Crash reports keep the start of a long dump (the crashing thread) as well as its end

Author: Vic-Nas

launcher/Launch.cs

@@ -297,7 +297,11 @@ static string CrashLogSinceSent(string dir)
                 try { offset = long.Parse(File.ReadAllText(Path.Combine(dir, "lapsecoin-crash.sent")).Trim()); } catch (Exception) { }
                 if (offset < 0 || offset > text.Length) offset = 0;
                 string tail = text.Substring((int)offset);
-                return tail.Length > MaxTrace ? tail.Substring(tail.Length - MaxTrace) : tail;
+                if (tail.Length <= MaxTrace) return tail;
+                // A native crash dump starts with the thread that crashed, so keep the start too.
+                const string gap = "\n[...]\n";
+                int head = MaxTrace / 2;
+                return tail.Substring(0, head) + gap + tail.Substring(tail.Length - (MaxTrace - head - gap.Length));
             }
             catch (Exception) { return ""; }
         }

src/crashlog.py

@@ -210,6 +210,16 @@ def _start_log_tail(lines=15):
         return ""
 
 
+def _head_and_tail(text, limit):
+    """A native crash dump starts with the thread that crashed and a Python
+    traceback ends with the error, so a long text keeps both ends."""
+    if len(text) <= limit:
+        return text
+    gap = "\n[...]\n"
+    head = limit // 2
+    return text[:head] + gap + text[-(limit - head - len(gap)):]
+
+
 def build_payload(kind, where, trace, sig):
     """What is sent: nothing beyond this."""
     import platform
@@ -221,7 +231,7 @@ def build_payload(kind, where, trace, sig):
     return {"v": 1, "kind": kind, "where": where, "sig": sig,
             "app": version, "windows": platform.version(), "arch": platform.machine(),
             "python": platform.python_version(), "packaged": _packaged(),
-            "trace": sanitize(trace)[-MAX_TRACE:],
+            "trace": _head_and_tail(sanitize(trace), MAX_TRACE),
             "steps": sanitize(_start_log_tail())[-MAX_STEPS:]}
 
 

tests/test_crashlog.py

@@ -276,6 +276,14 @@ def test_a_log_with_nothing_critical_sends_nothing(self, reporting, monkeypatch)
             assert gh.requests == []
 
 
+class TestLongDumps:
+    def test_a_long_dump_keeps_the_crashing_thread_and_the_end(self):
+        dump = "Windows fatal exception: access violation\n" + "x" * 9000 + "\nTHE END"
+        kept = crashlog._head_and_tail(dump, crashlog.MAX_TRACE)
+        assert kept.startswith("Windows fatal exception") and kept.endswith("THE END")
+        assert len(kept) == crashlog.MAX_TRACE
+
+
 class TestWhatIsSent:
     def test_the_account_name_paths_and_addresses_are_taken_out(self, reporting, monkeypatch):
         monkeypatch.setenv("USERNAME", "Vic")