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

> On 15 Aug 2017, at 21:29, Christian Couder <christian.couder@gmail.com> wrote:
> 
> On Tue, Aug 15, 2017 at 9:00 PM, Lars Schneider
> <larsxschneider@gmail.com> wrote:
>> 
>>> 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?