From 4af215362bdf2d9a4dfe68c3a2834b8f77007bd4 Mon Sep 17 00:00:00 2001
From: J-P Nurmi <jpnurmi@gmail.com>
Date: Wed, 3 Jun 2026 11:39:58 +0200
Subject: [PATCH 1/2] test: trigger crashes with correct WER exception codes
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For stack-buffer-overruns, the example uses `RaiseFailFastException` as
appropriate, but for fastfails, it used `__fastfail(77)` that made WER
deliver `STATUS_STACK_BUFFER_OVERRUN (0xC0000409)`.

- `__fastfail(77)` → `kernel int 0x29` → WER always normalizes to
  `STATUS_STACK_BUFFER_OVERRUN (0xC0000409)`
  https://learn.microsoft.com/en-us/cpp/intrinsics/fastfail

vs.

- `RaiseFailFastException(NULL, NULL, 0)` → WER preserves the original
  exception code `(STATUS_FAIL_FAST_EXCEPTION = 0xC0000602)`
  https://learn.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-raisefailfastexception
---
 examples/example.c               |  6 +++---
 src/backends/native/sentry_wer.c |  8 ++++++++
 tests/test_integration_native.py | 12 +++++++++---
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/examples/example.c b/examples/example.c
index d3a083280..25200de27 100644
--- a/examples/example.c
+++ b/examples/example.c
@@ -416,9 +416,9 @@ trigger_stack_buffer_overrun()
 static void
 trigger_fastfail_crash()
 {
-    // this bypasses WINDOWS SEH and will only be caught with the crashpad WER
-    // module enabled
-    __fastfail(77);
+    // this bypasses WINDOWS SEH and will only be caught with the
+    // crashpad/native WER module enabled
+    RaiseFailFastException(NULL, NULL, 0);
 }
 
 #endif
diff --git a/src/backends/native/sentry_wer.c b/src/backends/native/sentry_wer.c
index 37542528c..3657543a4 100644
--- a/src/backends/native/sentry_wer.c
+++ b/src/backends/native/sentry_wer.c
@@ -146,6 +146,14 @@ process_wer_exception(
         ctx->platform.threads[0].thread_id = ctx->crashed_tid;
         ctx->platform.threads[0].context = exception_info->context;
 
+        char buf[4096];
+        snprintf(buf, sizeof(buf),
+            "### SENTRY_WER: crashed_pid=%lu crashed_tid=%llu "
+            "exception_code=0x%08X",
+            (unsigned long)ctx->crashed_pid,
+            (unsigned long long)ctx->crashed_tid, ctx->platform.exception_code);
+        OutputDebugStringA(buf);
+
         InterlockedExchange(&ctx->state, SENTRY_CRASH_STATE_CRASHED);
         if (SetEvent(event)) {
             claimed = TRUE;
diff --git a/tests/test_integration_native.py b/tests/test_integration_native.py
index 3132aa4f5..54180014b 100644
--- a/tests/test_integration_native.py
+++ b/tests/test_integration_native.py
@@ -88,8 +88,14 @@ def test_native_capture_crash(cmake, httpserver):
     reason="WER crash tests are only available in MSVC Windows builds",
 )
 @pytest.mark.with_wer
-@pytest.mark.parametrize("crash_arg", ["fastfail", "stack-buffer-overrun"])
-def test_native_wer(cmake, httpserver, crash_arg):
+@pytest.mark.parametrize(
+    "crash_arg,exception_code",
+    [
+        pytest.param("fastfail", 0xC0000602, id="fastfail"),
+        pytest.param("stack-buffer-overrun", 0xC0000409, id="stack-buffer-overrun"),
+    ],
+)
+def test_native_wer_crash(cmake, httpserver, crash_arg, exception_code):
     """Test WER crash capture with native backend"""
     tmp_path = cmake(["sentry_example"], {"SENTRY_BACKEND": "native"})
 
@@ -106,7 +112,7 @@ def test_native_wer(cmake, httpserver, crash_arg):
 
     assert len(httpserver.log) >= 1
     envelope = Envelope.deserialize(httpserver.log[0][0].get_data())
-    assert_native_crash(envelope, exception_code=0xC0000409)
+    assert_native_crash(envelope, exception_code=exception_code)
 
 
 @pytest.mark.skipif(not has_oom, reason="OOM test unreliable in this environment")

From af1795f9b9cc3cefcecb613dc6575ce60619a668 Mon Sep 17 00:00:00 2001
From: J-P Nurmi <jpnurmi@gmail.com>
Date: Wed, 3 Jun 2026 12:06:59 +0200
Subject: [PATCH 2/2] clean up debug output

---
 src/backends/native/sentry_wer.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/src/backends/native/sentry_wer.c b/src/backends/native/sentry_wer.c
index 3657543a4..37542528c 100644
--- a/src/backends/native/sentry_wer.c
+++ b/src/backends/native/sentry_wer.c
@@ -146,14 +146,6 @@ process_wer_exception(
         ctx->platform.threads[0].thread_id = ctx->crashed_tid;
         ctx->platform.threads[0].context = exception_info->context;
 
-        char buf[4096];
-        snprintf(buf, sizeof(buf),
-            "### SENTRY_WER: crashed_pid=%lu crashed_tid=%llu "
-            "exception_code=0x%08X",
-            (unsigned long)ctx->crashed_pid,
-            (unsigned long long)ctx->crashed_tid, ctx->platform.exception_code);
-        OutputDebugStringA(buf);
-
         InterlockedExchange(&ctx->state, SENTRY_CRASH_STATE_CRASHED);
         if (SetEvent(event)) {
             claimed = TRUE;