From 287edce0090a14fdd88a9e10d13327e74e52831a Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Thu, 5 Jan 2017 20:43:49 +0100
Subject: erts: Fix GC tracing to use temp heap

Can't use HAlloc as it might consume part of callers 'need'.
---
 erts/emulator/beam/erl_gc.c    | 3 ++-
 erts/emulator/beam/erl_nif.c   | 4 ++--
 erts/emulator/beam/erl_trace.c | 5 ++++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index 50f09277fa..b05209402d 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -602,7 +602,7 @@ garbage_collect(Process* p, ErlHeapFragment *live_hf_end,
     Uint reclaimed_now = 0;
     Eterm gc_trace_end_tag;
     int reds;
-    ErtsMonotonicTime start_time = 0; /* Shut up faulty warning... */
+    ErtsMonotonicTime start_time;
     ErtsSchedulerData *esdp;
     erts_aint32_t state;
     ERTS_MSACC_PUSH_STATE_M();
@@ -610,6 +610,7 @@ garbage_collect(Process* p, ErlHeapFragment *live_hf_end,
     DTRACE_CHARBUF(pidbuf, DTRACE_TERM_BUF_SIZE);
 #endif
 
+    ERTS_UNDEF(start_time, 0);
     ERTS_CHK_MBUF_SZ(p);
 
     ASSERT(CONTEXT_REDS - ERTS_REDS_LEFT(p, fcalls)
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 6b265a8b80..19ce0f6965 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -3561,8 +3561,8 @@ Eterm erts_nif_call_function(Process *p, Process *tracee,
 #endif
     if (p) {
         /* This is almost a normal nif call like in beam_emu,
-           except that any heap fragment created in the nif will be
-           discarded without checking if anything in it is live.
+           except that any heap consumed by the nif will be
+           released without checking if anything in it is live.
            This is because we cannot do a GC here as we don't know
            the number of live registers that have to be preserved.
            This means that any heap part of the returned term may
diff --git a/erts/emulator/beam/erl_trace.c b/erts/emulator/beam/erl_trace.c
index 8c84303997..ac9e91e31f 100644
--- a/erts/emulator/beam/erl_trace.c
+++ b/erts/emulator/beam/erl_trace.c
@@ -1436,6 +1436,7 @@ void
 trace_gc(Process *p, Eterm what, Uint size, Eterm msg)
 {
     ErtsTracerNif *tnif = NULL;
+    Eterm* o_hp = NULL;
     Eterm* hp;
     Uint sz = 0;
     Eterm tup;
@@ -1446,7 +1447,7 @@ trace_gc(Process *p, Eterm what, Uint size, Eterm msg)
         if (is_non_value(msg)) {
 
             (void) erts_process_gc_info(p, &sz, NULL, 0, 0);
-            hp = HAlloc(p, sz + 3 + 2);
+            o_hp = hp = erts_alloc(ERTS_ALC_T_TMP, (sz + 3 + 2) * sizeof(Eterm));
 
             msg = erts_process_gc_info(p, NULL, &hp, 0, 0);
             tup = TUPLE2(hp, am_wordsize, make_small(size)); hp += 3;
@@ -1455,6 +1456,8 @@ trace_gc(Process *p, Eterm what, Uint size, Eterm msg)
 
         send_to_tracer_nif(p, &p->common, p->common.id, tnif, TRACE_FUN_T_GC,
                            what, msg, THE_NON_VALUE, am_true);
+        if (o_hp)
+            erts_free(ERTS_ALC_T_TMP, o_hp);
     }
 }
 
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