fprintf: Deal with zero sized arrays in the midle of a union

gcc dislikes invalid C:

  /home/acme/git/build/v5.1-rc4+/fs/ceph/export.o
  /tmp/fullcircle.CvAfpM.c:591:22: error: flexible array member in union
     __u32              raw[];                /*     0     0 */
                        ^~~
Before:

  $ pahole -C fid /home/acme/git/build/v5.1-rc4+/fs/ceph/export.o
  struct fid {
  	union {
  		struct {
  			u32        ino;                  /*     0     4 */
  			u32        gen;                  /*     4     4 */
  			u32        parent_ino;           /*     8     4 */
  			u32        parent_gen;           /*    12     4 */
  		} i32;                                   /*     0    16 */
  		struct {
  			u32        block;                /*     0     4 */
  			u16        partref;              /*     4     2 */
  			u16        parent_partref;       /*     6     2 */
  			u32        generation;           /*     8     4 */
  			u32        parent_block;         /*    12     4 */
  			u32        parent_generation;    /*    16     4 */
  		} udf;                                   /*     0    20 */
  		__u32              raw[];                /*     0     0 */
  	};                                               /*     0    20 */

  	/* size: 20, cachelines: 1, members: 1 */
  	/* last cacheline: 20 bytes */
  };
  $

After:

  $ pahole -C fid /home/acme/git/build/v5.1-rc4+/fs/ceph/export.o
  struct fid {
  	union {
  		struct {
  			u32        ino;                  /*     0     4 */
  			u32        gen;                  /*     4     4 */
  			u32        parent_ino;           /*     8     4 */
  			u32        parent_gen;           /*    12     4 */
  		} i32;                                   /*     0    16 */
  		struct {
  			u32        block;                /*     0     4 */
  			u16        partref;              /*     4     2 */
  			u16        parent_partref;       /*     6     2 */
  			u32        generation;           /*     8     4 */
  			u32        parent_block;         /*    12     4 */
  			u32        parent_generation;    /*    16     4 */
  		} udf;                                   /*     0    20 */
  		__u32              raw[0];               /*     0     0 */
  	};                                               /*     0    20 */

  	/* size: 20, cachelines: 1, members: 1 */
  	/* last cacheline: 20 bytes */
  };
  $

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2 files changed