Re: [BUG] Git 2.38.0-rc1 t1800 message text comparison

From: René Scharfe <l.s.r@web.de>
Date: Jun 4, 2023, 20:55 UTC
Message-ID: <28d808e4-77b4-d91e-8a86-c21287019b56@web.de>
In-Reply-To: <f5519f93-bca7-ecbc-9da3-b25ce8aef618@web.de>

Am 04.06.23 um 14:13 schrieb René Scharfe:

Show 24 quoted lines

> Am 22.05.23 um 23:13 schrieb rsbecker@nexbridge.com:
>> The following is a potential fix:
>>
>> diff --git a/run-command.c b/run-command.c
>> index 60c9419866..b76e117d35 100644
>> --- a/run-command.c
>> +++ b/run-command.c
>> @@ -846,7 +846,7 @@ int start_command(struct child_process *cmd)
>>                         execve(argv.v[0], (char *const *) argv.v,
>>                                (char *const *) childenv);
>>
>> -               if (errno == ENOENT) {
>> +               if (errno == ENOENT || errno == EACCES) {
>>                         if (cmd->silent_exec_failure)
>>                                 child_die(CHILD_ERR_SILENT);
>>                         child_die(CHILD_ERR_ENOENT);
>>
>> This does pass and should cover all POSIX interpretations.
>
> That would misreport execution failures due to missing permissions
> (think e.g. "chmod 0 file") as "No such file or directory".  So this
> should be only done if really needed, perhaps guarded by an access(2)
> check for verifying that EACCES is bogus, and only on affected
> platforms.

Actually the difference is a bit more subtle. With that patch and silent_exec_failure on, missing permissions wouldn't be reported anymore, and with it off the eventual message command would change from:

                error_errno("cannot exec '%s'", cmd->args.v[0]);

to:

                error_errno("cannot run %s", cmd->args.v[0]);

So the actual errno-based message would be the same, unless its suppressed.

What's the significance of "run" and "exec" here? Why do we have both variants? Is it to tell apart errors of the actual execve(2) call from those in code leading up to it (e.g. when searching the executable in $PATH)? But at this point we are after the call, so why is ENOENT from execve(2) a "run" thing, not an "exec" thing?

René