From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?UTF-8?Q?Court=C3=A8s?=)
Subject: bug#30395: bug#30820: Chunked store references in compiled code break
	grafting (again)
Date: Fri, 16 Mar 2018 09:54:31 +0100
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ludo@gnu.org (Ludovic Court=C3=A8s) skribis:

> void foo (char *x, char *y)
> {
>   /* MEMCPY (x, str, sizeof str); */
>   MEMCPY (y, "this is a literal /gnu/store string", 35);
> }

This was not a correct example because =E2=80=9C/gnu/store=E2=80=9D must be=
 followed by
at least 34 chars for the patch to work.  And indeed, it does work in
this case:

--8<---------------cut here---------------start------------->8---
$ cat strmov.c
#define _GNU_SOURCE
#include <string.h>
static const char str[] =3D "MEMpCPY /gnu/store/THIS IS A LONG STRING, A VE=
RY, VERY, VERY LOOOOONG STRING";

extern char *p, *q;

#ifndef MEMCPY
# define MEMCPY memcpy
#endif

void foo (char *x, char *y)
{
  /* MEMCPY (x, str, sizeof str); */
  MEMCPY (y, "this is a literal /gnu/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee=
ee string", 35);
}
$ guix environment --ad-hoc gcc-toolchain@5 -C -- gcc -O2 -c strmov.c
$ objdump -S strmov.o |grep movabs
--8<---------------cut here---------------end--------------->8---

So the real issue is this:

> 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 li=
ke the =E2=80=98str=E2=80=99
> array in the example above.

Ludo=E2=80=99.