Re: [PATCH] patch: handle files with no final newline

Applied, thank you.

On Sun, Apr 19, 2026 at 11:03 AM Ron Yorston via busybox
<[email protected]> wrote:
>
> GNU and BSD patch both handle patches which include the annotation
> '\ No newline at end of file'.  BusyBox patch doesn't, even though
> its diff emits it.
>
> Implement this feature and add some tests.
>
> function                                             old     new   delta
> patch_main                                          1912    2002     +90
> do_line                                               88     116     +28
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 2/0 up/down: 118/0)             Total: 118 bytes
>
> Signed-off-by: Ron Yorston <[email protected]>
> ---
>  editors/patch.c       | 33 ++++++++++++++++++++---
>  testsuite/patch.tests | 63 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 92 insertions(+), 4 deletions(-)
>
> diff --git a/editors/patch.c b/editors/patch.c
> index 5a768b23f..ee0ccd384 100644
> --- a/editors/patch.c
> +++ b/editors/patch.c
> @@ -57,6 +57,7 @@ struct double_list {
>         struct double_list *next;
>         struct double_list *prev;
>         char *data;
> +       int no_newline;
>  };
>
>  // Free all the elements of a linked list
> @@ -76,7 +77,7 @@ static void dlist_free(struct double_list *list, void (*freeit)(void *data))
>  static struct double_list *dlist_add(struct double_list **list, char *data)
>  {
>         struct double_list *llist;
> -       struct double_list *line = xmalloc(sizeof(*line));
> +       struct double_list *line = xzalloc(sizeof(*line));
>
>         line->data = data;
>         llist = *list;
> @@ -140,7 +141,8 @@ static void do_line(void *data)
>
>         if (TT.state > 1 && *dlist->data != TT.state)
>                 fdprintf(TT.state == 2 ? 2 : TT.fileout,
> -                       "%s\n", dlist->data + (TT.state > 3 ? 1 : 0));
> +                       dlist->no_newline && TT.state != 2 ? "%s" : "%s\n",
> +                       dlist->data + (TT.state > 3 ? 1 : 0));
>
>         if (PATCH_DEBUG) fdprintf(2, "DO %d: %s\n", TT.state, dlist->data);
>
> @@ -433,7 +435,17 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
>
>                 // Are we assembling a hunk?
>                 if (state >= 2) {
> -                       if (*patchline == ' ' || *patchline == '+' || *patchline == '-') {
> +                       switch (*patchline) {
> +                       case '\\':
> +                               // '\ No newline at end of file' detected, mark
> +                               // previous line, if it exists.
> +                               if (TT.current_hunk->prev)
> +                                       TT.current_hunk->prev->no_newline = TRUE;
> +                               free(patchline);
> +                               continue;
> +                       case ' ':
> +                       case '+':
> +                       case '-':
>                                 dlist_add(&TT.current_hunk, patchline);
>
>                                 if (*patchline != '+') oldlen--;
> @@ -445,7 +457,20 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
>
>                                 // If we've consumed all expected hunk lines, apply the hunk.
>
> -                               if (!oldlen && !newlen) state = apply_one_hunk();
> +                               if (!oldlen && !newlen) {
> +                                       // Peek ahead for '\ No newline at end of file', mark
> +                                       // previous line, if it exists.
> +                                       int c = getchar();
> +                                       ungetc(c, stdin);
> +                                       if (c == '\\') {
> +                                               if (TT.current_hunk->prev)
> +                                                       TT.current_hunk->prev->no_newline = TRUE;
> +                                               do {
> +                                                       c = getchar();
> +                                               } while (c != EOF && c != '\n');
> +                                       }
> +                                       state = apply_one_hunk();
> +                               }
>                                 continue;
>                         }
>                         fail_hunk();
> diff --git a/testsuite/patch.tests b/testsuite/patch.tests
> index 1d48e90be..1a786aa71 100755
> --- a/testsuite/patch.tests
> +++ b/testsuite/patch.tests
> @@ -287,6 +287,69 @@ bar
>  2.9.2
>  " \
>
> +# testing "test name" "command(s)" "expected result" "file input" "stdin"
> +testing "patch file with no last newline" \
> +       'patch 2>&1; cat input' \
> +"\
> +patching file input
> +first line
> +last line with newline
> +" \
> +"\
> +first line
> +last line with no newline" \
> +"\
> +--- input
> ++++ input
> +@@ -1,2 +1,2 @@
> + first line
> +-last line with no newline
> +\ No newline at end of file
> ++last line with newline
> +" \
> +
> +# testing "test name" "command(s)" "expected result" "file input" "stdin"
> +testing "patch -R to revert previous test" \
> +       'patch -R 2>&1; cat input' \
> +"\
> +patching file input
> +first line
> +last line with no newline" \
> +"\
> +first line
> +last line with newline
> +" \
> +"\
> +--- input
> ++++ input
> +@@ -1,2 +1,2 @@
> + first line
> +-last line with no newline
> +\ No newline at end of file
> ++last line with newline
> +" \
> +
> +# testing "test name" "command(s)" "expected result" "file input" "stdin"
> +testing "patch file so it has no last newline" \
> +       'patch 2>&1; cat input' \
> +"\
> +patching file input
> +first line
> +last line with no newline" \
> +"\
> +first line
> +last line with newline
> +" \
> +"\
> +--- input
> ++++ input
> +@@ -1,2 +1,2 @@
> + first line
> +-last line with newline
> ++last line with no newline
> +\ No newline at end of file
> +" \
> +
>  rm input.orig 2>/dev/null
>
>  exit $FAILCOUNT
> --
> 2.53.0
>
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