Re: [PATCH] Fix calling gcore when gdb is not in $PATH.

[Luis Machado <lgustavo@codesourcery.com>]

On 10/11/2013 03:10 PM, Jan Kratochvil wrote:
> On Fri, 11 Oct 2013 19:53:12 +0200, Luis Machado wrote:
>> On 10/11/2013 01:56 PM, Jan Kratochvil wrote:
>>> On Fri, 11 Oct 2013 18:46:15 +0200, Luis Machado wrote:
>>>> --- a/gdb/gcore.in
>>>> +++ b/gdb/gcore.in
>>>> @@ -49,9 +49,26 @@ rc=0
>>>>   # Loop through pids
>>>>   for pid in $*
>>>>   do
>>>> +# Attempt to fetch the absolute path to the gcore script that was
>>>> +# called.
>>>> +binary_path=`dirname "$0"`
>>>> +
>>>> +	if test "x$binary_path" = x. ; then
>>>> +	  # We got "." back as a path.  This means the user executed
>>>> +	  # the gcore script locally (i.e. ./gcore) or called the
>>>> +	  # script via a shell interpreter (i.e. sh gcore).  We use
>>>> +	  # the "which" command to locate the real path of the gcore
>>>> +	  # script, disambiguating this situation.
>>>> +	  binary_path_from_env=`which "$0"`
>>>> +	  binary_path=`dirname $binary_path_from_env`
>>>
>>> In generally OK, just still ... is there some reason for this 'which' search?
>>> Moreover if one really runs ./gcore then it should IMO take ./gdb (and not some
>>> other gdb), if we should really pick GDB from the directory of gcore.
>>
>> Yes. The reason is to pick the gdb binary from the directory that
>> contains the gcore script the user invoked.
>>
>> If the user issued "sh gcore" and /usr/bin/gcore was picked (based
>> on $PATH), then we should use /usr/bin/gdb.
>>
>> Now, if the user issued "./gcore", ./gdb will be picked up, and so on.
>>
>> Does it make sense?
>
> Great we agree.  But your code does pick /usr/bin/gdb for ./gcore, doesn't it?
> Which is why I proposed the change I proposed.

Hmmm... unless there is some discrepancy between shell interpreters, 
mine (bash) does the following:

Invocation: ./gcore
dirname ./gcore -> .

So we go inside the if block and locate the real binary that is being 
called based on $PATH.

which ./gcore -> ./gcore

So we pick the dirname of ./gcore (which is ".") and add a slash to it, 
resulting in ./gdb.

Do you see something different or a corner case?

Luis