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10votes
2answers
584views
How can I iterate a flat_map in a range-based 'for' loop, updating values?
It is easy to iterate std::map and update values:#include <iostream>#include <map>int main() { std::map<int, int> m; m[1] = 2; m[2] = 4; for (auto &[k, v] : m)...
Best practices
0votes
11replies
223views
c++ abstract class : pure virtual covariant return
first I must says that I hate templates.... it makes unreadable complex code.... not speaking about 5000000 lines long error messages, with 10000 possibilities and that takes ages to understand for ...
5votes
1answer
131views
Can you observe whether _Atomic expands to an alias template or class template?
[stdatomics.h.syn] specifies the following:template<class T> using std-atomic = std::atomic<T>; // exposition only#define _Atomic(T) std-atomic<T>libc++ and libstdc++ ...
- 44.3k
Advice
0votes
5replies
98views
Can overusing the [[assume]] attribute cause problems?
I wonder if using the [[assume]] attribute can have negative effects on my code, even if the expressions inside are always true.In my code, I defined the following macro:#ifdef DEBUG #include &...
- 337
2votes
0answers
54views
libstdc++.so links error when try to use pybind11/3.0.1 of conan-2 and cpp23 in wsl
In WSL (Ubuntu 24.04), when using Conan to create a package that links pybind11/3.0.1, the resulting executable in the test_package fails to run.Even if the executable doesn't directly call any ...
- 21
0votes
1answer
133views
Is it well-formed to track POD class layouts at compile time?
I'm trying to generate compile-time info about my POD types. Getting the offset of each member has been challenging due to limitations like no pointer conversions in constexpr, but I think I've found ...
11votes
1answer
316views
How can you prevent a destructor call from being reordered above an atomic write by the compiler?
Here is a possibly incorrect program for communicating between a function and a signal handler that might interrupt it. Assume that HandleSignal has been arranged to run as a signal handler. The ...
- 7,905
2votes
2answers
197views
How to return a list of selected elements of some underlying container in a typesafe manner?
Im wondering if there is a better, more typesafe, way to return "a selection" than I do at the moment.If we only ever have one selected element at a time, we can just return a reference, ...
- 11.5k
6votes
2answers
261views
Forwarding multiple sets of variadic arguments
I'm building a container which uses, as its internal representation, a couple of standard containers, each with a different type. I need to code my version of emplace(..) and here's where I got stuck....
- 1,088
2votes
0answers
166views
timespec, timespec_get not found in the std namespace and TIME_MONOTONIC not defined
I was trying to learn about how to use timespec_get in c++ (for fun)I tried to compile the following code using g++ 14.1.0//main.cpp#include <ctime>int main(){ std::timespec CurrentTime;...
- 711
1vote
0answers
84views
How to make IntelliSense work properly with MSVC standard library and clang-cl compiler?
I'm trying to get clang-cl (the compiler I installed via Visual Studio Installer), MSVC standard library and IntelliSense to work together.Simple 'Hello world' by C++23 std::println does build and ...
1vote
1answer
455views
Apple Clang 21 unable to compile with c++ 23 stacktrace header
I am trying to use the C++ 23 stacktrace header in my project but I can't get it to compile. I've reproduced this with a minimal case to demonstrate the error I am getting. Any input would be greatly ...
- 29
2votes
1answer
137views
C++ Template Function Ambiguity for Wrapper Type Specialization
I have a C++ function template:#include <string_view>template<typename T>T get_gadget(std::string_view str);I also added explicit specializations for some user-defined types, e.g., ...
- 393
6votes
1answer
245views
How do I create and use a stack-allocated struct ending with a C99 flexible array member in C++ without undefined behaviour?
I'm calling a 3rd-party C99 library from modern C++. The API contains a struct that ends with a flexible array member. To allocate the struct on the stack I think I need a byte buffer then cast it to ...
- 1,295
-1votes
1answer
203views
Typename packing is failed in C++
Here is code:aml::type_list<int,int,char,std::string> example;std::tuple_element_t<2,std::tuple<decltype(example)>> a = 'b';But when i try to run code it says, static assertion ...
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