Re: [PATCH v3] c, analyzer: support named constants in analyzer [PR106302]

[Marek Polacek <polacek@redhat.com>]

On Tue, Nov 15, 2022 at 01:35:05PM -0500, David Malcolm wrote:
> On Mon, 2022-11-14 at 15:42 -0500, Marek Polacek wrote:
> > On Fri, Nov 11, 2022 at 10:23:10PM -0500, David Malcolm wrote:
> > > Changes since v1: ported the doc changes from texinfo to sphinx
> > > 
> > > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
> > > 
> > > Are the C frontend parts OK for trunk?  (I can self-approve the
> > > analyzer parts)
> > 
> > Sorry for the delay.
> >  
> > > The patch adds an interface for frontends to call into the analyzer
> > > as
> > > the translation unit finishes.  The analyzer can then call back
> > > into the
> > > frontend to ask about the values of the named constants it cares
> > > about
> > > whilst the frontend's data structures are still around.
> > > 
> > > The patch implements this for the C frontend, which looks up the
> > > names
> > > by looking for named CONST_DECLs (which handles enum values). 
> > > Failing
> > > that, it attempts to look up the values of macros but only the
> > > simplest
> > > cases are supported (a non-traditional macro with a single
> > > CPP_NUMBER
> > > token).  It does this by building a buffer containing the macro
> > > definition and rerunning a lexer on it.
> > > 
> > > The analyzer gracefully handles the cases where named values aren't
> > > found (such as anything more complicated than described above).
> > > 
> > > The patch ports the analyzer to use this mechanism for "O_RDONLY",
> > > "O_WRONLY", and "O_ACCMODE".  I have successfully tested my socket
> > > patch
> > > to also use this for "SOCK_STREAM" and "SOCK_DGRAM", so the
> > > technique
> > > seems to work.
> > 
> > So this works well for code like
> > 
> > enum __socket_type {
> >     SOCK_STREAM = 1,
> > 
> > #define SOCK_STREAM SOCK_STREAM
> > };
> > 
> > ?
> 
> Yes: c_translation_unit::lookup_constant_by_id does the "lookup_name"
> first, and this finds the CONST_DECL, so it doesn't need to look at
> macros for this case.

Ah, nice.
 
> I've added a testcase for this in the v3 patch (gcc.dg/analyzer/named-
> constants-via-enum-and-macro.c)

Thanks.

> Thanks for the review.  Here's a v3 version of the patch.
> 
> Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
> 
> Are the C FE parts OK for trunk?

Ok, thanks.
 

Marek