Don't truncate traceEvents to 512 bytes (#8309)

Summary:
Don't call postLogMsg to post a user msg, because it truncates messages to
512 bytes.

Rename traceCap_stderr and trace_stderr to vtraceCap_stderr and trace_stderr,
to signal that they take a va_list (similar to vdebugBelch vs debugBelch).

See #3874 for the original reason behind traceFormatUserMsg.

See the commit msg in #9395 (d360d440) for a discussion about using
null-terminated strings vs strings with an explicit length.

Test Plan:
Run `cabal install ghc-events` and inspect the result of `ghc-events show` on
an eventlog file created with `ghc -eventlog Test.hs` and `./Test +RTS -l`,
where Test.hs contains:

```
import Debug.Trace
main = traceEvent (replicate 510 'a' ++ "bcd") $ return ()
```

Depends on D655.

Reviewers: austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D656

GHC Trac Issues: #8309

2 files changed, 5 insertions, 12 deletions

diff --git a/rts/eventlog/EventLog.c b/rts/eventlog/EventLog.c
index f830ec19a0..5f021a68b6 100644
--- a/rts/eventlog/EventLog.c
+++ b/rts/eventlog/EventLog.c
@@ -1078,11 +1078,6 @@ void postCapMsg(Capability *cap, char *msg, va_list ap)
     postLogMsg(&capEventBuf[cap->no], EVENT_LOG_MSG, msg, ap);
 }
 
-void postUserMsg(Capability *cap, char *msg, va_list ap)
-{
-    postLogMsg(&capEventBuf[cap->no], EVENT_USER_MSG, msg, ap);
-}
-
 void postEventStartup(EventCapNo n_caps)
 {
     ACQUIRE_LOCK(&eventBufMutex);
@@ -1099,10 +1094,10 @@ void postEventStartup(EventCapNo n_caps)
     RELEASE_LOCK(&eventBufMutex);
 }
 
-void postUserMarker(Capability *cap, char *markername)
+void postUserEvent(Capability *cap, EventTypeNum type, char *msg)
 {
     EventsBuf *eb;
-    int size = strlen(markername);
+    int size = strlen(msg);
 
     eb = &capEventBuf[cap->no];
 
@@ -1115,9 +1110,9 @@ void postUserMarker(Capability *cap, char *markername)
         }
     }
 
-    postEventHeader(eb, EVENT_USER_MARKER);
+    postEventHeader(eb, type);
     postPayloadSize(eb, size);
-    postBuf(eb, (StgWord8*) markername, size);
+    postBuf(eb, (StgWord8*) msg, size);
 }
 
 void postThreadLabel(Capability    *cap,
diff --git a/rts/eventlog/EventLog.h b/rts/eventlog/EventLog.h
index 85370e9843..9c2f265970 100644
--- a/rts/eventlog/EventLog.h
+++ b/rts/eventlog/EventLog.h
@@ -45,12 +45,10 @@ void postEventAtTimestamp (Capability *cap, EventTimestamp ts,
 
 void postMsg(char *msg, va_list ap);
 
-void postUserMsg(Capability *cap, char *msg, va_list ap);
+void postUserEvent(Capability *cap, EventTypeNum type, char *msg);
 
 void postCapMsg(Capability *cap, char *msg, va_list ap);
 
-void postUserMarker(Capability *cap, char *markername);
-
 void postEventStartup(EventCapNo n_caps);
 
 /*