Add ccache stats during build time

Author: prigoyal

.jenkins/build.sh

@@ -1,5 +1,18 @@
 #!/bin/bash
 
+# NB: define this function before set -x, so that we don't
+# pollute the log with a premature EXITED_USER_LAND ;)
+function cleanup {
+  # Note that if you've exited user land, then CI will conclude that
+  # any failure is the CI's fault.  So we MUST only output this
+  # string
+  retcode=$?
+  set +x
+  if [ $retcode -eq 0 ]; then
+    echo "EXITED_USER_LAND"
+  fi
+}
+
 set -ex
 
 source /etc/lsb-release
@@ -8,6 +21,50 @@ source /etc/lsb-release
 # condition: if 16.04 and conda, conda install pytorch and build
 # condition: if any and non-conda, simply build TC from scratch
 
+# note: printf is used instead of echo to avoid backslash
+# processing and to properly handle values that begin with a '-'.
+echo "ENTERED_USER_LAND"
+log() { printf '%s\n' "$*"; }
+error() { log "ERROR: $*" >&2; }
+fatal() { error "$@"; exit 1; }
+
+# appends a command to a trap
+#
+# - 1st arg:  code to add
+# - remaining args:  names of traps to modify
+#
+trap_add() {
+    trap_add_cmd=$1; shift || fatal "${FUNCNAME} usage error"
+    for trap_add_name in "$@"; do
+        trap -- "$(
+            # helper fn to get existing trap command from output
+            # of trap -p
+            extract_trap_cmd() { printf '%s\n' "$3"; }
+            # print existing trap command with newline
+            eval "extract_trap_cmd $(trap -p "${trap_add_name}")"
+            # print the new trap command
+            printf '%s\n' "${trap_add_cmd}"
+        )" "${trap_add_name}" \
+            || fatal "unable to add to trap ${trap_add_name}"
+    done
+}
+# set the trace attribute for the above function.  this is
+# required to modify DEBUG or RETURN traps because functions don't
+# inherit them unless the trace attribute is set
+declare -f -t trap_add
+
+trap_add cleanup EXIT
+
+if which ccache > /dev/null; then
+  # Report ccache stats for easier debugging
+  ccache --zero-stats
+  ccache --show-stats
+  function ccache_epilogue() {
+    ccache --show-stats
+  }
+  trap_add ccache_epilogue EXIT
+fi
+
 if [[ "$DISTRIB_RELEASE" == 14.04 ]]; then
   if [[ $(conda --version | wc -c) -ne 0 ]]; then
     echo "Building TC in conda env"