diff mbox series

[4/7] manual: Clarify undefined behavior of feenableexcept (BZ 31019)

Message ID 20231103122416.2724355-5-adhemerval.zanella@linaro.org
State Superseded
Headers show
Series Multiple floating-point environment fixes | expand

Commit Message

Adhemerval Zanella Netto Nov. 3, 2023, 12:24 p.m. UTC
From: Bruno Haible <bruno@clisp.org>

* manual/arith.texi (Control Functions): Explain undefined behavior
of feenableexcept in a special case.
---
 manual/arith.texi | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Joseph Myers Nov. 3, 2023, 4:20 p.m. UTC | #1
On Fri, 3 Nov 2023, Adhemerval Zanella wrote:

> +Note: Enabling traps for an exception for which the exception flag is
> +currently already set (@pxref{Status bit operations}) has undefined
> +consequences: it may or may not trigger a trap immediately.

I think we should say "unspecified", not "undefined" (in the manual and 
commit message).  It might trap immediately, on a future floating-point 
instruction or not at all, but there shouldn't be any other possibilities; 
it's not undefined behavior.
Bruno Haible Nov. 6, 2023, 12:17 a.m. UTC | #2
Joseph Myers wrote:
> I think we should say "unspecified", not "undefined" (in the manual and 
> commit message).

I agree. Thanks Joseph for the more precise wording.

Bruno
Adhemerval Zanella Netto Nov. 6, 2023, 11:25 a.m. UTC | #3
On 05/11/23 21:17, Bruno Haible wrote:
> Joseph Myers wrote:
>> I think we should say "unspecified", not "undefined" (in the manual and 
>> commit message).
> 
> I agree. Thanks Joseph for the more precise wording.
> 
> Bruno

Ack.
diff mbox series

Patch

diff --git a/manual/arith.texi b/manual/arith.texi
index fa7110e992..68c6446a5b 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -1176,6 +1176,12 @@  enabled, the status of the other exceptions is not changed.
 
 The function returns the previous enabled exceptions in case the
 operation was successful, @code{-1} otherwise.
+
+Note: Enabling traps for an exception for which the exception flag is
+currently already set (@pxref{Status bit operations}) has undefined
+consequences: it may or may not trigger a trap immediately.
+@c It triggers a trap immediately on powerpc*, at the next floating-
+@c instruction on i386, and not at all on the other CPUs.
 @end deftypefun
 
 @deftypefun int fedisableexcept (int @var{excepts})