Re: Git Stash brake splitIndex

[Christian Couder <christian.couder@gmail.com>]

Hi,

On Tue, Apr 28, 2020 at 3:21 PM Son Luong Ngoc <sluongng@gmail.com> wrote:

> I am on git version 2.26.2.526.g744177e7f7 (latest next)
> When you do a git stash while using splitIndex, it seems like the index will get corrupted
>
> Using configs:
> core.splitindex=true
> splitindex.maxpercentchange=50
> splitindex.sharedindexexpire=now
>
> Reproduce steps:
>
> mkdir repo
> cd repo && git init
> echo a > a
> commit -a -m 'add a'

It looks like it should be `git commit -a -m 'add a'`

When I try to reproduce the steps using git version 2.26.2.526.g744177e7f7:

mkdir repo
cd repo && git init
git config core.splitindex true
git config splitindex.maxpercentchange 50
git config splitindex.sharedindexexpire now
echo a > a
git commit -a -m 'add a'

I get a segfault then:

Program received signal SIGSEGV, Segmentation fault.
0x00005555556ccf89 in ewah_each_bit (self=0x0, callback=0x5555557af648
<replace_entry>, payload=0x555555b47480 <the_index>)
    at ewah/ewah_bitmap.c:252
252             while (pointer < self->buffer_size) {
(gdb) bt
#0  0x00005555556ccf89 in ewah_each_bit (self=0x0,
callback=0x5555557af648 <replace_entry>, payload=0x555555b47480
<the_index>)
    at ewah/ewah_bitmap.c:252
#1  0x00005555557af90c in merge_base_index (istate=0x555555b47480
<the_index>) at split-index.c:162
#2  0x0000555555748b9f in read_index_from (istate=0x555555b47480
<the_index>, path=0x555555b4cd80 ".git/index",
    gitdir=0x555555b4ac20 ".git") at read-cache.c:2335
#3  0x000055555576faf3 in repo_read_index (repo=0x555555b33f20
<the_repo>) at repository.c:271
#4  0x000055555559b91b in prepare_to_commit (index_file=0x555555b4d760
"/tmp/git/repo/.git/index.lock", prefix=0x0,
    current_head=0x0, s=0x555555b04420 <s>,
author_ident=0x7fffffffd810) at builtin/commit.c:927
#5  0x000055555559d6a4 in cmd_commit (argc=0, argv=0x7fffffffdcf0,
prefix=0x0) at builtin/commit.c:1595
#6  0x0000555555570fda in run_builtin (p=0x555555af1218
<commands+504>, argc=4, argv=0x7fffffffdcf0) at git.c:447
#7  0x000055555557134b in handle_builtin (argc=4, argv=0x7fffffffdcf0)
at git.c:672
#8  0x0000555555571610 in run_argv (argcp=0x7fffffffdb9c,
argv=0x7fffffffdb90) at git.c:739
#9  0x0000555555571aba in cmd_main (argc=4, argv=0x7fffffffdcf0) at git.c:870
#10 0x0000555555641bc4 in main (argc=5, argv=0x7fffffffdce8) at common-main.c:52

It looks like merge_base_index() in split-index.c is calling
ewah_each_bit(si->replace_bitmap, replace_entry, istate) when
si->replace_bitmap is NULL.