From: Phillip Wood Date: Tue, 29 Apr 2025 09:22:14 GMT Subject: Re: [BUG] rebase: can write reflog with uninit. `action` string Message-ID: In-Reply-To: <20250428194048.149348-1-code@khaugsbakk.name> Hi Kristoffer On 28/04/2025 20:40, Kristoffer Haugsbakk wrote: > From: code@khaugsbakk.name > > We did `git rebase --rebase-merges` on a branch with merge commits. Including > back merges. The reflog after that showed some weird symbols for > certain merge commits (only merges): > > e9c962f2ea0 HEAD@{8}: �: Merged in (pull request #4441) Thanks for reporting this. I'm afraid I'm rather confused. In run_git_commit() we set GIT_REFLOG_ACTION with strvec_pushf(&cmd.env, GIT_REFLOG_ACTION "=%s", ctx->reflog_message); ctx is allocated with calloc() so ctx->reflog_message is initially NULL. At the start of pick_commits() we store the result of sequencer_reflog_action() in ctx->reflog_message. That function returns a heap allocation that is not freed until we call replay_opts_release() at the end of the rebase. If we're doing a normal pick rather than a merge we store the result of reflog_message() in ctx->reflog_message. That function returns a string stored in a static strbuf. So when we call do_merge() from pick_commits() ctx->reflog_message should point to a valid string though that string will not hold the correct reflog message for the merge because do_merge() does not call reflog_message(). > This is the backtrace when I get the apparently uninit. string: > > ``` > #0 run_git_commit (defmsg=0x555555babe70 "/MERGE_MSG", opts=0x7fffffffc070, flags=0) at sequencer.c:1158 Thanks for the backtrace. It would be useful to know what's stored in opts->ctx->reflog_message at this point if it's not too much trouble please can you run "print *opts" and "print *opts->ctx" here. Thanks Phillip > #1 0x00005555558740d9 in do_merge (r=0x555555a67020 , commit=0x555555b75cb0, > arg=0x555555b2164d " # Merged in { (pull request #4464)\nlabel branch-point-9\npick 4026b5ced849724bd3857283b6ad50c8609b6d33 only sh"..., arg_len=125, flags=0, check_todo=0x7fffffffb1e0, opts=0x7fffffffc070) at sequencer.c:4380 > #2 0x0000555555876629 in pick_commits (r=0x555555a67020 , todo_list=0x7fffffffbf50, opts=0x7fffffffc070) at sequencer.c:5048 > #3 0x0000555555877eeb in sequencer_continue (r=0x555555a67020 , opts=0x7fffffffc070) at sequencer.c:5480 > #4 0x000055555563a491 in run_sequencer_rebase (opts=0x7fffffffc330) at builtin/rebase.c:369 > #5 0x000055555563bc74 in run_specific_rebase (opts=0x7fffffffc330) at builtin/rebase.c:746 > #6 0x000055555563fe2a in cmd_rebase (argc=0, argv=0x555555a73890, prefix=0x0, repo=0x555555a67020 ) at builtin/rebase.c:1878 > #7 0x0000555555574c0d in run_builtin (p=0x555555a34908 , argc=2, argv=0x555555a73890, repo=0x555555a67020 ) at git.c:480 > #8 0x00005555555750ca in handle_builtin (args=0x7fffffffd8a0) at git.c:743 > #9 0x000055555557538c in run_argv (args=0x7fffffffd8a0) at git.c:810 > #10 0x00005555555759e2 in cmd_main (argc=2, argv=0x7fffffffda30) at git.c:950 > #11 0x000055555569b0c3 in main (argc=5, argv=0x7fffffffda18) at common-main.c:9 > ``` > > § No reproduction script > > I was unable to reproduce with a simple repo. setup. I tried: > > 1. Creating a side branch which had a merge > 2. The side branch conflicted with the other branch > 3. Rebased with `--rebase-merges` > > ----- > > Normal bugreport questionaire follows. > > ----- > > Thank you for filling out a Git bug report! > Please answer the following questions to help us understand your issue. > > What did you do before the bug happened? (Steps to reproduce your issue) > > `git rebase --rebase-merges` on a branch with merge commits. Including > back merges. > > What did you expect to happen? (Expected behavior) > > Normal “action” string for the reflog like for example `continue`: > > 3f90f6ab14d (HEAD -> ) HEAD@{1}: rebase (continue): Merged in (pull request #4507) > > What happened instead? (Actual behavior) > > The “action” (or whatever it is) string is arbitrary bytes. Like some > uninit. memory. > > ``` > e9c962f2ea0 HEAD@{8}: �: Merged in (pull request #4441) > ``` > > What's different between what you expected and what actually happened? > > Apparently uninit. string. > > Anything else you want to add: > > Please review the rest of the bug report below. > You can delete any lines you don't wish to share. > > > [System Info] > git version: > git version 2.49.0.459.gf65182a99e5 > cpu: x86_64 > built from commit: f65182a99e545d2f2bc22e6c1c2da192133b16a3 > sizeof-long: 8 > sizeof-size_t: 8 > shell-path: /bin/sh > libcurl: 7.81.0 > OpenSSL: OpenSSL 3.0.2 15 Mar 2022 > zlib: 1.2.11 > SHA-1: SHA1_DC > SHA-256: SHA256_BLK > uname: Linux 6.8.0-58-generic #60~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar 28 16:09:21 UTC 2 x86_64 > compiler info: gnuc: 11.4 > libc info: glibc: 2.35 > $SHELL (typically, interactive shell): /bin/bash > > > [Enabled Hooks] >