Using std types and functions within GCC

Using std types and functions within GCC

[Pierrick Philippe]

[-- Attachment #1: Type: text/plain, Size: 300 bytes --]

Hi all,

I was wondering, is there any conventions or guidelines regarding the
usage of types and/or functions coming from the C++ std library within
the compiler?

To explicit a bit more, I am working on modification on the analyzer and
might need to use a pair.

Thank you for your time,

Pierrick

Re: Using std types and functions within GCC

[Jonathan Wakely]

On Thu, 14 Mar 2024 at 12:54, Pierrick Philippe
<pierrick.philippe@irisa.fr> wrote:
>
> Hi all,
>
> I was wondering, is there any conventions or guidelines regarding the
> usage of types and/or functions coming from the C++ std library within
> the compiler?

The relevant header needs to be included from the gcc/system.h header.
Look in there for INCLUDE_STRING, INCLUDE_VECTOR etc. and how those
macros are used in other sources.

> To explicit a bit more, I am working on modification on the analyzer and
> might need to use a pair.

A grep of the source shows that <utility> is already included in
gcc/system.h and std::pair is already used in several places.

Re: Using std types and functions within GCC

[David Malcolm]

On Thu, 2024-03-14 at 13:28 +0000, Jonathan Wakely via Gcc wrote:
> On Thu, 14 Mar 2024 at 12:54, Pierrick Philippe
> <pierrick.philippe@irisa.fr> wrote:
> > 
> > Hi all,

Hi Pierrick!  It was good to meet you at FOSDEM.

> > 
> > I was wondering, is there any conventions or guidelines regarding
> > the
> > usage of types and/or functions coming from the C++ std library
> > within
> > the compiler?
> 
> The relevant header needs to be included from the gcc/system.h
> header.
> Look in there for INCLUDE_STRING, INCLUDE_VECTOR etc. and how those
> macros are used in other sources.
> 
> > To explicit a bit more, I am working on modification on the
> > analyzer and
> > might need to use a pair.
> 
> A grep of the source shows that <utility> is already included in
> gcc/system.h and std::pair is already used in several places.

Thanks Jonathan.

A couple of other things to note:

- bear in mind that we need to be somewhat conservative in our usage of
C++ internally: our code needs to be C++11, compilable by GCC 4.8.3,
and parsable by gengtype and by xgettext.  For example, there's at
least one place where I'd have used std::optional, but that's C++14 and
so unavailable.

- some parts of our code manage memory using our custom garbage
collector (via GTY and gengtype), and other parts use C++11 move
semantics.  I suspect that these two approaches to memory management
aren't especially compatible with each other.  For example, our vec<T>
class works with the GC but not (I think) with move, whereas
std::vector works with C++11.  We make the simplifying assumption
within the analyzer that the garbage collector will never run within
the analysis pass, and the analyzer makes use of move semantics, ctors,
dtors, etc.

Feel free to use std::pair in the analyzer.

Hope this is helpful
Dave

Re: Using std types and functions within GCC

[Jonathan Wakely]

On Thu, 14 Mar 2024 at 14:49, David Malcolm <dmalcolm@redhat.com> wrote:
>
> On Thu, 2024-03-14 at 13:28 +0000, Jonathan Wakely via Gcc wrote:
> > On Thu, 14 Mar 2024 at 12:54, Pierrick Philippe
> > <pierrick.philippe@irisa.fr> wrote:
> > >
> > > Hi all,
>
> Hi Pierrick!  It was good to meet you at FOSDEM.
>
> > >
> > > I was wondering, is there any conventions or guidelines regarding
> > > the
> > > usage of types and/or functions coming from the C++ std library
> > > within
> > > the compiler?
> >
> > The relevant header needs to be included from the gcc/system.h
> > header.
> > Look in there for INCLUDE_STRING, INCLUDE_VECTOR etc. and how those
> > macros are used in other sources.
> >
> > > To explicit a bit more, I am working on modification on the
> > > analyzer and
> > > might need to use a pair.
> >
> > A grep of the source shows that <utility> is already included in
> > gcc/system.h and std::pair is already used in several places.
>
> Thanks Jonathan.
>
> A couple of other things to note:
>
> - bear in mind that we need to be somewhat conservative in our usage of
> C++ internally: our code needs to be C++11, compilable by GCC 4.8.3,
> and parsable by gengtype and by xgettext.  For example, there's at
> least one place where I'd have used std::optional, but that's C++14 and
> so unavailable.

C++17, so even more unavailable!

> - some parts of our code manage memory using our custom garbage
> collector (via GTY and gengtype), and other parts use C++11 move
> semantics.  I suspect that these two approaches to memory management
> aren't especially compatible with each other.  For example, our vec<T>
> class works with the GC but not (I think) with move, whereas
> std::vector works with C++11.  We make the simplifying assumption
> within the analyzer that the garbage collector will never run within
> the analysis pass, and the analyzer makes use of move semantics, ctors,
> dtors, etc.
>
> Feel free to use std::pair in the analyzer.
>
> Hope this is helpful
> Dave
>

Re: Using std types and functions within GCC

[Tom Tromey]

>>>>> "David" == David Malcolm via Gcc <gcc@gcc.gnu.org> writes:

David> For example, there's at
David> least one place where I'd have used std::optional, but that's C++14 and
David> so unavailable.

FWIW, gdb had its own gdb::optional (which was really just a
stripped-down copy of the one from libstdc++) to fill exactly this need,
at least until we moved to C++17 this year.  If you need it you could
easily lift it from the gdb repository.

Tom

Re: Using std types and functions within GCC

[dkm]

March 15, 2024 at 2:00 PM, "Tom Tromey" <tom@tromey.com> wrote:
 
> > 
> > "David" == David Malcolm via Gcc <gcc@gcc.gnu.org> writes:
> > 
> 
> David> For example, there's at
> David> least one place where I'd have used std::optional, but that's C++14 and
> David> so unavailable.
> 
> FWIW, gdb had its own gdb::optional (which was really just a
> stripped-down copy of the one from libstdc++) to fill exactly this need,
> at least until we moved to C++17 this year. If you need it you could
> easily lift it from the gdb repository.
> 

Hi,

In the Rust frontend, we are using a single header implementation from https://github.com/TartanLlama/optional, until we can use something from libstdc++.

Marc