[devel] re APT patch with impossible error on "Can't allocate an item of size zero"
Aleksey Novodvorsky
aen на basealt.ru
Пн Фев 17 19:20:22 MSK 2020
пн, 17 февр. 2020 г., 17:06 Andrey Savchenko <bircoph на altlinux.org>:
> On Mon, 17 Feb 2020 11:41:36 +0300 (MSK) Ivan Zakharyaschev wrote:
> > Появилась идея, что есть способ здесь не просто ответственность
> возложить
> > на программиста на словах (вызывать Allocate() с ненулевым аргументом),
> но
> > и формально предложить такой способ программирования, где не будет
> > возможности делать не так, как задумано.
> >
> > Да и попроще вызовы получаются.
> >
> > Ветка alloc-templates в
> > http://git.altlinux.org/people/imz/packages/apt.git
> >
> > (Развивая это, можно RawAllocate() превратить в какой-нибудь
> > template<typename T> RawAllocateArray<T>(unsigned long ItemCount),
> > там, правда, Pools нетривиально надо будет переделать.
> >
> > Пришлось, правда, перенести определение из .cc в .h и патчи дальнейшие
> > неудобно прикладывать; но можно их ifdef-ами обложить в .cc и
> заинклудить
> > в .h.)
> >
> > From 89499e5810575336e6a3b02d71d6c323321a0eca Mon Sep 17 00:00:00 2001
> > From: Ivan Zakharyaschev <imz на altlinux.org>
> > Date: Fri, 14 Feb 2020 04:04:42 +0300
> > Subject: [PATCH] don't pass compile-time constants as an argument to
> > DynamicMMap::Allocate()
> >
> > The argument was used for the size of the item we want to allocate.
> >
> > Instead of an argument, use a parameter for the template
> DynamicMMap::Allocate()
> > which denotes the type of the item.
> >
> > Now, the truth of our assertion that the size is not zero is evident
> > (and checked by the compiler).
> >
> > Note that this change may also potentially lead to more optimized code
> > due to compile-time specialization for each particular size.
> > ---
> > apt/apt-pkg/contrib/mmap.h | 12 ++++++------
> > apt/apt-pkg/pkgcachegen.cc | 19 ++++++++++---------
> > apt/apt-pkg/pkgcachegen.h | 3 ++-
> > 3 files changed, 18 insertions(+), 16 deletions(-)
> >
> > diff --git a/apt/apt-pkg/contrib/mmap.h b/apt/apt-pkg/contrib/mmap.h
> > index 5b14ac9d9..7ec0fb8b1 100644
> > --- a/apt/apt-pkg/contrib/mmap.h
> > +++ b/apt/apt-pkg/contrib/mmap.h
> > @@ -94,7 +94,8 @@ class DynamicMMap : public MMap
> >
> > // Allocation
> > std::experimental::optional<unsigned long> RawAllocate(unsigned long
> Size,unsigned long Aln = 0);
> > - std::experimental::optional<unsigned long> Allocate(unsigned long
> ItemSize);
> > + template<typename T>
> > + std::experimental::optional<unsigned long> Allocate();
> > std::experimental::optional<unsigned long> WriteString(const char
> *String,unsigned long Len = std::numeric_limits<unsigned long>::max());
> > inline std::experimental::optional<unsigned long> WriteString(const
> string &S) {return WriteString(S.c_str(),S.length());};
> > void UsePools(Pool &P,unsigned int Count) {Pools = &P; PoolCount =
> Count;};
> > @@ -107,17 +108,16 @@ class DynamicMMap : public MMap
> > /* Templates */
> >
> > #include <apt-pkg/error.h>
> > -#include <cassert>
> >
> > // DynamicMMap::Allocate - Pooled aligned allocation
> /*{{{*/
> > // ---------------------------------------------------------------------
> > /* This allocates an Item of size ItemSize so that it is aligned to its
> > size in the file. */
> > -std::experimental::optional<unsigned long>
> DynamicMMap::Allocate(unsigned long ItemSize)
> > +template<typename T>
> > +std::experimental::optional<unsigned long> DynamicMMap::Allocate()
> > {
> > - assert(ItemSize != 0); /* Actually, we are always called with
> sizeof(...)
> > - compile-time non-zero constant as the
> argument.
> > - */
> > + constexpr unsigned long ItemSize = sizeof(T);
> > + static_assert(ItemSize != 0);
>
> Давайте не закладываться на C++17:
> https://en.cppreference.com/w/cpp/language/static_assert
+1.
Чтобы не было проблем с бекпортированием. В том числе на e2k.
Rgrds, Алексей
>
>
> static_assert ( bool_constexpr , message ) (since C++11)
> static_assert ( bool_constexpr ) (since C++17)
>
> Так что прошу использовать первую форму (C++11 с сообщением)
> и убедится, что явно задан как минимум -std=c++11/gnu++11.
