Allocator | Ultra fast C++11 allocator for STL containers | 3D Printing library
kandi X-RAY | Allocator Summary
kandi X-RAY | Allocator Summary
Fast C++11 allocator for STL containers.
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Lines of Code : 3License : Non-SPDX (Apache License 2.0)
Copydef allocator(self):
"""Name of the allocator used to create this tensor (string)."""
return self._allocator Community Discussions
Trending Discussions on Allocator
QUESTION
I am trying to use a custom allocator, using the allocator API in Rust.
It seems Rust considers Vec and Vec as two distinct types.
ANSWER
Answered 2022-Mar-28 at 09:53Update:
Since GitHub pull request #93755 has been merged, comparison between Vecs with different allocators is now possible.
Original answer:
Vec uses the std::alloc::Global allocator by default, so Vec is in fact Vec. Since Vec and Vec are indeed distinct types, they cannot directly be compared because the PartialEq implementation is not generic for the allocator type. As @PitaJ commented, you can compare the slices instead using assert_eq!(&a[..], &b[..]) (which is also what the author of the allocator API recommends).
QUESTION
In my version of clang and libc++ (near HEAD), this static_assert passes:
ANSWER
Answered 2022-Mar-26 at 23:21std::vector and other containers (except std::array) are specified to have a copy constructor. This is not specified to be conditional on whether or not the element type is copyable. Only instantiation of the copy constructor's definition is forbidden if the element type is not copyable.
As a result std::is_copy_constructible_v on the container will always be true. There is no way to test whether an instantiation of a definition would be well-formed with a type trait.
It would be possible to specify that the copy constructor is not declared or excluded from overload resolution if the element type is not copyable. However, that would come with a trade-off which is explained in detail in this blog post: https://quuxplusone.github.io/blog/2020/02/05/vector-is-copyable-except-when-its-not/.
In short, if we want to be able to use the container with an incomplete type, e.g. recursively like
QUESTION
I'm experimenting with Hunspell and how to interact with it using Java Project Panama (Build 19-panama+1-13 (2022/1/18)). I was able to get some initial testing done, as in creating a handle to Hunspell and subsequently using that to perform a spell check. I'm now trying something more elaborate, letting Hunspell give me suggestions for a word not present in the dictionary. This is the code that I have for that now:
ANSWER
Answered 2022-Feb-24 at 21:41Looking at the header here: https://github.com/hunspell/hunspell/blob/master/src/hunspell/hunspell.h#L80
QUESTION
I had a problem with include order that I cannot explain. I will show you a minimal example with four files:
...ANSWER
Answered 2022-Feb-24 at 14:53I tested the same code in Visual Studio 2022 and got the same error. After my exploration, I found the problem.
Firstly, I copied the contents of A.h and B.h into main.cpp and removed the #include directive. After compiling, I still got the same error.
Then I tested and found that as soon as I moved namespace std {...} after the definition of class B, the error went away.
I read the assembly code generated by the compiler and found that the names generated for GetMap in main.cpp and b.cpp are different:
main.asm:
GetMap@B@@QEBAAEBV?$unordered_map@UA@@HV?$hash@UA@@@std@@U?$equal_to@UA@@@3@V?$allocator@U?$pair@$$CBUA@@H@std@@@3@@std@@XZ
b.asm:
GetMap@B@@QEBAAEBV?$unordered_map@UA@@HU?$hash@UA@@@std@@U?$equal_to@UA@@@3@V?$allocator@U?$pair@$$CBUA@@H@std@@@3@@std@@XZ
I looked up MSVC's name mangling rules and found U for struct and V for class. So I change the definition of template<> class hash to template<> struct hash. Then the error disappeared.
I think it's legal to use class keyword instead in the specialization, but I can't find a description of this in the standard.
However, I think the problem may not be that simple. A key issue here is that the specialization of std::hash in B.cpp appears after the definition of class B, while in main.cpp the order is completely reversed. I think this violates the ODR and should result in undefined behavior. This is also why the program is correct after swapping the order of the header files (making it consistent with the order in B.cpp).
