Re: [BUG]: backfill min batch size test case failure on s390x

From

PPPranav P <pranav.p7@ibm.com>

Date

Apr 22, 2025, 12:35 UTC

Message-ID

<BY5PR15MB35398BF51EAFC520421163AFA0BB2@BY5PR15MB3539.namprd15.prod.outlook.com>

In-Reply-To

<BY5PR15MB35396BEBCAB2C559080F08C6A0BB2@BY5PR15MB3539.namprd15.prod.outlook.com>

Hi,

diff --git a/builtin/backfill.c b/builtin/backfill.c
index 33e1ea2f84..18f9701487 100644
--- a/builtin/backfill.c
+++ b/builtin/backfill.c
@@ -123,7 +123,7 @@ int cmd_backfill(int argc, const char **argv, const char *prefix, struct reposit
                .sparse = 0,
        };
        struct option options[] = {
-               OPT_INTEGER(0, "min-batch-size", &ctx.min_batch_size,
+               OPT_MAGNITUDE(0, "min-batch-size", &ctx.min_batch_size,
                            N_("Minimum number of objects to request at a time")),
                OPT_BOOL(0, "sparse", &ctx.sparse,
                         N_("Restrict the missing objects to the current sparse-checkout")),
--

Thanks,
Pranav

________________________________________
From: Pranav P
Sent: Tuesday, April 22, 2025 6:01 PM
To: git@vger.kernel.org
Subject: [BUG]: backfill min batch size test case failure on s390x

Hi,

When running `make test` on an s390x machine in Debian it is failing on 'do partial clone 2, backfill min batch size'
Reference: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1102106

After processing the command line arguments structure member min_batch_size should have had the value 20

Instead of having the value 20 (--min-batch-size=20) it was having a very large value

min_batch_size in `struct backfill_context` is of type `size_t` and since in the function cmd_backfill, in the
options struct it is passed on to OPT_INTEGER, which eventually causes

```
*(int *)opt->value = strtol(arg, (char **)&s, 10);
```
in parse-options.c line 188. This is writing the data in the first 4 bytes of min_batch_size and on big endian
systems this will lead min_batch_size to be a big number. This issue is immediately visible in little endian systems.

Changing OPT_INTEGER to OPT_MAGNITUDE seems to be working on x86 and s390x

```
diff --git a/builtin/backfill.c b/builtin/backfill.c
index 18f9701487..33e1ea2f84 100644
--- a/builtin/backfill.c
+++ b/builtin/backfill.c
@@ -123,7 +123,7 @@ int cmd_backfill(int argc, const char **argv, const char *prefix, struct reposit
                .sparse = 0,
        };
        struct option options[] = {
-               OPT_MAGNITUDE(0, "min-batch-size", &ctx.min_batch_size,
+               OPT_INTEGER(0, "min-batch-size", &ctx.min_batch_size,
                            N_("Minimum number of objects to request at a time")),
                OPT_BOOL(0, "sparse", &ctx.sparse,
                         N_("Restrict the missing objects to the current sparse-checkout")),
```

But on systems where size_t which not be unsigned long, this might lead to an issue.
So, one other suggestion I have is to change the data type of min_batch_size from size_t to int. But I am not able to
determine whether a practical upper bound for min_batch_size would exceed what an int variable can store.
With that clarification, I can a raise patch for the issue.

Please review the rest of the bug report below.

[System Info]
git version:
git version 2.49.0.391.g4bbb303af6
cpu: s390x
built from commit: 4bbb303af69990ccd05fe3a2eb58a1ce036f8220
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
libcurl: 8.13.0
OpenSSL: OpenSSL 3.4.1 11 Feb 2025
zlib: 1.3.1
SHA-1: SHA1_DC
SHA-256: SHA256_BLK
uname: Linux 6.1.0-31-s390x #1 SMP Debian 6.1.128-1 (2025-02-07) s390x
compiler info: gnuc: 14.2
libc info: glibc: 2.41
$SHELL (typically, interactive shell): /bin/bash


[Enabled Hooks]

I am fairly new to opensource and was following the `git bugreport`. So I am extremely sorry for any lack of clarity in the report.

Thanks,
Pranav