Re: [PATCH] sub-process: print the cmd when a capability is unsupported

From: Christian Couder <christian.couder@gmail.com>
Date: Aug 15, 2017, 19:29 UTC
Message-ID: <CAP8UFD2KBEVwZE8obaDxf+0AyU4zH0+5bWJzzHazFywgWT9QjQ@mail.gmail.com>
In-Reply-To: <836F754B-C78C-4D19-8365-875D96B3F115@gmail.com>

On Tue, Aug 15, 2017 at 9:00 PM, Lars Schneider <larsxschneider@gmail.com> wrote:

Show 48 quoted lines

>
>> On 15 Aug 2017, at 19:36, Christian Couder <christian.couder@gmail.com> wrote:
>>
>> In handshake_capabilities() we use warning() when a capability
>> is not supported, so the exit code of the function is 0 and no
>> further error is shown. This is a problem because the warning
>> message doesn't tell us which subprocess cmd failed.
>>
>> On the contrary if we cannot write a packet from this function,
>> we use error() and then subprocess_start() outputs:
>>
>>    initialization for subprocess '<cmd>' failed
>>
>> so we can know which subprocess cmd failed.
>>
>> Let's improve the warning() message, so that we can know which
>> subprocess cmd failed.
>>
>> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
>> ---
>> sub-process.c | 13 ++++++++-----
>> 1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/sub-process.c b/sub-process.c
>> index 6edb97c1c6..6b133f8dce 100644
>> --- a/sub-process.c
>> +++ b/sub-process.c
>> @@ -158,7 +158,8 @@ static int handshake_version(struct child_process *process,
>>
>> static int handshake_capabilities(struct child_process *process,
>>                                 struct subprocess_capability *capabilities,
>> -                               unsigned int *supported_capabilities)
>> +                               unsigned int *supported_capabilities,
>> +                               const char *cmd)
>> {
>>       int i;
>>       char *line;
>> @@ -184,8 +185,8 @@ static int handshake_capabilities(struct child_process *process,
>>                       if (supported_capabilities)
>>                               *supported_capabilities |= capabilities[i].flag;
>>               } else {
>> -                     warning("external filter requested unsupported filter capability '%s'",
>> -                             p);
>> +                     warning("subprocess '%s' requested unsupported capability '%s'",
>> +                             cmd, p);
>
> Wouldn't it be possible to use "process->argv[0]"?
> Shouldn't that be the same as "cmd"?

Well in sub-process.h there is:

/* Members should not be accessed directly. */
struct subprocess_entry {
    struct hashmap_entry ent; /* must be the first member! */
    const char *cmd;
    struct child_process process;
};

so if cmd is always the same as process->argv[0], maybe there is no need for the cmd member in the first place?