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* -Wrestrict warning on cc 8.3.0
@ 2019-04-03 18:59 ` Wesley Schwengle
  2019-04-04 10:21   ` Peter Stephenson
  0 siblings, 1 reply; 4+ messages in thread
From: Wesley Schwengle @ 2019-04-03 18:59 UTC (permalink / raw)
  To: zsh-workers

Hello all,

During a make of the latest master I got the following warning:

gcc -c -I. -I../../Src -I../../Src -I../../Src/Zle -I.  -DHAVE_CONFIG_H
-DMODULE -Wall -Wmissing-prototypes -O2 -fPIC -o compctl..o compctl.c
compctl.c: In function ‘makecomplistflags.isra.6’:
compctl.c:3340:7: warning: ‘strcpy’ accessing 1 byte at offsets [0,
9223372036854775807] and [0,9223372036854775807] may overlap 1 byte at
offset 0 [-Wrestrict]
strcpy(p, p + bl);
^~~~~~~~~~~~~~~~~
rm -f compctl.so

Cheers,
Wesley

-- 
Wesley Schwengle, Developer
Mintlab B.V., https://www.zaaksysteem.nl
E: wesley@mintlab.nl
T:  +31 20 737 00 05

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: -Wrestrict warning on cc 8.3.0
  2019-04-03 18:59 ` -Wrestrict warning on cc 8.3.0 Wesley Schwengle
@ 2019-04-04 10:21   ` Peter Stephenson
  2019-04-10  8:48     ` Peter Stephenson
  0 siblings, 1 reply; 4+ messages in thread
From: Peter Stephenson @ 2019-04-04 10:21 UTC (permalink / raw)
  To: zsh-workers

On Wed, 2019-04-03 at 20:59 +0200, Wesley Schwengle wrote:
> During a make of the latest master I got the following warning:
> 
> gcc -c -I. -I../../Src -I../../Src -I../../Src/Zle -I.  -DHAVE_CONFIG_H
> -DMODULE -Wall -Wmissing-prototypes -O2 -fPIC -o compctl..o compctl.c
> compctl.c: In function ‘makecomplistflags.isra.6’:
> compctl.c:3340:7: warning: ‘strcpy’ accessing 1 byte at offsets [0,
> 9223372036854775807] and [0,9223372036854775807] may overlap 1 byte at
> offset 0 [-Wrestrict]
> strcpy(p, p + bl);
> ^~~~~~~~~~~~~~~~~
> rm -f compctl.so

This warning is thoroughly opaque --- and not occurring with a locally
compiled gcc 8.3.0 on my Ubuntu 16.04 64-bit Intel system --- but the
code isn't exactly crystal clear, either (subtracting a number off then
adding it immediately back on again isn't generally regarded as great
style), and it's quite possible the copy is overlapping.  Also, the last
person to worry about code optimisation in compctl emigrated to the
Undying Lands a decade ago (maybe I can still find the postcard...)

Can somebody verify the following is equivalent apart from dealing with
a possible overlapping copy?  I've no way of ensuring this code gets
exercised.

Separately, I seem to be having severe problems with --enable-zsh-mem
with that configuration.  It looked like some failed optimisation
involving realloc().  I think we had something similar a while ago?

Cheers
pws


diff --git a/Src/Zle/compctl.c b/Src/Zle/compctl.c
index fe87409..f963d57 100644
--- a/Src/Zle/compctl.c
+++ b/Src/Zle/compctl.c
@@ -3331,13 +3331,11 @@ makecomplistflags(Compctl cc, char *s, int incmd, int compadd)
 	    zlemetaline[end] = save;
 	    if (brend) {
 		Brinfo bp;
-		char *p;
-		int bl;
 
 		for (bp = brend; bp; bp = bp->next) {
-		    p = lpsuf + (we - zlemetacs) - bp->qpos -
-			(bl = strlen(bp->str));
-		    strcpy(p, p + bl);
+		    char *p2 = lpsuf + (we - zlemetacs) - bp->qpos;
+		    char *p1 = p2 - strlen(bp->str);
+		    memmove(p1, p2, strlen(p2) + 1);
 		}
 	    }
 	    if (!(lpsuf = strchr(lpsuf, '/')) && sf2)


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: -Wrestrict warning on cc 8.3.0
  2019-04-04 10:21   ` Peter Stephenson
@ 2019-04-10  8:48     ` Peter Stephenson
  2019-04-10  8:58       ` Roman Perepelitsa
  0 siblings, 1 reply; 4+ messages in thread
From: Peter Stephenson @ 2019-04-10  8:48 UTC (permalink / raw)
  To: zsh-workers

On Thu, 2019-04-04 at 11:21 +0100, Peter Stephenson wrote:
> On Wed, 2019-04-03 at 20:59 +0200, Wesley Schwengle wrote:
> > 
> > During a make of the latest master I got the following warning:
> >  
> > gcc -c -I. -I../../Src -I../../Src -I../../Src/Zle -I.  -DHAVE_CONFIG_H
> > -DMODULE -Wall -Wmissing-prototypes -O2 -fPIC -o compctl..o compctl.c
> > compctl.c: In function ‘makecomplistflags.isra.6’:
> > compctl.c:3340:7: warning: ‘strcpy’ accessing 1 byte at offsets [0,
> > 9223372036854775807] and [0,9223372036854775807] may overlap 1 byte at
> > offset 0 [-Wrestrict]
> > strcpy(p, p + bl);
> > ^~~~~~~~~~~~~~~~~
> > rm -f compctl.so
> This warning is thoroughly opaque --- and not occurring with a locally
> compiled gcc 8.3.0 on my Ubuntu 16.04 64-bit Intel system --- but the
> code isn't exactly crystal clear, either (subtracting a number off then
> adding it immediately back on again isn't generally regarded as great
> style), and it's quite possible the copy is overlapping.  Also, the last
> person to worry about code optimisation in compctl emigrated to the
> Undying Lands a decade ago (maybe I can still find the postcard...)
> 
> Can somebody verify the following is equivalent apart from dealing with
> a possible overlapping copy?  I've no way of ensuring this code gets
> exercised. 

I've applied this anyway.

pws


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: -Wrestrict warning on cc 8.3.0
  2019-04-10  8:48     ` Peter Stephenson
@ 2019-04-10  8:58       ` Roman Perepelitsa
  0 siblings, 0 replies; 4+ messages in thread
From: Roman Perepelitsa @ 2019-04-10  8:58 UTC (permalink / raw)
  To: Peter Stephenson; +Cc: zsh-workers

[-- Attachment #1: Type: text/plain, Size: 487 bytes --]

On Wed, Apr 10, 2019 at 10:48 AM Peter Stephenson <p.stephenson@samsung.com>
wrote:

> On Thu, 2019-04-04 at 11:21 +0100, Peter Stephenson wrote:
>
> > Can somebody verify the following is equivalent apart from dealing with
> > a possible overlapping copy?  I've no way of ensuring this code gets
> > exercised.
>
> I've applied this anyway.
>

I'm pretty sure your code is equivalent to the original (apart from being
correct if ranges overlap). It's also easier to understand.

Roman.

^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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     [not found] <CGME20190403190049epcas3p4c02406857f7f26510ea8969c969a655e@epcas3p4.samsung.com>
2019-04-03 18:59 ` -Wrestrict warning on cc 8.3.0 Wesley Schwengle
2019-04-04 10:21   ` Peter Stephenson
2019-04-10  8:48     ` Peter Stephenson
2019-04-10  8:58       ` Roman Perepelitsa

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