Re: diffutils 2.8: newlines not ignored under -w

[Paul Eggert]

> From: "Robert A. (Bob) Morris" <address@hidden>
> Date: Fri, 5 Apr 2002 23:40:58 -0500
> 
> If the difference is solely a line with nothing but whitespace
> containing /more/ than just a newline, diff -wB reports a difference,
> as does Solaris diff.

That is how -B is documented to behave.  (Solaris diff doesn't have
-B, so the issue doesn't arise there.)

However, I agree that if -w or -b is specified, then -B should ignore
changes consisting entirely of lines containing only white space.
Here's a patch to do that -- could you please try it out?
This patch is relative to GNU Diffutils 2.8.1, which you can get from:
<ftp://ftp.gnu.org/gnu/diffutils/diffutils-2.8.1.tar.gz>
(There also needs to be a change to the documentation.)

===================================================================
RCS file: src/RCS/util.c,v
retrieving revision 1.31
diff -pu -r1.31 src/util.c
--- src/util.c  2002/02/28 05:22:26     1.31
+++ src/util.c  2002/04/06 06:59:52
@@ -655,6 +655,8 @@ analyze_hunk (struct change *hunk,
   size_t trivial_length = (int) ignore_blank_lines - 1;
     /* If 0, ignore zero-length lines;
        if SIZE_MAX, do not ignore lines just because of their length.  */
+  bool skip_leading_white_space =
+    (ignore_blank_lines && IGNORE_SPACE_CHANGE <= ignore_white_space);
 
   char const * const *linbuf0 = files[0].linbuf;  /* Help the compiler.  */
   char const * const *linbuf1 = files[1].linbuf;
@@ -675,8 +677,13 @@ analyze_hunk (struct change *hunk,
       for (i = next->line0; i <= l0 && trivial; i++)
        {
          char const *line = linbuf0[i];
-         size_t len = linbuf0[i + 1] - line - 1;
-         if (len != trivial_length
+         char const *newline = linbuf0[i + 1] - 1;
+         size_t len = newline - line;
+         char const *p = line;
+         if (skip_leading_white_space)
+           while (ISSPACE ((unsigned char) *p) && *p != '\n')
+             p++;
+         if (newline - p != trivial_length
              && (! ignore_regexp.fastmap
                  || re_search (&ignore_regexp, line, len, 0, len, 0) < 0))
            trivial = 0;
@@ -685,8 +692,13 @@ analyze_hunk (struct change *hunk,
       for (i = next->line1; i <= l1 && trivial; i++)
        {
          char const *line = linbuf1[i];
-         size_t len = linbuf1[i + 1] - line - 1;
-         if (len != trivial_length
+         char const *newline = linbuf1[i + 1] - 1;
+         size_t len = newline - line;
+         char const *p = line;
+         if (skip_leading_white_space)
+           while (ISSPACE ((unsigned char) *p) && *p != '\n')
+             p++;
+         if (newline - p != trivial_length
              && (! ignore_regexp.fastmap
                  || re_search (&ignore_regexp, line, len, 0, len, 0) < 0))
            trivial = 0;