[cfe-dev] Adding custom attributes/metadata to functions and globals

[Friedman, Eli via cfe-dev]

On 10/29/2016 11:23 AM, Félix Cloutier via cfe-dev wrote:
> Hello all,
>
> I'm working on a project that parses C headers with the Clang static 
> libraries for binary program analysis purposes. I consume the AST and 
> do not rely on codegen.
>
> I would love to be able to add some additional metadata to functions: 
> specifically, the expected address of the function in the binary 
> program. For instance:
>
> int foo(int bar) __attribute__((address(0xdeadbeef)));
>
> Attributes are especially convenient because they are easy to embed in 
> a macro, which could end up looking like:
>
> int foo(int bar) ADDRESS(0xdeadbeef);
>
> Since this is an open-source project maintained by me only, I would 
> prefer to not fork Clang, and just allow people to build my program 
> with their distributions' stock Clang packages. Sadly, this apparently 
> means that I can't use attributes for this purpose, because the valid 
> attribute list appears to be hard-coded into Clang, and there doesn't 
> seem to be any attribute that I can co-opt for this purpose.
>
> Are there extension points that I can leverage in the Clang static 
> libraries to allow this?

The "annotate" attribute (`void f() __attribute((annotate("asdf"))) {}`) 
takes an arbitrary string, and has no semantic effect.

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project