sigtrace: use smarttraceback and print to stderr

Summary:
Make sigtrace use smarttraceback so it prints more context.
As we're here, also make it print to stderr so we don't need to find the
traceback from /tmp.

Reviewed By: xavierd

Differential Revision: D17066277

fbshipit-source-id: 9a1000803fed27a71ec381b8ddbd76400dae99c9

edenscm/hgext/sigtrace.py

@@ -25,7 +25,7 @@ import sys
 import time
 import traceback
 
-from edenscm.mercurial import registrar
+from edenscm.mercurial import registrar, util
 
 
 pathformat = "/tmp/trace-%(pid)s-%(time)s.log"
@@ -43,11 +43,17 @@ configitem("sigtrace", "memsignal", default="USR2")
 def printstacks(sig, currentframe):
     content = ""
     for tid, frame in sys._current_frames().iteritems():
-        content += "Thread %s:\n%s\n" % (tid, "".join(traceback.format_stack(frame)))
+        content += "Thread %s:\n%s\n" % (tid, util.smarttraceback(frame))
 
-    with open(pathformat % {"time": time.time(), "pid": os.getpid()}, "w") as f:
+    path = pathformat % {"time": time.time(), "pid": os.getpid()}
+    with open(path, "w") as f:
         f.write(content)
 
+    # Also print to stderr
+    sys.stderr.write(content)
+    sys.stderr.write("\nStacktrace written to %s\n" % path)
+    sys.stderr.flush()
+
 
 memorytracker = []
 

edenscm/mercurial/util.py

@@ -4553,7 +4553,7 @@ def describe(describefunc, _describecall=bindings.stackdesc.describecall):
 renderstack = bindings.stackdesc.renderstack
 
 
-def smarttraceback():
+def smarttraceback(frame=None):
     """Get a friendly traceback as a string.
 
     Based on some methods in the traceback.format_stack.
@@ -4563,10 +4563,11 @@ def smarttraceback():
     import linecache
 
     # Get the frame. See traceback.format_stack
-    try:
-        raise ZeroDivisionError
-    except ZeroDivisionError:
-        frame = sys.exc_info()[2].tb_frame.f_back
+    if frame is None:
+        try:
+            raise ZeroDivisionError
+        except ZeroDivisionError:
+            frame = sys.exc_info()[2].tb_frame.f_back
 
     # Similar to traceback.extract_stack
     frameinfos = []

tests/test-fb-hgext-sigtrace.t

@@ -19,7 +19,8 @@
 
 Test the default SIGUSR1 signal
 
-  $ hg signal USR1
+  $ hg signal USR1 2>&1 | tail -1
+  Stacktrace written to $TESTTMP/dump-*.log (glob)
   $ ls $TESTTMP/dump-*.log
   $TESTTMP/dump-*-*.log (glob)
   $ grep Thread $TESTTMP/dump-*.log | head -n 1
@@ -30,7 +31,8 @@ Test the signal config option
 
   $ echo 'signal=USR2' >> $HGRCPATH
   $ echo 'memsignal=USR1' >> $HGRCPATH
-  $ hg signal USR2
+  $ hg signal USR2  2>&1 | tail -1
+  Stacktrace written to $TESTTMP/dump-*.log (glob)
   $ ls $TESTTMP/dump-*.log
   $TESTTMP/dump-*-*.log (glob)
   $ grep Thread $TESTTMP/dump-*.log | head -n 1