From 6266c68ab6e4eaf247132dd867e055fa733675df Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Sun, 21 Jan 2018 21:08:51 +0100
Subject: [PATCH] writeStackTrace now officially has no IO effect anymore for
 more convenient debugging

---
 changelog.md         | 3 +++
 lib/system.nim       | 5 +++--
 lib/system/excpt.nim | 4 ++--
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/changelog.md b/changelog.md
index bce2bcca34..f7a656937c 100644
--- a/changelog.md
+++ b/changelog.md
@@ -220,3 +220,6 @@ styledEcho "Red on Green.", resetStyle
 - If you use ``--dynlibOverride:ssl`` with OpenSSL 1.0.x, you now have to
   define ``openssl10`` symbol (``-d:openssl10``). By default OpenSSL 1.1.x is
   assumed.
+
+- ``writeStackTrace`` is now proclaimed to have no IO effect (even though it does)
+  so that it is more useful for debugging purposes.
diff --git a/lib/system.nim b/lib/system.nim
index 8f83fb8c38..2c0617e4d5 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -3211,9 +3211,10 @@ when not defined(JS): #and not defined(nimscript):
       ## allows you to override the behaviour of your application when CTRL+C
       ## is pressed. Only one such hook is supported.
 
-    proc writeStackTrace*() {.tags: [WriteIOEffect], gcsafe.}
+    proc writeStackTrace*() {.tags: [], gcsafe.}
       ## writes the current stack trace to ``stderr``. This is only works
-      ## for debug builds.
+      ## for debug builds. Since it's usually used for debugging, this
+      ## is proclaimed to have no IO effect!
     when hostOS != "standalone":
       proc getStackTrace*(): string {.gcsafe.}
         ## gets the current stack trace. This only works for debug builds.
diff --git a/lib/system/excpt.nim b/lib/system/excpt.nim
index 8e42ea4683..0087c61395 100644
--- a/lib/system/excpt.nim
+++ b/lib/system/excpt.nim
@@ -386,9 +386,9 @@ proc writeStackTrace() =
   when hasSomeStackTrace:
     var s = ""
     rawWriteStackTrace(s)
-    showErrorMessage(s)
+    cast[proc (s: string) {.noSideEffect, tags: [], nimcall.}](showErrorMessage)(s)
   else:
-    showErrorMessage("No stack traceback available\n")
+    cast[proc (s: string) {.noSideEffect, tags: [], nimcall.}](showErrorMessage)("No stack traceback available\n")
 
 proc getStackTrace(): string =
   when hasSomeStackTrace: