Re: Weird problems with C extension and bytea as input type

On Wed, Mar 23, 2011 at 14:08, Merlin Moncure <mmoncure@gmail.com> wrote:
> On Wed, Mar 23, 2011 at 9:04 AM, dennis jenkins
> <dennis.jenkins.75@gmail.com> wrote:
>> On Wed, Mar 23, 2011 at 5:08 AM, Adrian Schreyer <ams214@cam.ac.uk> wrote:
>>>
>>> you are right, it returns a char *.
>>>
>>> The prototype:
>>>
>>> char *function(bytea *b);
>>>
>>> The actual C++ function looks roughly like this
>>>
>>> extern "C"
>>> char *function(bytea *b)
>>> {
>>>   string ism;
>>>   [...]
>>>   return ism.c_str();
>>> }
>>>
>>
>>
>> Don't do that.  You are returning a pointer to an unallocated buffer
>> (previously held by a local variable).  c_str() is just a const
>> pointer to a buffer held inside "ism".  When ism goes out of scope,
>> that buffer if freed.
>>
>> Either return "std::string", or strdup() the string and have the
>> caller free that.  (but use the postgresql alloc pool function to
>> handle the strdup.  I don't recall that function's name off the top of
>> my head).
>
> that would be pstrdup, and it's the way to go (you don't have to
> pfree).  who says C doesn't have garbage collection?
>
> merlin
>
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I am using pstrdup and it works now as expected. Thank you all for your help,

Adrian