From ea01f254b4e0dc2f59db4cba9dd4fa98e9f5b2e5 Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Thu, 13 Nov 2025 07:50:50 +0000
Subject: paste: fix output when file lengths differ

If the files being pasted had different numbers of lines the
output was incorrect.

Rewrite the loop over all lines to allow for this.  Add tests for
such conditions.

function                                             old     new   delta
paste_main                                           458     526     +68

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
 coreutils/paste.c                | 36 ++++++++++++++++++++++++------------
 testsuite/paste/paste-long-short | 19 +++++++++++++++++++
 testsuite/paste/paste-short-long | 19 +++++++++++++++++++
 3 files changed, 62 insertions(+), 12 deletions(-)
 create mode 100644 testsuite/paste/paste-long-short
 create mode 100644 testsuite/paste/paste-short-long

diff --git a/coreutils/paste.c b/coreutils/paste.c
index 3e5f20158..363340e3d 100644
--- a/coreutils/paste.c
+++ b/coreutils/paste.c
@@ -34,27 +34,38 @@
 
 static void paste_files(FILE** files, int file_cnt, char* delims, int del_cnt)
 {
-	char *line;
+	char **line = xmalloc(file_cnt * sizeof(char *));
 	char delim;
 	int active_files = file_cnt;
 	int i;
 
 	while (active_files > 0) {
 		int del_idx = 0;
+		int got_line = FALSE;
 
 		for (i = 0; i < file_cnt; ++i) {
-			if (files[i] == NULL)
-				continue;
-
-			line = xmalloc_fgetline(files[i]);
-			if (!line) {
-				fclose_if_not_stdin(files[i]);
-				files[i] = NULL;
-				--active_files;
-				continue;
+			if (files[i]) {
+				line[i] = xmalloc_fgetline(files[i]);
+				if (!line[i]) {
+					fclose_if_not_stdin(files[i]);
+					files[i] = NULL;
+					--active_files;
+				} else {
+					got_line = TRUE;
+				}
+			} else {
+				line[i] = NULL;
+			}
+		}
+
+		if (!got_line)
+			break;
+
+		for (i = 0; i < file_cnt; ++i) {
+			if (line[i]) {
+				fputs_stdout(line[i]);
+				free(line[i]);
 			}
-			fputs_stdout(line);
-			free(line);
 			delim = '\n';
 			if (i != file_cnt - 1) {
 				delim = delims[del_idx++];
@@ -65,6 +76,7 @@ static void paste_files(FILE** files, int file_cnt, char* delims, int del_cnt)
 				fputc(delim, stdout);
 		}
 	}
+	free(line);
 }
 
 static void paste_files_separate(FILE** files, char* delims, int del_cnt)
diff --git a/testsuite/paste/paste-long-short b/testsuite/paste/paste-long-short
new file mode 100644
index 000000000..e626d730e
--- /dev/null
+++ b/testsuite/paste/paste-long-short
@@ -0,0 +1,19 @@
+cat > foo <<EOF
+foo1
+foo2
+foo3
+EOF
+
+cat > bar <<EOF
+bar1
+bar2
+EOF
+
+cat > baz <<EOF
+foo1	bar1
+foo2	bar2
+foo3	
+EOF
+
+busybox paste foo bar > qux
+diff -u baz qux
diff --git a/testsuite/paste/paste-short-long b/testsuite/paste/paste-short-long
new file mode 100644
index 000000000..785da60a7
--- /dev/null
+++ b/testsuite/paste/paste-short-long
@@ -0,0 +1,19 @@
+cat > foo <<EOF
+foo1
+foo2
+EOF
+
+cat > bar <<EOF
+bar1
+bar2
+bar3
+EOF
+
+cat > baz <<EOF
+foo1	bar1
+foo2	bar2
+	bar3
+EOF
+
+busybox paste foo bar > qux
+diff -u baz qux
-- 
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