python · pablogsal · Dec 17, 2025 · Dec 17, 2025
@@ -279,6 +279,35 @@ typedef struct {
     size_t count;
 } StackChunkList;
 
+/*
+ * Context for frame chain traversal operations.
+ */
+typedef struct {
+    /* Inputs */
+    uintptr_t frame_addr;           // Starting frame address
+    uintptr_t base_frame_addr;      // Sentinel at bottom (for validation)
+    uintptr_t gc_frame;             // GC frame address (0 if not tracking)
+    uintptr_t last_profiled_frame;  // Last cached frame (0 if no cache)
+    StackChunkList *chunks;         // Pre-copied stack chunks
+
+    /* Outputs */
+    PyObject *frame_info;           // List to append FrameInfo objects
+    uintptr_t *frame_addrs;         // Array of visited frame addresses
+    Py_ssize_t num_addrs;           // Count of addresses collected
+    Py_ssize_t max_addrs;           // Capacity of frame_addrs array
+    uintptr_t last_frame_visited;   // Last frame address visited
+    int stopped_at_cached_frame;    // Whether we stopped at cached frame
+} FrameWalkContext;
+
+/*
+ * Context for code object parsing.
+ */
+typedef struct {
+    uintptr_t code_addr;            // Code object address in remote process
+    uintptr_t instruction_pointer;  // Current instruction pointer
+    int32_t tlbc_index;             // Thread-local bytecode index (free-threading)
+} CodeObjectContext;
+
 /* Function pointer types for iteration callbacks */
 typedef int (*thread_processor_func)(
     RemoteUnwinderObject *unwinder,
@@ -343,10 +372,7 @@ extern long read_py_long(RemoteUnwinderObject *unwinder, uintptr_t address);
 extern int parse_code_object(
     RemoteUnwinderObject *unwinder,
     PyObject **result,
-    uintptr_t address,
-    uintptr_t instruction_pointer,
-    uintptr_t *previous_frame,
-    int32_t tlbc_index
+    const CodeObjectContext *ctx
 );
 
 extern PyObject *make_location_info(
@@ -420,17 +446,7 @@ extern void *find_frame_in_chunks(StackChunkList *chunks, uintptr_t remote_ptr);
 
 extern int process_frame_chain(
     RemoteUnwinderObject *unwinder,
-    uintptr_t initial_frame_addr,
-    StackChunkList *chunks,
-    PyObject *frame_info,
-    uintptr_t base_frame_addr,
-    uintptr_t gc_frame,
-    uintptr_t last_profiled_frame,
-    int *stopped_at_cached_frame,
-    uintptr_t *frame_addrs,
-    Py_ssize_t *num_addrs,
-    Py_ssize_t max_addrs,
-    uintptr_t *out_last_frame_addr
+    FrameWalkContext *ctx
 );
 
 /* Frame cache functions */
@@ -460,12 +476,7 @@ extern int frame_cache_store(
 
 extern int collect_frames_with_cache(
     RemoteUnwinderObject *unwinder,
-    uintptr_t frame_addr,
-    StackChunkList *chunks,
-    PyObject *frame_info,
-    uintptr_t base_frame_addr,
-    uintptr_t gc_frame,
-    uintptr_t last_profiled_frame,
+    FrameWalkContext *ctx,
     uint64_t thread_id);
 
 /* ============================================================================

@@ -76,6 +76,7 @@ cache_tlbc_array(RemoteUnwinderObject *unwinder, uintptr_t code_addr, uintptr_t
         PyErr_SetString(PyExc_RuntimeError, "TLBC array size exceeds maximum limit");
         return 0; // Invalid size
     }
+    assert(tlbc_size > 0 && tlbc_size <= MAX_TLBC_SIZE);
 
     // Allocate and read the entire TLBC array
     size_t array_data_size = tlbc_size * sizeof(void*);
@@ -156,8 +157,11 @@ parse_linetable(const uintptr_t addrq, const char* linetable, int firstlineno, L
     const uint8_t* ptr = (const uint8_t*)(linetable);
     uintptr_t addr = 0;
     int computed_line = firstlineno;  // Running accumulator, separate from output
+    const size_t MAX_LINETABLE_ENTRIES = 65536;
+    size_t entry_count = 0;
 
-    while (*ptr != '\0') {
+    while (*ptr != '\0' && entry_count < MAX_LINETABLE_ENTRIES) {
+        entry_count++;
         uint8_t first_byte = *(ptr++);
         uint8_t code = (first_byte >> 3) & 15;
         size_t length = (first_byte & 7) + 1;
@@ -277,12 +281,9 @@ make_frame_info(RemoteUnwinderObject *unwinder, PyObject *file, PyObject *locati
 int
 parse_code_object(RemoteUnwinderObject *unwinder,
                   PyObject **result,
-                  uintptr_t address,
-                  uintptr_t instruction_pointer,
-                  uintptr_t *previous_frame,
-                  int32_t tlbc_index)
+                  const CodeObjectContext *ctx)
 {
-    void *key = (void *)address;
+    void *key = (void *)ctx->code_addr;
     CachedCodeMetadata *meta = NULL;
     PyObject *func = NULL;
     PyObject *file = NULL;
@@ -291,9 +292,9 @@ parse_code_object(RemoteUnwinderObject *unwinder,
 #ifdef Py_GIL_DISABLED
     // In free threading builds, code object addresses might have the low bit set
     // as a flag, so we need to mask it off to get the real address
-    uintptr_t real_address = address & (~1);
+    uintptr_t real_address = ctx->code_addr & (~1);
 #else
-    uintptr_t real_address = address;
+    uintptr_t real_address = ctx->code_addr;
 #endif
 
