From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
Subject: bug#30820: Chunked store references in compiled code break grafting
	(again)
Date: Mon, 19 Mar 2018 23:29:10 +0100
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References: <87o9jq7j7r.fsf@gnu.org> <87efkm7eov.fsf@gnu.org>
	<20180319222205.2e35f26f@scratchpost.org>
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To: Danny Milosavljevic <dannym@scratchpost.org>
Cc: 30820@debbugs.gnu.org

Heya,

Danny Milosavljevic <dannym@scratchpost.org> skribis:

>> The second issue is that the patch only ever worked with literal
>> strings.  It does not =E2=80=9Csee=E2=80=9D strings in constant arrays l=
ike the =E2=80=98str=E2=80=99
>> array in the example above.
>>=20
>> The gconv-module file name mentioned in the first message in this bug
>> report is an example of a string assigned to a static array, in
>> iconv/gconv_conf.c:
>>=20
>>   /* This is the default path where we look for module lists.  */
>>   static const char default_gconv_path[] =3D GCONV_PATH;
>
> I don't understand why this is a problem.  Grafting would just
> mutate default_gconv_path, right?  Who cares how the runtime memcpy
> works (if there's no literal as source)?

At compile-time, GCC finds out that =E2=80=98default_gconv_path=E2=80=99 is=
 used only
in one place, in an strcpy call.  Thus, it chooses to use the movabs
optimization, and as a consequence, to split =E2=80=98default_gconv_path=E2=
=80=99 in
8-byte chunks.  It can do so because it=E2=80=99s =E2=80=98static=E2=80=99.

Ludo=E2=80=99.