Re: [PATCH v2] gdb: CTF support

[Simon Marchi <simark@simark.ca>]

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.

Simon