>
> >
> > // Look for a matching pool entry
> > Pool *I;
> > diff --git a/apt/apt-pkg/pkgcachegen.cc b/apt/apt-pkg/pkgcachegen.cc
> > index 4bbab07bf..2a75f31e6 100644
> > --- a/apt/apt-pkg/pkgcachegen.cc
> > +++ b/apt/apt-pkg/pkgcachegen.cc
> > @@ -112,8 +112,9 @@ std::experimental::optional<unsigned long>
> pkgCacheGenerator::WriteStringInMap(c
> > return Map.WriteString(String);
> > }
> >
> /*}}}*/
> > -std::experimental::optional<unsigned long>
> pkgCacheGenerator::AllocateInMap(unsigned long size) {/*{{{*/
> > - return Map.Allocate(size);
> > +template<typename T>
> > +std::experimental::optional<unsigned long>
> pkgCacheGenerator::AllocateInMap() {/*{{{*/
> > + return Map.Allocate<T>();
> > }
> >
> /*}}}*/
> > // CacheGenerator::MergeList - Merge the package list
> /*{{{*/
> > @@ -376,7 +377,7 @@ bool
> pkgCacheGenerator::NewPackage(pkgCache::PkgIterator &Pkg, const string &Nam
> > #endif
> >
> > // Get a structure
> > - const auto Package = AllocateInMap(sizeof(pkgCache::Package));
> > + const auto Package = AllocateInMap<pkgCache::Package>();
> > const auto idxName = WriteStringInMap(Name);
> > if ((!Package) || (!idxName))
> > return false;
> > @@ -429,7 +430,7 @@ bool
> pkgCacheGenerator::NewFileVer(pkgCache::VerIterator &Ver,
> > return true;
> >
> > // Get a structure
> > - const auto VerFile = AllocateInMap(sizeof(pkgCache::VerFile));
> > + const auto VerFile = AllocateInMap<pkgCache::VerFile>();
> > if (!VerFile)
> > return false;
> >
> > @@ -460,7 +461,7 @@ std::experimental::optional<unsigned long>
> pkgCacheGenerator::NewVersion(pkgCach
> > unsigned long Next)
> > {
> > // Get a structure
> > - const auto Version = AllocateInMap(sizeof(pkgCache::Version));
> > + const auto Version = AllocateInMap<pkgCache::Version>();
> > const auto idxVerStr = WriteStringInMap(VerStr);
> > if ((!Version) || (!idxVerStr))
> > return std::experimental::nullopt;
> > @@ -487,7 +488,7 @@ bool
> pkgCacheGenerator::ListParser::NewDepends(pkgCache::VerIterator &Ver,
> > pkgCache &Cache = Owner->Cache;
> >
> > // Get a structure
> > - const auto Dependency =
> Owner->AllocateInMap(sizeof(pkgCache::Dependency));
> > + const auto Dependency = Owner->AllocateInMap<pkgCache::Dependency>();
> > if (!Dependency)
> > return false;
> >
> > @@ -574,7 +575,7 @@ bool
> pkgCacheGenerator::ListParser::NewProvides(pkgCache::VerIterator &Ver,
> > }
> > }
> > // Get a structure
> > - const auto Provides =
> Owner->AllocateInMap(sizeof(pkgCache::Provides));
> > + const auto Provides = Owner->AllocateInMap<pkgCache::Provides>();
> > if (!Provides)
> > return false;
> > /* Note:
> > @@ -618,7 +619,7 @@ bool pkgCacheGenerator::SelectFile(const string
> &File, const string &Site,
> > unsigned long Flags)
> > {
> > // Get some space for the structure
> > - const auto idxFile = AllocateInMap(sizeof(*CurrentFile));
> > + const auto idxFile = AllocateInMap<decltype(*CurrentFile)>();
> > const auto idxFileName = WriteStringInMap(File);
> > const auto idxSite = WriteUniqString(Site);
> > const auto idxIndexType = WriteUniqString(Index.GetType()->Label);
> > @@ -676,7 +677,7 @@ std::experimental::optional<unsigned long>
> pkgCacheGenerator::WriteUniqString(co
> > }
> >
> > // Get a structure
> > - const auto Item = AllocateInMap(sizeof(pkgCache::StringItem));
> > + const auto Item = AllocateInMap<pkgCache::StringItem>();
> > const auto idxString = WriteStringInMap(S, Size);
> > if ((!Item) || (!idxString))
> > return std::experimental::nullopt;
> > diff --git a/apt/apt-pkg/pkgcachegen.h b/apt/apt-pkg/pkgcachegen.h
> > index b789177ef..73252802b 100644
> > --- a/apt/apt-pkg/pkgcachegen.h
> > +++ b/apt/apt-pkg/pkgcachegen.h
> > @@ -39,7 +39,8 @@ class pkgCacheGenerator
> > std::experimental::optional<unsigned long> WriteStringInMap(const
> std::string &String) { return WriteStringInMap(String.c_str(),
> String.length()); };
> > std::experimental::optional<unsigned long> WriteStringInMap(const
> char *String);
> > std::experimental::optional<unsigned long> WriteStringInMap(const
> char *String, unsigned long Len);
> > - std::experimental::optional<unsigned long> AllocateInMap(unsigned
> long size);
> > + template<typename T>
> > + std::experimental::optional<unsigned long> AllocateInMap();
> >
> > public:
> >
>
>
> Best regards,
> Andrew Savchenko
> _______________________________________________
> Devel mailing list
> Devel на lists.altlinux.org
> https://lists.altlinux.org/mailman/listinfo/devel
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