No description
68006d1732
We bumped into the build error while testing gcc-10 pre-release.
In file included from ../../include/grub/file.h:22,
from ../../grub-core/fs/zfs/zfs.c:34:
../../grub-core/fs/zfs/zfs.c: In function 'zap_leaf_lookup':
../../grub-core/fs/zfs/zfs.c:2263:44: error: array subscript '<unknown>' is outside the bounds of an interior zero-length array 'grub_uint16_t[0]' {aka 'short unsigned int[0]'} [-Werror=zero-length-bounds]
2263 | for (chunk = grub_zfs_to_cpu16 (l->l_hash[LEAF_HASH (blksft, h, l)], endian);
../../include/grub/types.h:241:48: note: in definition of macro 'grub_le_to_cpu16'
241 | # define grub_le_to_cpu16(x) ((grub_uint16_t) (x))
| ^
../../grub-core/fs/zfs/zfs.c:2263:16: note: in expansion of macro 'grub_zfs_to_cpu16'
2263 | for (chunk = grub_zfs_to_cpu16 (l->l_hash[LEAF_HASH (blksft, h, l)], endian);
| ^~~~~~~~~~~~~~~~~
In file included from ../../grub-core/fs/zfs/zfs.c:48:
../../include/grub/zfs/zap_leaf.h:72:16: note: while referencing 'l_hash'
72 | grub_uint16_t l_hash[0];
| ^~~~~~
Here I'd like to quote from the gcc document [1] which seems best to
explain what is going on here.
"Although the size of a zero-length array is zero, an array member of
this kind may increase the size of the enclosing type as a result of
tail padding. The offset of a zero-length array member from the
beginning of the enclosing structure is the same as the offset of an
array with one or more elements of the same type. The alignment of a
zero-length array is the same as the alignment of its elements.
Declaring zero-length arrays in other contexts, including as interior
members of structure objects or as non-member objects, is discouraged.
Accessing elements of zero-length arrays declared in such contexts is
undefined and may be diagnosed."
The l_hash[0] is apparnetly an interior member to the enclosed structure
while l_entries[0] is the trailing member. And the offending code tries
to access members in l_hash[0] array that triggers the diagnose.
Given that the l_entries[0] is used to get proper alignment to access
leaf chunks, we can accomplish the same thing through the ALIGN_UP macro
thus eliminating l_entries[0] from the structure. In this way we can
pacify the warning as l_hash[0] now becomes the last member to the
enclosed structure.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
|
||
|---|---|---|
| asm-tests | ||
| conf | ||
| docs | ||
| grub-core | ||
| include | ||
| po | ||
| tests | ||
| themes/starfield | ||
| unicode | ||
| util | ||
| .gitattributes | ||
| .gitignore | ||
| .travis.yml | ||
| acinclude.m4 | ||
| AUTHORS | ||
| autogen.sh | ||
| bootstrap | ||
| bootstrap.conf | ||
| BUGS | ||
| ChangeLog-2015 | ||
| config.h.in | ||
| configure.ac | ||
| COPYING | ||
| coreboot.cfg | ||
| geninit.sh | ||
| gentpl.py | ||
| INSTALL | ||
| linguas.sh | ||
| Makefile.am | ||
| Makefile.util.def | ||
| NEWS | ||
| README | ||
| THANKS | ||
| TODO | ||
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'