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From: "amodra at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/28865] Structures with a flexible arrray member have wrong .size
Date: Sat, 04 May 2013 14:34:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28865

--- Comment #9 from Alan Modra <amodra at gmail dot com> 2013-05-04 14:34:39 UTC ---
>>From what I see on current mainline for a testcase based on
glibc/nss/nss_files/files-init.c the var_decl size and the type size agree and
are correct.  What causes a problem with -fsection-anchors is that the actual
data emitted by output_constant() is wrong.

struct traced_file
{
  long pad;
  char fname[];
};

#define TF(id, filename, ...)                    \
union                                \
{                                \
  struct traced_file file;                    \
  char buf[sizeof (struct traced_file) + sizeof (filename)];    \
} id##_traced_file =                        \
  {                                \
    .file =                            \
    {                                \
      .fname = filename                        \
    }                                \
  }

TF (pwd, "/etc/passwd");
TF (grp, "/etc/group");

Gives me

    .file    "unioninit.c"
    .globl grp_traced_file
    .globl pwd_traced_file
    .section    ".data"
    .align 2
.LANCB0:
    .org .LANCB0+0
    .type    grp_traced_file, @object
    .size    grp_traced_file, 16
grp_traced_file:
    .zero    4
    .string    "/etc/group"
    .zero    12
    .org .LANCB0+16
    .type    pwd_traced_file, @object
    .size    pwd_traced_file, 16
pwd_traced_file:
    .zero    4
    .string    "/etc/passwd"
    .zero    12
    .ident    "GCC: (GNU) 4.9.0 20130502 (experimental)"
    .section    .note.GNU-stack,"",@progbits

Those ".zero 12" lines shouldn't be there.