On Fri, Sep 27, 2019 at 03:09:30AM +0200, SZEDER Gábor wrote: > On Wed, Sep 25, 2019 at 01:39:19PM -0700, Denton Liu wrote: > > Hi Elijah, > > > > I ran into a segfault on MacOS. I managed to bisect it down to > > 404ebceda0 (dir: also check directories for matching pathspecs, > > 2019-09-17), which should be the patch in the parent thread. The test > > case below works fine without this patch applied but segfaults once it > > is applied. > > > > #!/bin/sh > > > > git worktree add testdir > > git -C testdir checkout master > > git -C testdir fetch https://github.com/git/git.git todo > > bin-wrappers/git -C testdir checkout FETCH_HEAD # segfault here > > > > Note that the worktree part isn't necessary to reproduce the problem but > > I didn't want my files to be constantly refreshed, triggering a rebuild > > each time. > > > > I also managed to get this backtrace from running lldb at the segfault > > but it is based on the latest "jch" commit, 1cc52d20df (Merge branch > > 'jt/merge-recursive-symlink-is-not-a-dir-in-way' into jch, 2019-09-20). > > > > * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x8) > > * frame #0: 0x00000001000f63a0 git`do_match_pathspec(istate=0x0000000100299940, ps=0x000000010200aa80, name="Gitweb/static/js/lib/", namelen=21, prefix=0, seen=0x0000000000000000, flags=0) at dir.c:420:2 [opt] > > frame #1: 0x00000001000f632c git`match_pathspec(istate=0x0000000100299940, ps=0x0000000000000000, name="Gitweb/static/js/lib/", namelen=21, prefix=0, seen=0x0000000000000000, is_dir=0) at dir.c:490:13 [opt] > > frame #2: 0x00000001000f8315 git`read_directory_recursive(dir=0x00007ffeefbfe278, istate=0x0000000100299940, base=<unavailable>, baselen=17, untracked=<unavailable>, check_only=0, stop_at_first_file=0, pathspec=0x0000000000000000) at dir.c:1990:9 [opt] > > frame #3: 0x00000001000f82e9 git`read_directory_recursive(dir=0x00007ffeefbfe278, istate=0x0000000100299940, base=<unavailable>, baselen=14, untracked=<unavailable>, check_only=0, stop_at_first_file=0, pathspec=0x0000000000000000) at dir.c:1984:5 [opt] > > frame #4: 0x00000001000f82e9 git`read_directory_recursive(dir=0x00007ffeefbfe278, istate=0x0000000100299940, base=<unavailable>, baselen=7, untracked=<unavailable>, check_only=0, stop_at_first_file=0, pathspec=0x0000000000000000) at dir.c:1984:5 [opt] > > frame #5: 0x00000001000f60d1 git`read_directory(dir=0x00007ffeefbfe278, istate=0x0000000100299940, path="Gitweb/", len=7, pathspec=0x0000000000000000) at dir.c:2298:3 [opt] > > frame #6: 0x00000001001bded1 git`verify_clean_subdirectory(ce=<unavailable>, o=0x00007ffeefbfe8c0) at unpack-trees.c:1846:6 [opt] > > frame #7: 0x00000001001bdc1d git`check_ok_to_remove(name="Gitweb", len=6, dtype=4, ce=0x0000000103e70de0, st=0x00007ffeefbfe438, error_type=ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o=0x00007ffeefbfe8c0) at unpack-trees.c:1901:7 [opt] > > That 'name="Gitweb" parameter caught my eye. origin/todo contains a > 'Gitweb' file, with upper case 'G', while master contains a 'gitweb' > directory, with lower case 'g'. > > Could it be that case (in)sensitivity plays a crucial rule in > triggering the segfault? FWIW I could reproduce it following Denton's > description on Travis CI's macOS VM with the debug shell access, and > it uses case insensitive file system. Indeed, with 404ebceda0 the test below segfaults on case insensitive fs, but not on a case sensitive one. diff --git a/t/t0050-filesystem.sh b/t/t0050-filesystem.sh index 192c94eccd..5b405c97d7 100755 --- a/t/t0050-filesystem.sh +++ b/t/t0050-filesystem.sh @@ -131,4 +131,27 @@ $test_unicode 'merge (silent unicode normalization)' ' git merge topic ' +test_expect_success CASE_INSENSITIVE_FS "Denton's segfault" ' + git init repo && + ( + cd repo && + + echo foo >Gitweb && + git add Gitweb && + git commit -m "add Gitweb" && + + git checkout --orphan todo && + git reset --hard && + # the subdir is crucial, without it there is no segfault + mkdir -p gitweb/subdir && + echo bar >gitweb/subdir/file && + # it is not strictly necessary to add and commit the + # gitweb directory, its presence is sufficient + git add gitweb && + git commit -m "add gitweb/subdir/file" && + + git checkout master + ) +' + test_done The end of its trace: ++git checkout master ./test-lib.sh: line 910: 11220 Segmentation fault: 11 git checkout master error: last command exited with $?=139 Case insensitivity is important because check_ok_to_remove() is invoked from verify_absent_1(), which looks like this: if (...) .... else if (...) .... else if (lstat(ce->name, &st)) // That lstat() checked whether 'Gitweb' is absent. On a case // sensitive fs it's absent, so it returns. On a case // insensitive fs it finds 'master's 'gitweb' directory, so it // goes on to the else below, and eventually segfaults. return; else check_ok_to_remove() Good night :)
