Re: New gold plugin interface for getting --wrap symbols

["Sriraman Tallam via binutils" <binutils at sourceware dot org>]

On Mon, Nov 27, 2017 at 10:31 PM, Cary Coutant <ccoutant@gmail.com> wrote:
>>>      LLVM ThinLTO needs a gold plugin API to get the list of symbols that
>>> are wrapped using the --wrap option to avoid garbage collection of some of
>>> the associated functions like __wrap_symbol and __real_symbol.
>>>
>>>      This patch adds an interface, get_wrap_symbols, to get the count and
>>> the list of symbols that are wrapped.
>
> There's a difference between the list of --wrap options passed to the
> linker (which is what this API returns), and a list of which symbols
> actually got wrapped. How is this useful compared to simply
> pattern-matching for symbols whose name begins with "__wrap" and
> "__real" (which will give you the symbols that were actually wrapped)?
>
> Assuming this is what you want...
>
> +  std::vector<const char *> wrapped_symbols;
> +  uint64_t total = 0;
> +
> +  for (options::String_set::const_iterator
> +       it = parameters->options().wrap_begin();
> +       it != parameters->options().wrap_end(); ++it) {
> +    total++;
> +    wrapped_symbols.push_back(it->c_str());
> +  }
>
> total is redundant -- just use wrapped_symbols.size().
>
> Furthermore, if you add an extra member function to DEFINE_set that
> exposes the String_set::size() method, e.g.:
>
>   options::String_set::size_type
>   varname__##_size() const
>   { return this->varname__##_.value.size(); }
>
> ... you could avoid copying to and from the intermediate vector.
>
> (I *think* all of the various alternative implementations we might use
> for Unordered_set provide a constant-time size() method.)

I have attached the patch with those changes.

 * plugin.cc (get_wrap_symbols): New plugin interface.
(load): Add get_wrap_symbols to transfer vector.
* plugin-api.h (ld_plugin_get_wrap_symbols): New plugin interface.
* options.h (options::String_set::size_type): New macro function.
* testsuite/plugin_test.c (onload): Call and check get_wrap_symbols
interface.
* testsuite/plugin_test_wrap_symbols.sh: New test script.
* testsuite/plugin_test_wrap_symbols_1.cc: New file.
* testsuite/plugin_test_wrap_symbols_2.cc: New file.
* testsuite/Makefile.am (plugin_test_wrap_symbols): New test.
* testsuite/Makefile.in: Regenerate.




Thanks
Sri

>
> -cary

Attachment: plugin_wrap_symbol_patch.txt
Description: Text document