linux-kernel - Re: minor bug in invalid exception patch

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Date:	Wed, 22 Oct 2008 22:10:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	galak@...nel.crashing.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: minor bug in invalid exception patch

From: David Miller <davem@...emloft.net>
Date: Tue, 21 Oct 2008 23:24:21 -0700 (PDT)

> Specifically:
> 
> @@ -490,11 +490,15 @@ do {							\
>      break;						\
>  							\
>    case _FP_CLS_COMBINE(FP_CLS_INF,FP_CLS_INF):		\
> +    R##_s = _FP_NANSIGN_##fs;				\
> +    R##_c = FP_CLS_NAN;					\
> +    _FP_FRAC_SET_##wc(R, _FP_NANFRAC_##fs);		\
> +    FP_SET_EXCEPTION(FP_EX_INVALID | FP_EX_INVALID_IDI);\
>    case _FP_CLS_COMBINE(FP_CLS_ZERO,FP_CLS_ZERO):	\
>      R##_s = _FP_NANSIGN_##fs;				\
>      R##_c = FP_CLS_NAN;					\
>      _FP_FRAC_SET_##wc(R, _FP_NANFRAC_##fs);		\
> -    FP_SET_EXCEPTION(FP_EX_INVALID);			\
> +    FP_SET_EXCEPTION(FP_EX_INVALID | FP_EX_INVALID_ZDZ);\
>      break;						\
>  							\
>    default:						\
> 
> That first case statement code block falls through to
> the next one, which is probably not as you intended.
> 
> Seems there is a missing break there.

I'm going to commit the following to fix this:

--------------------

math-emu: Fix thinko in _FP_DIV

In commit 48d6c64311ddb6417b901639530ccbc47bdc7635 ("math-emu: Add
support for reporting exact invalid exception") code was added to
set the new FP_EX_INVALID_{IDI,ZDZ} exception flag bits.

However there is a missing break statement for the
_FP_CLS_COMBINE(FP_CLS_INF,FP_CLS_INF) switch case, the
code just falls into _FP_CLS_COMBINE(FP_CLS_ZERO,FP_CLS_ZERO)
which then proceeds to overwrite all of the settings.

Fix by adding the missing break.

Signed-off-by: David S. Miller <davem@...emloft.net>
---
 include/math-emu/op-common.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/math-emu/op-common.h b/include/math-emu/op-common.h
index bc50aa0..f456534 100644
--- a/include/math-emu/op-common.h
+++ b/include/math-emu/op-common.h
@@ -503,6 +503,8 @@ do {							\
     R##_c = FP_CLS_NAN;					\
     _FP_FRAC_SET_##wc(R, _FP_NANFRAC_##fs);		\
     FP_SET_EXCEPTION(FP_EX_INVALID | FP_EX_INVALID_IDI);\
+    break;						\
+							\
   case _FP_CLS_COMBINE(FP_CLS_ZERO,FP_CLS_ZERO):	\
     R##_s = _FP_NANSIGN_##fs;				\
     R##_c = FP_CLS_NAN;					\
-- 
1.5.6.5

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