Subject: bug#19508: [bug-diffutils] bug#19508: [PATCH] diff: compare major, minor numbers of block/character special files

From: Ondřej Svoboda <[email-masked]>
Date: Thu, 12 Feb 2015 00:40:15 +0100

Paul, this is the first patch in the series (and is succeeded by the 
fifo one), I am sorry for the confusion.

Could you please give it a look?

Thanks :-)
Ondra Svoboda

On 4.1.2015 21:51, Ondřej Svoboda wrote:
> This deals with situation such as
>
>   File dev1/block1 is a block special file while file dev2/block1 is
>   a block special file
>
> in case the major and minor numbers are identical.
> If stat.st_rdev does not match, a message is given:
>
>   Block special files dev1/block1 and dev2/block1 differ: 1,2 (3,2)
> ---
>  src/diff.c | 23 +++++++++++++++++++++++
>  src/diff.h |  1 +
>  src/util.c |  9 +++++++++
>  3 files changed, 33 insertions(+)
>
> diff --git a/src/diff.c b/src/diff.c
> index ff28377..a3e1b6f 100644
> --- a/src/diff.c
> +++ b/src/diff.c
> @@ -1276,6 +1276,29 @@ compare_files (struct comparison const *parent,
>            status = EXIT_FAILURE;
>          }
>      }
> +      else if ((S_ISBLK (cmp.file[0].stat.st_mode)
> +            && S_ISBLK (cmp.file[1].stat.st_mode))
> +           || (S_ISCHR (cmp.file[0].stat.st_mode)
> +               && S_ISCHR (cmp.file[1].stat.st_mode)))
> +    {
> +      if (cmp.file[0].stat.st_rdev != cmp.file[1].stat.st_rdev)
> +        {
> +          char major_minor0[20], major_minor1[20];
> +          format_major_minor (major_minor0, cmp.file[0].stat.st_rdev);
> +          format_major_minor (major_minor1, cmp.file[1].stat.st_rdev);
> +
> +          const char *message = S_ISBLK (cmp.file[0].stat.st_mode) ?
> +            "Block special files %s and %s differ: %s (%s)\n" :
> +            "Character special files %s and %s differ: %s (%s)\n";
> +          message5 (message,
> +            file_label[0] ? file_label[0] : cmp.file[0].name,
> +            file_label[1] ? file_label[1] : cmp.file[1].name,
> +            major_minor0, major_minor1);
> +
> +          /* This is a difference.  */
> +          status = EXIT_FAILURE;
> +        }
> +    }
>        else
>      {
>        /* We have two files that are not to be compared.  */
> diff --git a/src/diff.h b/src/diff.h
> index 465e4bc..098e75f 100644
> --- a/src/diff.h
> +++ b/src/diff.h
> @@ -390,3 +390,4 @@ extern void print_script (struct change *, struct 
> change * (*) (struct change *)
>  extern void setup_output (char const *, char const *, bool);
>  extern void translate_range (struct file_data const *, lin, lin,
>                               long int *, long int *);
> +extern void format_major_minor (char *buffer, const dev_t st_rdev);
> diff --git a/src/util.c b/src/util.c
> index 2d6d3fc..4773003 100644
> --- a/src/util.c
> +++ b/src/util.c
> @@ -24,6 +24,7 @@
>  #include <system-quote.h>
>  #include <xalloc.h>
>  #include "xvasprintf.h"
> +#include <sys/types.h>
>   char const pr_program[] = PR_PROGRAM;
>  @@ -907,3 +908,11 @@ debug_script (struct change *sp)
>     fflush (stderr);
>  }
> +
> +/* Format a device number as major,minor. */
> +
> +void
> +format_major_minor (char *buffer, const dev_t st_rdev)
> +{
> +  sprintf (buffer, "%u,%u", (major (st_rdev)), (minor (st_rdev)));
> +}