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

On Wed, Mar 23, 2011 at 9:04 AM, dennis jenkins
<dennis(dot)jenkins(dot)75(at)gmail(dot)com> wrote:
> On Wed, Mar 23, 2011 at 5:08 AM, Adrian Schreyer <ams214(at)cam(dot)ac(dot)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