Re: GSoC: Getting started

[David Malcolm <dmalcolm@redhat.com>]

On Wed, 2022-06-01 at 14:50 -0400, David Malcolm wrote:
> On Wed, 2022-06-01 at 23:22 +0530, Mir Immad wrote:
> > HI everyone,
> > 
> > I'm Immad Mir -- one of the GSoC students this year. I'll be working
> > on
> > adding static analysis support for POSIX file description APIs this
> > summer.
> 
> Welcome Immad - I'm looking forward to helping you on this project.
> 
> For reference, I think you posted an initial prototype of this work
> earlier this year here:
>   https://gcc.gnu.org/pipermail/gcc/2022-January/238192.html
>   https://gcc.gnu.org/pipermail/gcc/2022-February/238215.html
> 
> > 
> > The plan is to let the static analyzer know about the FD APIs through
> > the
> > use of function attributes, although initially we might hardcode the
> > logic
> > to get started working. I'm looking for the suggestions on this from
> > the
> > people who have experience working with file-descriptors.
> 
> We talked about this off-list; I think next steps could be:
> 
> (1) get your initial prototype working again, hardcoding the names of
> the functions for simplicity at first
> 
> (2) find a list of system calls (e.g. those implemented on Linux), and
> see which ones relate to file descriptors e.g. acquiring them, using
> them, releasing them, and duplicating them.  Look for patterns of usage
> that could be expressed using function attributes.  Probably ignore
> "ioctl" for now.
> 
> (3) probably talk to glibc's developers about this, since glibc
> provides headers that wrap system calls, which would want to use the
> attributes if we provide them
> 
> (4) implement the attributes, so that the analyzer doesn't have
> hardcoded function names, and can instead rely on function attributes.
> GCC's attributes are implemented in gcc/c-family/c-attribs.cc; see the
> big c_common_attribute_table array, which associates the string names
> of the attrbutes with properties, including a handler callback.  These
> either set flags of a decl, or the attribute itself is appended to a
> singly-linked list on that decl (for those things that don't directly
> relate to fields of a decl).
> 
> I believe Siddhesh Poyarekar has been looking at attributes from the
> glibc side of things, so I'm CCing him in case he has input on this.
> 
> I'm wondering if other people on this list have ideas for projects that
> make heavy use of syscalls/file-descriptors that would benefit from
> having this analyzer feature.  Maybe systemd?
> 
> Welcome again; hope this makes sense and is helpful
> Dave

I've gone ahead and filed an RFE bug in our bugzilla to help track this
work:
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106003

Immad: you should probably assign that bug to yourself.  Do you have an
account yet for bugzilla?  See:
  https://gcc.gnu.org/gitwrite.html#authenticated
for info on how to get an account on sourceware.org/gcc.gnu.org

I can be your sponsor.

Once you have that, I think you automatically get a
USERNAME@gcc.gnu.org account that you can use to login to the GCC
bugzilla.


Dave