refactor(appsec): move _stacktrace from _iast to _shared package

Move the native _stacktrace C extension from ddtrace/appsec/_iast/ to
ddtrace/appsec/_shared/ so it can be reused by both IAST and SCA
without creating a dependency from SCA into IAST internals.

Split out from #17156 to keep PRs incremental and reviewable.

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

Author: avara1986

ddtrace/appsec/_iast/_stacktrace.pyi

@@ -8,6 +8,7 @@
 from ddtrace.appsec._iast._taint_tracking import get_ranges
 from ddtrace.appsec._iast.sampling.vulnerability_detection import rollback_quota
 from ddtrace.appsec._iast.sampling.vulnerability_detection import should_process_vulnerability
+from ddtrace.appsec._shared._stacktrace import get_info_frame
 from ddtrace.appsec._trace_utils import _asm_manual_keep
 from ddtrace.internal import core
 from ddtrace.internal.logger import get_logger
@@ -19,7 +20,6 @@
 from .._iast_request_context import get_iast_reporter
 from .._iast_request_context import set_iast_reporter
 from .._span_metrics import increment_iast_span_metric
-from .._stacktrace import get_info_frame
 from ..reporter import Evidence
 from ..reporter import IastSpanReporter
 from ..reporter import Location

ddtrace/appsec/_iast/taint_sinks/_base.py

@@ -359,7 +359,7 @@ static PyMethodDef StacktraceMethods[] = { { "get_info_frame",
                                            { NULL, NULL, 0, NULL } };
 
 static struct PyModuleDef stacktrace = { PyModuleDef_HEAD_INIT,
-                                         "ddtrace.appsec._iast._stacktrace",
+                                         "ddtrace.appsec._shared._stacktrace",
                                          "stacktrace module",
                                          -1,
                                          StacktraceMethods };

ddtrace/appsec/_shared/__init__.py

@@ -0,0 +1,3 @@
+from typing import Optional
+
+def get_info_frame() -> tuple[Optional[str], Optional[int], Optional[str], Optional[str]]: ...

ddtrace/appsec/_iast/_stacktrace.c ddtrace/appsec/_shared/_stacktrace.cddtrace/appsec/_iast/_stacktrace.c renamed to ddtrace/appsec/_shared/_stacktrace.c

@@ -1275,9 +1275,9 @@ def get_exts_for(name):
     if platform.system() not in ("Windows", ""):
         ext_modules.append(
             Extension(
-                "ddtrace.appsec._iast._stacktrace",
+                "ddtrace.appsec._shared._stacktrace",
                 sources=[
-                    "ddtrace/appsec/_iast/_stacktrace.c",
+                    "ddtrace/appsec/_shared/_stacktrace.c",
                 ],
                 extra_compile_args=extra_compile_args + debug_compile_args + fast_build_args,
             )

ddtrace/appsec/_shared/_stacktrace.pyi

@@ -17,7 +17,7 @@
 MODULE_IAST_ONLY = [
     "ddtrace.appsec._iast",
     "ddtrace.appsec._iast._taint_tracking._native",
-    "ddtrace.appsec._iast._stacktrace",
+    "ddtrace.appsec._shared._stacktrace",
 ]
 
 

setup.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-from ddtrace.appsec._iast._stacktrace import get_info_frame
+from ddtrace.appsec._shared._stacktrace import get_info_frame
 
 
 def test_stacktrace():

tests/appsec/architectures/test_appsec_loading_modules.py

@@ -1,6 +1,6 @@
 import os
 
-from ddtrace.appsec._iast._stacktrace import get_info_frame
+from ddtrace.appsec._shared._stacktrace import get_info_frame
 
 
 CWD = os.path.abspath(os.getcwd())

tests/appsec/iast/test_stacktrace.py

@@ -8,11 +8,11 @@
 from ddtrace.appsec._iast._iast_request_context_base import _iast_finish_request
 from ddtrace.appsec._iast._iast_request_context_base import _iast_start_request
 from ddtrace.appsec._iast._iast_request_context_base import _num_objects_tainted_in_request
-from ddtrace.appsec._iast._stacktrace import get_info_frame
 from ddtrace.appsec._iast._taint_tracking import OriginType
 from ddtrace.appsec._iast._taint_tracking._context import debug_context_array_size
 from ddtrace.appsec._iast._taint_tracking._taint_objects import taint_pyobject
 from ddtrace.appsec._iast._taint_tracking._taint_objects_base import get_tainted_ranges
+from ddtrace.appsec._shared._stacktrace import get_info_frame
 from tests.appsec.iast.iast_utils import _iast_patched_module
 from tests.appsec.iast_memcheck.fixtures.stacktrace import func_1