@ -57,6 +57,13 @@ void ContextApi::shutdown() {
         OtelContexts::shutdown();
     }
 
+    // Free registered attribute keys
+    for (int i = 0; i < _attribute_key_count; i++) {
+        free(_attribute_keys[i]);
+        _attribute_keys[i] = nullptr;
+    }
+    _attribute_key_count = 0;
+
     __atomic_store_n(&_initialized, false, __ATOMIC_RELEASE);
 }
 
@@ -150,26 +157,6 @@ bool ContextApi::get(u64& span_id, u64& root_span_id) {
     }
 }
 
-bool ContextApi::getByTid(int tid, u64& span_id, u64& root_span_id) {
-    ContextStorageMode mode = __atomic_load_n(&_mode, __ATOMIC_ACQUIRE);
-
-    if (mode == CTX_STORAGE_OTEL) {
-        // In TLS model, cross-thread reads use ProfiledThread's cached record pointer.
-        // The caller (wallClock signal handler) has access to the target thread's
-        // ProfiledThread, but this static API only receives a TID.
-        // For now, fall through to OtelContexts::getByTid which returns false.
-        u64 trace_high, trace_low;
-        if (OtelContexts::getByTid(tid, trace_high, trace_low, span_id)) {
-            root_span_id = trace_low;
-            return true;
-        }
-        return false;
-    } else {
-        span_id = 0;
-        root_span_id = 0;
-        return false;
-    }
-}
 
 void ContextApi::clear() {
     ContextStorageMode mode = __atomic_load_n(&_mode, __ATOMIC_ACQUIRE);

ddprof-lib/src/main/cpp/context_api.h

@@ -106,19 +106,6 @@ class ContextApi {
      */
     static bool get(u64& span_id, u64& root_span_id);
 
-    /**
-     * Read context for a specific thread by TID.
-     *
-     * Used by JVMTI wall-clock sampling where the sampling thread
-     * needs to read another thread's context.
-     *
-     * @param tid Thread ID to read context for
-     * @param span_id Output: the span ID
-     * @param root_span_id Output: the root span ID
-     * @return true if context was successfully read
-     */
-    static bool getByTid(int tid, u64& span_id, u64& root_span_id);
-
     /**
      * Clear context for the current thread.
      */

ddprof-lib/src/main/cpp/otel_context.cpp

@@ -170,12 +170,6 @@ bool OtelContexts::get(u64& trace_id_high, u64& trace_id_low, u64& span_id) {
     return readRecord(thrd->getOtelContextRecord(), trace_id_high, trace_id_low, span_id);
 }
 
-bool OtelContexts::getByTid(int tid, u64& trace_id_high, u64& trace_id_low, u64& span_id) {
-    // Cross-thread read not supported via TID lookup in TLS model.
-    // Callers should use ProfiledThread's cached record pointer directly.
-    return false;
-}
-
 bool OtelContexts::readRecord(OtelThreadContextRecord* record,
                                u64& trace_id_high, u64& trace_id_low, u64& span_id) {
     if (record == nullptr) {

ddprof-lib/src/main/cpp/otel_context.h

@@ -93,12 +93,6 @@ class OtelContexts {
      */
     static bool get(u64& trace_id_high, u64& trace_id_low, u64& span_id);
 
-    /**
-     * Read context for a specific thread by TID.
-     * Uses ProfiledThread's cached record pointer (signal-safe).
-     */
-    static bool getByTid(int tid, u64& trace_id_high, u64& trace_id_low, u64& span_id);
-
     /**
      * Write a single attribute into the current thread's OTEP record.
      * Appends (key_index, length, value) to attrs_data, re-publishes via detach/attach.

doc/architecture/OtelContextStorage.md

@@ -45,7 +45,7 @@ The system uses a feature-flagged approach where the storage mode is selected at
 │    ├─ initialize(args)  → Select mode based on ctxstorage option        │
 │    ├─ set(spanId, rootSpanId)  → Route to appropriate storage           │
 │    ├─ get(spanId, rootSpanId)  → Read from appropriate storage          │
-│    └─ getByTid(tid, ...)       → Read by thread ID (OTEL mode)         │
+│    └─ clear()                  → Clear current thread's context         │
 │         │                                                               │
 │         ├─────────────────────────┬─────────────────────────────────────┤
 │         ▼                         ▼                                     │
@@ -185,7 +185,6 @@ public:
     static void set(u64 span_id, u64 root_span_id);
     static void setOtel(u64 trace_id_high, u64 trace_id_low, u64 span_id);
     static bool get(u64& span_id, u64& root_span_id);
-    static bool getByTid(int tid, u64& span_id, u64& root_span_id);
     static void clear();
 };
 ```
@@ -201,7 +200,6 @@ public:
 
     static void set(u64 trace_id_high, u64 trace_id_low, u64 span_id);
     static bool get(u64& trace_id_high, u64& trace_id_low, u64& span_id);
-    static bool getByTid(int tid, u64& trace_id_high, u64& trace_id_low, u64& span_id);
     static void clear();
 };
 ```
@@ -270,4 +268,4 @@ ddprof-test/src/test/java/com/datadoghq/profiler/context/
 
 2. **Custom Attributes**: Implemented — `attrs_data` supports variable-length key/value pairs per the OTEP specification. `ThreadContext.setContextAttribute()` writes to OTEP record in OTEL mode, falls back to `registerConstant` + `Context.tags[]` in profiler mode.
 
-3. **Cross-thread reads via getByTid**: Currently limited since TLS cannot be accessed from another thread in-process. The cached record pointer in ProfiledThread provides the mechanism.
+3. **Cross-thread reads**: TLS cannot be accessed from another thread in-process. Signal handlers read their own thread's context via `ProfiledThread`'s cached record pointer.