| Message ID | 20221026204005.1864136-1-dmalcolm@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] Add gcc/make-unique.h | expand |
On 10/26/22 16:40, David Malcolm via Gcc-patches wrote: > Changed in v3: added include of <type_traits> > v2: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/604137.html > v1: https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598189.html > > On Tue, 2022-07-12 at 07:48 +0100, Jonathan Wakely wrote: >> On Tue, 12 Jul 2022, 01:25 David Malcolm, <dmalcolm@redhat.com> >> wrote: >> >>> On Fri, 2022-07-08 at 22:16 +0100, Jonathan Wakely wrote: >>>> On Fri, 8 Jul 2022 at 21:47, David Malcolm via Gcc >>>> <gcc@gcc.gnu.org> >>>> wrote: >>>>> >>>>> std::unique_ptr is C++11, and I'd like to use it in the >>>>> gcc/analyzer >>>>> subdirectory, at least. The following patch eliminates a bunch >>>>> of >>>>> "takes ownership" comments and manual "delete" invocations in >>>>> favor >>>>> of simply using std::unique_ptr. >>>>> >>>>> The problem is that the patch makes use of std::make_unique, >>>>> but >>>>> that >>>>> was added in C++14. >>>>> >>>>> I've heard that it's reasonably easy to reimplement >>>>> std::make_unique, >>>>> but I'm not sure that my C++11 skills are up to it. >>>> >>>> You know we have an implementation of std::make_unique in GCC, >>>> with a >>>> GCC-compatible licence that you can look at, right? :-) >>>> >>>> But it's not really necessary. There are only two reasons to >>>> prefer >>>> make_unique over just allocating an object with new and >>>> constructing >>>> a >>>> unique_ptr from it: >>>> >>>> 1) avoid a "naked" new in your code (some coding styles like >>>> this, >>>> but >>>> it's not really important as long as the 'delete' is managed >>>> automatically by unique_ptr). >>>> >>>> 2) exception-safety when allocating multiple objects as args to a >>>> function, see https://herbsutter.com/gotw/_102/ for details. >>>> Irrelevant for GCC, because we build without exceptions. >>> >>> [moving from gcc to gcc-patches mailing list] >>> >>> Also, I *think* it's a lot less typing, since I can write just: >>> >>> std::make_unique<name_of_type_which_could_be_long> (args) >>> >>> rather than >>> >>> std::unique_ptr<name_of_type_which_could_be_long> (new >>> name_of_type_which_could_be_long (args)); >>> >>>> >>>> >>>> >>>>> Is there: >>>>> (a) an easy way to implement a std::make_unique replacement >>>>> (e.g. in system.h? what to call it?), or >>>> >>>> If you don't care about using it to create unique_ptr<T[]> >>>> arrays, >>>> it's trivial: >>>> >>>> template<typename T, typename... Args> >>>> inline typename std::enable_if<!std::is_array<T>::value, >>>> std::unique_ptr<T>>::type >>>> make_unique(Args&&... args) >>>> { return std::unique_ptr<T>(new >>>> T(std::forward<Args>(args)...)); >>>> } >>>> >>>> To add the overload that works for arrays is a little trickier. >>> >>> Thanks! >>> >>> I tried adding it to gcc/system.h, but anything that uses it needs >>> to >>> have std::unique_ptr declared, which meant forcibly including >>> <memory> >>> from gcc/system.h >>> >>> So instead, here's a patch that adds a new gcc/make-unique.h >>> header, >>> containing just the template decl above (in the root namespace, >>> rather >>> than std::, which saves a bit more typing). >>> >> >> Adding things to std isn't allowed anyway, so that's correct. >> >> >>> I've successfully bootstrapped®ression-tested a version of my >>> earlier >>> analyzer patch that uses this patch (see patch 2 of the kit, which >>> has >>> lots of usage examples). >>> >>> OK for trunk? >>> >>> Dave > > [...snip...] > >>> +#ifndef INCLUDE_MEMORY >>> +# error "You must define INCLUDE_MEMORY before including system.h >>> to use >>> make-unique.h" >>> +#endif >>> >> >> You also need <type_traits> for the enable_if and is_array traits. >> With >> libstdc++ that gets included by <memory> but that's guaranteed for >> other >> library implementations. >> >> I don't know if that had the same kind of issues as other system >> headers or >> if it can just be