Re: [PATCH] apply.c: fix -p argument parsing

> "git apply" has an option -p that takes an integer as its argument.
> Unfortunately the function apply_option_parse_p() in charge of parsing
> this argument uses atoi() to convert from string to integer, which
> allows a non-digit after the number (e.g. "1q") to be silently ignored.
> As a consequence, an argument that does not begin with a digit silently
> becomes a zero. Despite this command working fine when a non-positive
> argument is passed, it might be useful for the end user to know that
> their input contains non-digits that might've been unintended.
>
> Replace atoi() with strtol_i() to catch malformed inputs.
>
> Signed-off-by: Mirko Faina <mroik@delayed.space>
> ---
> Unlike [1], this argument doesn't overwrite an argument initialized to a
> default value. Instead state->p_value_known is used instead to see if
> the p_value should be used.

>
> [1] https://lore.kernel.org/git/xmqq5y181fx0.fsf_-_@gitster.g/
>
>  apply.c               |  3 ++-
>  t/meson.build         |  1 +
>  t/t4142-apply-args.sh | 31 +++++++++++++++++++++++++++++++
>  t/t4142/patch         | 16 ++++++++++++++++
>  4 files changed, 50 insertions(+), 1 deletion(-)
>  create mode 100755 t/t4142-apply-args.sh
>  create mode 100644 t/t4142/patch
>
> diff --git a/apply.c b/apply.c
> index b6dd1066a0..b6c9e40700 100644
> --- a/apply.c
> +++ b/apply.c
> @@ -4981,7 +4981,8 @@ static int apply_option_parse_p(const struct option *opt,
>  
>  	BUG_ON_OPT_NEG(unset);
>  
> -	state->p_value = atoi(arg);
> +	if (strtol_i(arg, 10, &state->p_value) < 0 || state->p_value < 0)
> +		die("<num> has to be non negative an integer");
>  	state->p_value_known = 1;
>  	return 0;
>  }
> diff --git a/t/meson.build b/t/meson.build
> index 106c68df3d..d26df707cb 100644
> --- a/t/meson.build
> +++ b/t/meson.build
> @@ -547,6 +547,7 @@ integration_tests = [
>    't4139-apply-escape.sh',
>    't4140-apply-ita.sh',
>    't4141-apply-too-large.sh',
> +  't4142-apply-args.sh',
>    't4150-am.sh',
>    't4151-am-abort.sh',
>    't4152-am-subjects.sh',
> diff --git a/t/t4142-apply-args.sh b/t/t4142-apply-args.sh
> new file mode 100755
> index 0000000000..6fe73289f2
> --- /dev/null
> +++ b/t/t4142-apply-args.sh
> @@ -0,0 +1,31 @@
> +#!/bin/bash
> +
> +test_description='git apply test for various malformed arguments
> +'
> +
> +. ./test-lib.sh
> +
> +test_expect_success setup '
> +	git commit --allow-empty -m "Initial commit"
> +'
> +
> +test_expect_success 'git apply -p 1 patch' '
> +	test_when_finished "rm -rf result t" &&
> +	git apply -p 1 $TEST_DIRECTORY/t4142/patch &&
> +	ls -l >result &&
> +	test_line_count = 3 result
> +'
> +
> +test_expect_success 'git apply -p malformed patch' '
> +	test_must_fail git apply -p malformed $TEST_DIRECTORY/t4142/patch
> +'
> +
> +test_expect_success 'git apply -p 2q patch' '
> +	test_must_fail git apply -p 2q $TEST_DIRECTORY/t4142/patch
> +'
> +
> +test_expect_success 'git apply -p -1 patch' '
> +	test_must_fail git apply -p -1 $TEST_DIRECTORY/t4142/patch
> +'
> +
> +test_done
> diff --git a/t/t4142/patch b/t/t4142/patch
> new file mode 100644
> index 0000000000..c4511bb708
> --- /dev/null
> +++ b/t/t4142/patch
> @@ -0,0 +1,16 @@
> +From 90ad11d5b2d437e82d4d992f72fb44c2227798b5 Mon Sep 17 00:00:00 2001
> +From: Mroik <mroik@delayed.space>
> +Date: Mon, 9 Mar 2026 23:25:00 +0100
> +Subject: [PATCH] Test
> +
> +---
> + t/test/test | 0
> + 1 file changed, 0 insertions(+), 0 deletions(-)
> + create mode 100644 t/test/test
> +
> +diff --git a/t/test/test b/t/test/test
> +new file mode 100644
> +index 0000000000..e69de29bb2
> +-- 
> +2.53.0.851.ga537e3e6e9
> +