From: Taylor R Campbell <campbell@mumble.net>
Date: Mon, 26 Aug 2019 03:14:22 +0000 (+0000)
Subject: If enabling fp traps for first time, clear sticky exceptions.
X-Git-Tag: mit-scheme-pucked-10.1.20~11^2~58
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=5e3de39d43d7b9736a5583073112e237a5da00a9;p=mit-scheme.git

If enabling fp traps for first time, clear sticky exceptions.

Otherwise, the indeterminate state of the sticky exceptions --
possibly from another thread -- may cause the machine to trap merely
by enabling traps.

Also, don't bother marking the floating-point environment in use when
disabling traps.
---

diff --git a/src/runtime/floenv.scm b/src/runtime/floenv.scm
index fc6254859..149e815da 100644
--- a/src/runtime/floenv.scm
+++ b/src/runtime/floenv.scm
@@ -245,15 +245,20 @@ USA.
   ((ucode-primitive restore-float-exception-flags 2) fexcept exceptions))
 
 (define (flo:set-trapped-exceptions! exceptions)
-  (use-floating-point-environment!)
+  (if (not (using-floating-point-environment?))
+      (begin
+	((ucode-primitive clear-float-exceptions 1) exceptions)
+	(use-floating-point-environment!)))
   ((ucode-primitive set-trapped-float-exceptions 1) exceptions))
 
 (define (flo:trap-exceptions! exceptions)
-  (use-floating-point-environment!)
+  (if (not (using-floating-point-environment?))
+      (begin
+	((ucode-primitive clear-float-exceptions 1) exceptions)
+	(use-floating-point-environment!)))
   ((ucode-primitive trap-float-exceptions 1) exceptions))
 
 (define (flo:untrap-exceptions! exceptions)
-  (use-floating-point-environment!)
   ((ucode-primitive untrap-float-exceptions 1) exceptions))
 
 (define (flo:defer-exception-traps!)