[PATCH v2] column: disallow negative padding

[Kristoffer Haugsbakk <code@khaugsbakk.name>]

A negative padding does not make sense and can cause errors in the
memory allocator since it’s interpreted as an unsigned integer.

Disallow negative padding. Also guard against negative padding in
`column.c` where it is conditionally used.

Reported-by: Tiago Pascoal <tiago@pascoal.net>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
---

Notes (series):
    v2:
    • Incorporate Junio’s changes (guard against negative padding in
      `column.c`)
    • Tweak commit message based on Junio’s analysis
    • Use gettext for error message
      • However I noticed that the “translation string” from `fast-import`
        isn’t a translation string. So let’s invent a new one and use a
        parameter so that it can be used elsewhere.
    • Make a test

 builtin/column.c  |  2 ++
 column.c          |  4 ++--
 t/t9002-column.sh | 11 +++++++++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/builtin/column.c b/builtin/column.c
index e80218f81f9..10ff7e01668 100644
--- a/builtin/column.c
+++ b/builtin/column.c
@@ -45,6 +45,8 @@ int cmd_column(int argc, const char **argv, const char *prefix)
 	memset(&copts, 0, sizeof(copts));
 	copts.padding = 1;
 	argc = parse_options(argc, argv, prefix, options, builtin_column_usage, 0);
+	if (copts.padding < 0)
+		die(_("%s must be non-negative"), "--padding");
 	if (argc)
 		usage_with_options(builtin_column_usage, options);
 	if (real_command || command) {
diff --git a/column.c b/column.c
index ff2f0abf399..c723428bc70 100644
--- a/column.c
+++ b/column.c
@@ -189,7 +189,7 @@ void print_columns(const struct string_list *list, unsigned int colopts,
 	memset(&nopts, 0, sizeof(nopts));
 	nopts.indent = opts && opts->indent ? opts->indent : "";
 	nopts.nl = opts && opts->nl ? opts->nl : "\n";
-	nopts.padding = opts ? opts->padding : 1;
+	nopts.padding = (opts && 0 <= opts->padding) ? opts->padding : 1;
 	nopts.width = opts && opts->width ? opts->width : term_columns() - 1;
 	if (!column_active(colopts)) {
 		display_plain(list, "", "\n");
@@ -373,7 +373,7 @@ int run_column_filter(int colopts, const struct column_options *opts)
 		strvec_pushf(argv, "--width=%d", opts->width);
 	if (opts && opts->indent)
 		strvec_pushf(argv, "--indent=%s", opts->indent);
-	if (opts && opts->padding)
+	if (opts && 0 <= opts->padding)
 		strvec_pushf(argv, "--padding=%d", opts->padding);
 
 	fflush(stdout);
diff --git a/t/t9002-column.sh b/t/t9002-column.sh
index 348cc406582..d5b98e615bc 100755
--- a/t/t9002-column.sh
+++ b/t/t9002-column.sh
@@ -196,4 +196,15 @@ EOF
 	test_cmp expected actual
 '
 
+test_expect_success 'padding must be non-negative' '
+	cat >input <<\EOF &&
+1 2 3 4 5 6
+EOF
+	cat >expected <<\EOF &&
+fatal: --padding must be non-negative
+EOF
+	test_must_fail git column --mode=column --padding=-1 <input >actual 2>&1 &&
+	test_cmp expected actual
+'
+
 test_done
-- 
2.43.0