From 35cbd6e0255c27c7c5371ec9f7ba80959cb46f5c Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sun, 25 Oct 2026 18:22:30 -0700 Subject: [PATCH] tar: make GNUSparseFile headers reproducible MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Follow libarchive’s lead in using names of the form "%d/GNUSparseFile.0/%f", not "%d/GNUSparseFile.%p/%f", when building archives. This makes the output reproducible. Problem reported by Johannes Schauer Marin Rodrigues in: https://lists.gnu.org/r/bug-tar/2026-10/msg00009.html * src/sparse.c (pax_dump_header_0, pax_dump_header_1): Use "0", not "%p", in the format of a GNUSparseFile header. --- src/sparse.c | 9 +++++---- 4 files changed, 24 insertions(+), 22 deletions(-) diff --git a/src/sparse.c b/src/sparse.c index 050d91da..16abe9f3 100644 --- a/src/sparse.c +++ b/src/sparse.c @@ -1014,7 +1014,8 @@ static struct tar_sparse_optab const star_optab = { GNU.sparse.size variable) The name field of the ustar header is constructed using the pattern - "%d/GNUSparseFile.%p/%f". + "%d/GNUSparseFile.0/%f". Although the pattern formerly used "%p" + instead of "0", the "%p" hurt reproducibility. The sparse map itself is stored in the file data block, preceding the actual file data. It consists of a series of octal numbers of arbitrary length, @@ -1082,8 +1083,8 @@ pax_dump_header_0 (struct tar_sparse_file *file) { xheader_store ("GNU.sparse.name", file->stat_info, NULL); save_file_name = file->stat_info->file_name; - file->stat_info->file_name = xheader_format_name (file->stat_info, - "%d/GNUSparseFile.%p/%f", 0); + file->stat_info->file_name + = xheader_format_name (file->stat_info, "%d/GNUSparseFile.0/%f", 0); xheader_string_begin (&file->stat_info->xhdr); for (i = 0; i < file->stat_info->sparse_map_avail; i++) @@ -1182,7 +1183,7 @@ pax_dump_header_1 (struct tar_sparse_file *file) xheader_store ("GNU.sparse.realsize", file->stat_info, NULL); file->stat_info->file_name = - xheader_format_name (file->stat_info, "%d/GNUSparseFile.%p/%f", 0); + xheader_format_name (file->stat_info, "%d/GNUSparseFile.0/%f", 0); /* Make sure the created header name is shorter than NAME_FIELD_SIZE: */ if (strlen (file->stat_info->file_name) > NAME_FIELD_SIZE) file->stat_info->file_name[NAME_FIELD_SIZE] = 0; -- 2.56.0