archive_entry_pathname returns a nullptr

[hgrossauer]

Basic Information
Version of libarchive: 3.6.2
How you obtained it: build from source
Operating system and version: CentOS-7
What compiler and/or IDE you are using (include version): gcc (GCC) 11.1.1 20210428 (Red Hat 11.1.1-1)

Description of the problem you are seeing:
What did you do?
r = archive_read_next_header(m_ina, &m_entry);
if(r != ARCHIVE_OK){ /* error handling and bail out */ }
std::string filename = archive_entry_pathname(m_entry);

What did you expect to happen?
Get a valid pointer.

What actually happened?
SIGSEGV because archive_entry_pathname returns a nullptr

Some gdb output:

(gdb) p r
$8 = 0
(gdb) p *m_ina
$7 = {magic = 14594245, state = 4, vtable = 0x87e2a0 <archive_read_vtable>, archive_format = 327680, archive_format_name = 0x7fea780029b0 "ZIP 2.0 (uncompressed)", file_count = 1,
archive_error_number = 0, error = 0x0, error_string = {s = 0x7fea78101700 "Xar not supported on this platform", length = 0, buffer_length = 64}, current_code = 0x7fea78000e90 "ANSI_X3.4-1968",
current_codepage = 4294967295, current_oemcp = 4294967295, sconv = 0x7fea78002940, read_data_block = 0x0, read_data_offset = 0, read_data_output_offset = 0, read_data_remaining = 0,
read_data_is_posix_read = 0 '\000', read_data_requested = 0}
(gdb) p *m_entry
$9 = {archive = 0x0, stat = 0x0, stat_valid = 0, ae_stat = {aest_atime = 0, aest_atime_nsec = 0, aest_ctime = 0, aest_ctime_nsec = 0, aest_mtime = 1696927792, aest_mtime_nsec = 0, aest_birthtime = 0,
aest_birthtime_nsec = 0, aest_gid = 0, aest_ino = 0, aest_nlink = 0, aest_size = 0, aest_uid = 0, aest_dev_is_broken_down = 0, aest_dev = 0, aest_devmajor = 0, aest_devminor = 0,
aest_rdev_is_broken_down = 0, aest_rdev = 0, aest_rdevmajor = 0, aest_rdevminor = 0}, ae_set = 92, ae_fflags_text = {aes_mbs = {s = 0x0, length = 0, buffer_length = 0}, aes_utf8 = {s = 0x0,
length = 0, buffer_length = 0}, aes_wcs = {s = 0x0, length = 0, buffer_length = 0}, aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_fflags_set = 0,
ae_fflags_clear = 0, ae_gname = {aes_mbs = {s = 0x0, length = 0, buffer_length = 0}, aes_utf8 = {s = 0x0, length = 0, buffer_length = 0}, aes_wcs = {s = 0x0, length = 0, buffer_length = 0},
aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_hardlink = {aes_mbs = {s = 0x0, length = 0, buffer_length = 0}, aes_utf8 = {s = 0x0, length = 0, buffer_length = 0},
aes_wcs = {s = 0x0, length = 0, buffer_length = 0}, aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_pathname = {aes_mbs = {
s = 0x7fea78104380 "GEM??_eSyStep_OC_IODD_V1.0.0.1/", length = 31, buffer_length = 252}, aes_utf8 = {s = 0x0, length = 0, buffer_length = 0}, aes_wcs = {s = 0x0, length = 0, buffer_length = 0},
aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_symlink = {aes_mbs = {s = 0x0, length = 0, buffer_length = 0}, aes_utf8 = {s = 0x0, length = 0, buffer_length = 0},
aes_wcs = {s = 0x0, length = 0, buffer_length = 0}, aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_uname = {aes_mbs = {s = 0x0, length = 0, buffer_length = 0},
aes_utf8 = {s = 0x0, length = 0, buffer_length = 0}, aes_wcs = {s = 0x0, length = 0, buffer_length = 0}, aes_mbs_in_locale = {s = 0x0, length = 0, buffer_length = 0}, aes_set = 0}, ae_sourcepath = {
aes_mbs = {s = 0x0, length = 0, buffer_length = 0}, aes_utf8 = {s = 0x0, length = 0, buffer_length = 0}, aes_wcs = {s = 0x0, length = 0, buffer_length = 0}, aes_mbs_in_locale = {s = 0x0, length = 0,
buffer_length = 0}, aes_set = 0}, encryption = 0 '\000', mac_metadata = 0x0, mac_metadata_size = 0, digest = {md5 = '\000' <repeats 15 times>, rmd160 = '\000' <repeats 19 times>,
sha1 = '\000' <repeats 19 times>, sha256 = '\000' <repeats 31 times>, sha384 = '\000' <repeats 47 times>, sha512 = '\000' <repeats 63 times>}, acl = {mode = 16893, acl_head = 0x0, acl_p = 0x0,
acl_state = 0, acl_text_w = 0x0, acl_text = 0x0, acl_types = 0}, xattr_head = 0x0, xattr_p = 0x0, sparse_head = 0x0, sparse_tail = 0x0, sparse_p = 0x0, strmode = '\000' <repeats 11 times>,
ae_symlink_type = 0}

[kientzle]

The m_entry structure here does not hold a valid filename because ae_pathname.aes_set == 0. So it makes sense that you would get NULL when querying the pathname. Some archive formats can have entries that lack filenames; can you provide details of the particular archive that was being read?

[hgrossauer]

In the meantime I have “fixed” my code to expect and handle this behavior. Personally I would prefer returning a pointer to an empty string instead of a nullptr. Or maybe the behavior (no matter what) should be documented, I haven’t found anything regarding this.

[kientzle]

Pull Requests to update the documentation are greatly appreciated.