I looked up some sources and couldn't find a standard description of the problem: In B.cpp, the declaration of GetMap does not cause unordered_map to be instantiated, but it is instantiated in the function definition. A specialization of std::hash was inserted in the middle of declaration and definition, which could cause unordered_map to see a different definition of std::hash. Can the compiler see this specialization? Should the compiler choose this specialization? If the compiler can see the specialization, why is the primary template used in the generated assembly code? (The compiler-generated name in B.cpp uses "U", which is for struct)
QUESTION
I'm working on an Advent of Code challenge (2021 day 18). Just as a test I tried compiling it on different compilers. While GCC (11.2) and MSVC (19.30) think it's fine, Clang (13.0.0) throws a list of errors. link to compiler explorer
...ANSWER
Answered 2022-Feb-05 at 10:17Your type is an aggregate
QUESTION
Discussion about this was started under this answer for quite simple question.
ProblemThis simple code has unexpected overload resolution of constructor for std::basic_string:
ANSWER
Answered 2022-Jan-05 at 12:05Maybe I'm wrong, but it seems that last part:
QUESTION
Recently, I became interested in tracking memory allocation and deallocation. When overloading the new and delete operators, I found that the C++ standard library sometimes calls the overloaded operators and sometimes allocates memory using other methods. (Probably std::allocator.) For instance, std::string seems not to use new. Although, std::vector seems to call new when push_back is called. This is surprising since I would think the standard library would have a uniform policy to manage memory allocation.
When does the standard library choose to new vs std::allocator? Why?
ANSWER
Answered 2022-Jan-12 at 10:28The standard containers will use the allocator provided to them to allocate dynamic memory. By default, that is std::allocator.
For most other dynamic memory uses in the standard library, the standard doesn't specify how the implementation should acquire memory, and the implementation has the freedom to do what they want.
As for tracking memory allocations, I recommend wrapping malloc.
QUESTION
The following code
...ANSWER
Answered 2022-Jan-11 at 09:42The bug has been fixed and the example now compiles.
QUESTION
I am trying to use the video_player, but I am getting the below error. I have also added an MRE (minimum reproducible example).
I have used an emulated Pixel 4, an emulated Pixel 4 XL, and an emulator Pixel 5 with the Android Studio Beta, but none of them worked.
The below error was when I was using a Pixel 4 XL, but the error was the same with all of them.
Error:
...ANSWER
Answered 2022-Jan-11 at 08:53It can be a bug of that Flutter package, indeed. Have you tried to create an issue in GitHub of that package?
Secondly, during my development, I see several times when emulators just fail and real devices always work. The solution I used is - simply to do not test them on simulators. Real users never use simulators, aren't they?
It can be a bug of the library when running on x86 arch (the arch simulators use). Then, nobody with a real device (arm arch) will ever see the bug.
Thirdly, what about trying to use "cloud real devices" to test whether they work on real Pixel devices that you are worried about. There are many platforms that host some real devices and you can connect to them via a webpage and test your app.
QUESTION
I try to run codes like
...ANSWER
Answered 2021-Dec-23 at 05:31Assuming you are using Microsoft's C/C++ extension, you must configure the extension to use C++ 20 standard for intellisense.
The easiest way to do this is to add the line "C_Cpp.default.cppStandard": "c++20" to your settings.json file. You can also find the setting in the GUI under the name "Cpp Standard". Selecting c++20 from its dropdown will achieve the same result.
Note that this setting is, by default, set as a global user defaults. You can configure it per-workspace by selecting the Workspace tab in the settings GUI and changing that Cpp Standard dropdown to c++20.
As for why adding the -std=c++20 flag didn't work: -std=c++20 just tells your compiler which standard to use to build your code. 'Intellisense' does not receive this flag because it is a separate tool from the compiler and is therefore not required to support all the standards the compiler supports. It may support less even, although Intellisense tools usually support as current a standard as possible. Therefore the language standard for Intellisense must be configured separately from the compiler (in this case).
Final Note: After changing the setting, try closing and re-opening VS Code. In my experience changing the language standard setting can cause some weirdness to happen. Closing and re-opening VS Code seems to ensure the setting changes take full effect.
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