included here. > > I've added an include of <type_traits> in this version of the patch. > >> >> >> + >>> +/* Minimal implementation of make_unique for C++11 compatibility >>> + (std::make_unique is C++14). */ >>> + >>> +template<typename T, typename... Args> >>> +inline typename std::enable_if<!std::is_array<T>::value, >>> std::unique_ptr<T>>::type >>> +make_unique(Args&&... args) >>> +{ >>> + return std::unique_ptr<T> (new T (std::forward<Args> >>> (args)...)); >>> +} >>> + >>> +#endif /* ! GCC_MAKE_UNIQUE */ >>> -- >>> 2.26.3 >>> >>> > > This patch adds gcc/make-unique.h, containing a minimal C++11 > implementation of make_unique (std::make_unique is C++14). > > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu > in conjunction with a followup series of patches which use this > in dozens of places in the analyzer. > > OK for trunk? OK. > gcc/ChangeLog: > * make-unique.h: New file. > --- > gcc/make-unique.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 44 insertions(+) > create mode 100644 gcc/make-unique.h > > diff --git a/gcc/make-unique.h b/gcc/make-unique.h > new file mode 100644 > index 00000000000..c9a7d6ef6ce > --- /dev/null > +++ b/gcc/make-unique.h > @@ -0,0 +1,44 @@ > +/* Minimal implementation of make_unique for C++11 compatibility. > + Copyright (C) 2022 Free Software Foundation, Inc. > + > +This file is part of GCC. > + > +GCC is free software; you can redistribute it and/or modify it under > +the terms of the GNU General Public License as published by the Free > +Software Foundation; either version 3, or (at your option) any later > +version. > + > +GCC is distributed in the hope that it will be useful, but WITHOUT ANY > +WARRANTY; without even the implied warranty of MERCHANTABILITY or > +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License > +for more details. > + > +You should have received a copy of the GNU General Public License > +along with GCC; see the file COPYING3. If not see > +<http://www.gnu.org/licenses/>. */ > + > +#ifndef GCC_MAKE_UNIQUE > +#define GCC_MAKE_UNIQUE > + > +/* This header uses std::unique_ptr, but <memory> can't be directly > + included due to issues with macros. Hence <memory> must be included > + from system.h by defining INCLUDE_MEMORY in any source file using > + make-unique.h. */ > + > +#ifndef INCLUDE_MEMORY > +# error "You must define INCLUDE_MEMORY before including system.h to use make-unique.h" > +#endif > + > +#include <type_traits> > + > +/* Minimal implementation of make_unique for C++11 compatibility > + (std::make_unique is C++14). */ > + > +template<typename T, typename... Args> > +inline typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type > +make_unique(Args&&... args) > +{ > + return std::unique_ptr<T> (new T (std::forward<Args> (args)...)); > +} > + > +#endif /* ! GCC_MAKE_UNIQUE */
diff --git a/gcc/make-unique.h b/gcc/make-unique.h new file mode 100644 index 00000000000..c9a7d6ef6ce --- /dev/null +++ b/gcc/make-unique.h @@ -0,0 +1,44 @@ +/* Minimal implementation of make_unique for C++11 compatibility. + Copyright (C) 2022 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 3, or (at your option) any later +version. + +GCC is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +<http://www.gnu.org/licenses/>. */ + +#ifndef GCC_MAKE_UNIQUE +#define GCC_MAKE_UNIQUE + +/* This header uses std::unique_ptr, but <memory> can't be directly + included due to issues with macros. Hence <memory> must be included + from system.h by defining INCLUDE_MEMORY in any source file using + make-unique.h. */ + +#ifndef INCLUDE_MEMORY +# error "You must define INCLUDE_MEMORY before including system.h to use make-unique.h" +#endif + +#include <type_traits> + +/* Minimal implementation of make_unique for C++11 compatibility + (std::make_unique is C++14). */ + +template<typename T, typename... Args> +inline typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type +make_unique(Args&&... args) +{ + return std::unique_ptr<T> (new T (std::forward<Args> (args)...)); +} + +#endif /* ! GCC_MAKE_UNIQUE */