[glibc] localedef: Use initializer for flexible array member [BZ #24950]

[Florian Weimer <fw at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1471fa556afb428c4a4c46cf5543a4101d5bcf91

commit 1471fa556afb428c4a4c46cf5543a4101d5bcf91
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Sep 3 14:01:39 2019 +0200

    localedef: Use initializer for flexible array member [BZ #24950]
    
    struct charseq used a zero-length array instead of a flexible array
    member.  This required a strange construct to initialize struct
    charseq objects, and GCC 10 warns about that:
    
    cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
    In file included from programs/repertoire.h:24,
                     from programs/localedef.h:32,
                     from programs/ld-ctype.c:35:
    programs/charmap.h:63:17: note: destination object declared here
       63 |   unsigned char bytes[0];
          |                 ^~~~~
    cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
    programs/charmap.h:63:17: note: destination object declared here
    cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
    programs/charmap.h:63:17: note: destination object declared here
    cc1: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
    programs/charmap.h:63:17: note: destination object declared here
    
    The change makes the object physically const, but it is not expected
    to be modified.

Diff:
---
 ChangeLog                  |  8 ++++++++
 locale/programs/charmap.h  |  2 +-
 locale/programs/ld-ctype.c | 12 ++++++------
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 67ec991..e215c4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-09-03  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #24950]
+	* locale/programs/charmap.h (struct charseq): Turn bytes into a
+	flexible array member.
+	* locale/programs/ld-ctype.c (ctype_finish): Use initializer for
+	replace.
+
 2019-09-02  Florian Weimer  <fweimer@redhat.com>
 
 	* misc/tst-mntent-autofs.c: New file.
diff --git a/locale/programs/charmap.h b/locale/programs/charmap.h
index 870a9e9..70db330 100644
--- a/locale/programs/charmap.h
+++ b/locale/programs/charmap.h
@@ -60,7 +60,7 @@ struct charseq
   const char *name;
   uint32_t ucs4;
   int nbytes;
-  unsigned char bytes[0];
+  unsigned char bytes[];
 };
 
 
diff --git a/locale/programs/ld-ctype.c b/locale/programs/ld-ctype.c
index cfc9c43..9123f64 100644
--- a/locale/programs/ld-ctype.c
+++ b/locale/programs/ld-ctype.c
@@ -842,8 +842,6 @@ no input digits defined and none of the standard names in the charmap"));
   for (cnt = 0; cnt < 10; ++cnt)
     if (ctype->mboutdigits[cnt] == NULL)
       {
-	static struct charseq replace[2];
-
 	if (!warned)
 	  {
 	    record_error (0, 0, _("\
@@ -851,10 +849,12 @@ not all characters used in `outdigit' are available in the charmap"));
 	    warned = 1;
 	  }
 
-	replace[0].nbytes = 1;
-	replace[0].bytes[0] = '?';
-	replace[0].bytes[1] = '\0';
-	ctype->mboutdigits[cnt] = &replace[0];
+	static const struct charseq replace =
+	  {
+	     .nbytes = 1,
+	     .bytes = "?",
+	  };
+	ctype->mboutdigits[cnt] = (struct charseq *) &replace;
       }
 
   warned = 0;