--exception:goto switch for deterministic exception handling (#12977)

This implements "deterministic" exception handling for Nim based on goto instead of setjmp. This means raising an exception is much cheaper than in C++'s table based implementations. Supports hard realtime systems. Default for --gc:arc and the C target because it's generally a good idea and arc is all about deterministic behavior.

Note: This implies that fatal runtime traps are not catchable anymore! This needs to be documented.

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/system.nim b/lib/system.nim
index 58250db3f..838205c57 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -3105,7 +3105,7 @@ when not defined(js):
   when defined(nimV2):
     type
       TNimNode {.compilerproc.} = object # to keep the code generator simple
-      DestructorProc = proc (p: pointer) {.nimcall, benign.}
+      DestructorProc = proc (p: pointer) {.nimcall, benign, raises: [].}
       TNimType {.compilerproc.} = object
         destructor: pointer
         size: int
@@ -3120,6 +3120,12 @@ when not defined(js):
 
   {.pop.}
 
+when not defined(js) and not defined(nimscript):
+  proc writeStackTrace*() {.tags: [], gcsafe, raises: [].}
+    ## Writes the current stack trace to ``stderr``. This is only works
+    ## for debug builds. Since it's usually used for debugging, this
+    ## is proclaimed to have no IO effect!
+
 when not declared(sysFatal):
   include "system/fatal"
 
@@ -3693,10 +3699,6 @@ when not defined(JS): #and not defined(nimscript):
       proc unsetControlCHook*()
         ## Reverts a call to setControlCHook.
 
-    proc writeStackTrace*() {.tags: [], gcsafe.}
-      ## Writes the current stack trace to ``stderr``. This is only works
-      ## 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.