add simple backtrace support

src/base/backtrace.nim

@@ -0,0 +1,32 @@
+include system/ansi_c
+
+{. pragma: execinfo, header:"execinfo.h" .}
+
+proc backtrace(buffer: ptr pointer, size: cint): cint {.importc,execinfo.}
+proc backtrace_symbols(buffer: ptr pointer, size: cint): ptr UncheckedArray[cstring]
+    {.importc,execinfo.}
+
+proc print_trace =
+  #void *array[10];
+  const nmax = 10
+  var arr: array[nmax, pointer]
+  #char **strings;
+
+  let size = backtrace(addr arr[0], nmax)
+  let strings = backtrace_symbols(addr arr[0], size);
+  if not isNil strings:
+    echo "Stack trace of size: ", size
+    for i in 0..<size:
+      echo strings[i]
+  cfree strings
+
+proc sigtrace(sig: cint) {.noconv.} =
+  print_trace()
+
+proc setTrace* =
+  c_signal(SIGSEGV, sigtrace)
+
+when isMainModule:
+  print_trace()
+  setTrace()
+  discard c_raise(SIGSEGV)