     if (unwinder && unwinder->code_object_cache != NULL) {
@@ -360,12 +361,12 @@ parse_code_object(RemoteUnwinderObject *unwinder,
         linetable = NULL;
     }
 
-    uintptr_t ip = instruction_pointer;
+    uintptr_t ip = ctx->instruction_pointer;
     ptrdiff_t addrq;
 
 #ifdef Py_GIL_DISABLED
     // Handle thread-local bytecode (TLBC) in free threading builds
-    if (tlbc_index == 0 || unwinder->debug_offsets.code_object.co_tlbc == 0 || unwinder == NULL) {
+    if (ctx->tlbc_index == 0 || unwinder->debug_offsets.code_object.co_tlbc == 0 || unwinder == NULL) {
         // No TLBC or no unwinder - use main bytecode directly
         addrq = (uint16_t *)ip - (uint16_t *)meta->addr_code_adaptive;
         goto done_tlbc;
@@ -383,10 +384,12 @@ parse_code_object(RemoteUnwinderObject *unwinder,
         tlbc_entry = get_tlbc_cache_entry(unwinder, real_address, unwinder->tlbc_generation);
     }
 
-    if (tlbc_entry && tlbc_index < tlbc_entry->tlbc_array_size) {
+    if (tlbc_entry && ctx->tlbc_index < tlbc_entry->tlbc_array_size) {
+        assert(ctx->tlbc_index >= 0);
+        assert(tlbc_entry->tlbc_array_size > 0);
         // Use cached TLBC data
         uintptr_t *entries = (uintptr_t *)((char *)tlbc_entry->tlbc_array + sizeof(Py_ssize_t));
-        uintptr_t tlbc_bytecode_addr = entries[tlbc_index];
+        uintptr_t tlbc_bytecode_addr = entries[ctx->tlbc_index];
 
         if (tlbc_bytecode_addr != 0) {
             // Calculate offset from TLBC bytecode
@@ -401,8 +404,6 @@ parse_code_object(RemoteUnwinderObject *unwinder,
 done_tlbc:
 #else
     // Non-free-threaded build, always use the main bytecode
-    (void)tlbc_index; // Suppress unused parameter warning
-    (void)unwinder;   // Suppress unused parameter warning
     addrq = (uint16_t *)ip - (uint16_t *)meta->addr_code_adaptive;
 #endif
     ;  // Empty statement to avoid C23 extension warning

@@ -44,7 +44,9 @@ frame_cache_find(RemoteUnwinderObject *unwinder, uint64_t thread_id)
         return NULL;
     }
     for (int i = 0; i < FRAME_CACHE_MAX_THREADS; i++) {
+        assert(i >= 0 && i < FRAME_CACHE_MAX_THREADS);
         if (unwinder->frame_cache[i].thread_id == thread_id) {
+            assert(unwinder->frame_cache[i].num_addrs <= FRAME_CACHE_MAX_FRAMES);
             return &unwinder->frame_cache[i];
         }
     }
@@ -154,6 +156,8 @@ frame_cache_lookup_and_extend(
         return 0;
     }
 
+    assert(entry->num_addrs >= 0 && entry->num_addrs <= FRAME_CACHE_MAX_FRAMES);
+
     // Find the index where last_profiled_frame matches
     Py_ssize_t start_idx = -1;
     for (Py_ssize_t i = 0; i < entry->num_addrs; i++) {
@@ -166,6 +170,7 @@ frame_cache_lookup_and_extend(
     if (start_idx < 0) {
         return 0;  // Not found
     }
+    assert(start_idx < entry->num_addrs);
 
     Py_ssize_t num_frames = PyList_GET_SIZE(entry->frame_list);
 
@@ -225,6 +230,7 @@ frame_cache_store(
     if (num_addrs > FRAME_CACHE_MAX_FRAMES) {
         num_addrs = FRAME_CACHE_MAX_FRAMES;
     }
+    assert(num_addrs >= 0 && num_addrs <= FRAME_CACHE_MAX_FRAMES);
 
     FrameCacheEntry *entry = frame_cache_alloc_slot(unwinder, thread_id);
     if (!entry) {
@@ -245,6 +251,8 @@ frame_cache_store(
     entry->thread_id = thread_id;
     memcpy(entry->addrs, addrs, num_addrs * sizeof(uintptr_t));
     entry->num_addrs = num_addrs;
+    assert(entry->num_addrs == num_addrs);
+    assert(entry->thread_id == thread_id);
 
     return 1;
 }