writeStackTrace now officially has no IO effect anymore for more convenient debugging

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.

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.

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: