Re: [PATCH v4] pager: fix crash when pager program doesn't exist

> When prepare_cmd() fails for, e.g., pager process setup,
> child_process_clear() frees the memory in pager_process.args, but .argv
> was pointed to pager_process.args.v earlier in start_command(), so it's
> now a dangling pointer.
>
> setup_pager() is then called a second time, from cmd_log_init_finish()
> in this case, and any further operations using its .argv, e.g. strvec_*,
> will use the dangling pointer and eventually crash. According to trivial
> tests, setup_pager() is not called twice if the first call is
> successful.
>
> This patch makes sure that pager_process is properly initialized on
> setup_pager(). Drop CHILD_PROCESS_INIT from its declaration since it's
> no longer really necessary.
>
> Add a test to catch possible regressions.
>
> Reproducer:
> $ git config pager.show INVALID_PAGER
> $ git show $VALID_COMMIT
> error: cannot run INVALID_PAGER: No such file or directory
> [1]    3619 segmentation fault (core dumped)  git show $VALID_COMMIT
>
> Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
> ---
> Changes to v3:
>  - change test description, as per Eric's suggestion
>  - drop CHILD_PROCESS_INIT, as per Jeff's suggestion