Re: [PATCH v2] gdb: CTF support

[Wei-min Pan <weimin.pan@oracle.com>]

On 10/3/2019 11:31 AM, Simon Marchi wrote:
> On 2019-10-03 2:21 p.m., Wei-min Pan wrote:
>> Let's use an example (checking omitted):
>>
>> We're replacing:
>>    name = ctf_type_aname_raw (fp, tid);
>>    TYPE_NAME (type) = obstack_strdup (&of->objfile_obstack, name);
>>    free (name);
>>
>> with
>>    gdb::unique_xmalloc_ptr<char> name (ctf_type_aname_raw (fp, tid));
>>    TYPE_NAME (type) = obstack_strdup (&of->objfile_obstack, name.get ());
>>
>> The allocated copy from ctf_type_aname_raw is not freed. Or did I miss something?
>>
>> Weimin
> Yes, the second snippet frees the copy returned by ctf_type_aname_raw.
>
> It might just be that you are not familiar with the concept of std::unique_ptr in C++:
>
>    https://en.cppreference.com/w/cpp/memory/unique_ptr
>
> It's a wrapper around a simple pointer that automatically calls a deleter function
> when it goes out of scope.  gdb::unique_xmalloc_ptr is a specialization of std::unique_ptr
> that uses xfree as the deleter function.
>
> Here's a similar use:
>
>    https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=gdb/fbsd-tdep.c;h=9422e3c1a7e1a65c76b088f42bb5986bd13a089f;hb=HEAD#l1530
>
> `fbsd_core_vnode_path` return a pointer to an allocated C String, which `cwd` wraps.  When
> it goes out of scope, `cwd` automatically calls `xfree` with the pointer.

Oh, thanks for the explanation, reference and example. Will switch to 
using gdb::unique_xmalloc_ptr<> instead.

Weimin
>
> Simon