From: Peter Stephenson <p.stephenson@samsung.com>
To: zsh-workers@zsh.org
Subject: Re: Undefined behaviour warnings with zsh.git and clang
Date: Tue, 14 Jul 2015 10:20:33 +0100 [thread overview]
Message-ID: <20150714102033.0f92c5de@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <loom.20150714T104717-624@post.gmane.org>
On Tue, 14 Jul 2015 08:48:17 +0000
İsmailDönmez <ismail@donmez.ws> wrote:
> With git master I started to see:
>
> clang -c -I. -I../Src -I../Src -I../Src/Zle -I. -DHAVE_CONFIG_H -O2 -fPIE -
> fstack-protector -I/usr/include/ncurses6/ncursesw -I/usr/include/ncurses6 -
> o params.o params.c
> params.c:1721:18: warning: shifting a negative signed value is undefined [-
> Wshift-negative-value]
> v->isarr |= SCANPM_ISVAR_AT;
> ^~~~~~~~~~~~~~~
> ./zsh.h:1755:32: note: expanded from macro 'SCANPM_ISVAR_AT'
> #define SCANPM_ISVAR_AT ((-1)<<15) /* "$foo[@]"-style substitution
> ~~~~^
> params.c:1933:36: warning: shifting a negative signed value is undefined [-
> Wshift-negative-value]
This hasn't changed, but wherever the warning's started coming from it's
valid. I think the following uses the same bit patterns and final value
without any undefined behaviour, unless anyone can see otherwise.
Alaternatively (-1 & ~0xFFFF) might be neater.
pws
diff --git a/Src/zsh.h b/Src/zsh.h
index 69fef33..a99c900 100644
--- a/Src/zsh.h
+++ b/Src/zsh.h
@@ -1752,9 +1752,10 @@ struct tieddata {
* necessarily want to match multiple
* elements
*/
-#define SCANPM_ISVAR_AT ((-1)<<15) /* "$foo[@]"-style substitution
- * Only sign bit is significant
- */
+/* "$foo[@]"-style substitution
+ * Only sign bit is significant
+ */
+#define SCANPM_ISVAR_AT ((int)(((unsigned int)-1)<<15))
/*
* Flags for doing matches inside parameter substitutions, i.e.
prev parent reply other threads:[~2015-07-14 9:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-14 8:48 İsmailDönmez
2015-07-14 9:20 ` Peter Stephenson [this message]
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