From 05703fc86f81b5db050d70746af19183394cf326 Mon Sep 17 00:00:00 2001
From: mratsim <mamy_github@numforge.co>
Date: Fri, 15 Jun 2018 14:20:42 +0200
Subject: [PATCH] logging: non-debug costless, avoid allocating constant string
 messages

---
 nimbus/logging.nim       | 29 ++++++++++++++++++-----------
 tests/test_gas_meter.nim |  2 +-
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/nimbus/logging.nim b/nimbus/logging.nim
index 8caf9c04e..46d205be4 100644
--- a/nimbus/logging.nim
+++ b/nimbus/logging.nim
@@ -7,29 +7,36 @@
 
 import strformat, terminal
 
+# TODO replace by nim-chronicles
+
 type
   Logger* = object
     name*: string
 
-var DEBUG* = defined(nimbusdebug)
+const DEBUG* = defined(nimbusdebug)
 
-proc log*(l: Logger, msg: string, color: ForegroundColor = fgBlack) =
-  if DEBUG:
+# Note: to make logging costless:
+#  - DEBUG should be a const and dispatch should use `when` for compile-time specialization
+#  - Passing a string to a proc, even a const string and inline proc, might trigger a heap allocation
+#    use a template instead.
+
+template log*(l: Logger, msg: string, color: ForegroundColor = fgBlack) =
+  when DEBUG:
     styledWriteLine(stdout, color, &"#{l.name}: {msg}", resetStyle)
 
-proc debug*(l: Logger, msg: string) =
-  if DEBUG:
+template debug*(l: Logger, msg: string) =
+  when DEBUG:
     l.log(msg)
 
-proc trace*(l: Logger, msg: string) =
-  if DEBUG:
+template trace*(l: Logger, msg: string) =
+  when DEBUG:
     l.log(msg, fgBlue)
 
 proc getLogger*(name: string): Logger =
   result = Logger(name: name)
 
-proc disableLogging* =
-  DEBUG = false
+# proc disableLogging* =
+#   DEBUG = false
 
-proc enableLogging* =
-  DEBUG = true
+# proc enableLogging* =
+#   DEBUG = true
diff --git a/tests/test_gas_meter.nim b/tests/test_gas_meter.nim
index 9ad8e7aa5..542b2bb47 100644
--- a/tests/test_gas_meter.nim
+++ b/tests/test_gas_meter.nim
@@ -12,7 +12,7 @@ import  unittest, macros, strformat,
 # TODO: quicktest
 # PS: parametrize can be easily immitated, but still quicktests would be even more useful
 
-disableLogging()
+# disableLogging()
 
 proc gasMeters: seq[GasMeter] =
   @[newGasMeter(10), newGasMeter(100), newGasMeter(999)]