Yes, ISO C++ allows (but doesn’t require) implementations to make this choice. But also note that ISO C++ allows a compiler to emit code that crashes on purpose (e.g. with an illegal instruction) if the program encounters UB, e.g. as a way to help you find errors. (Or because it’s a DeathStation 9000. Being strictly … Read more
#include <cstdio> #include <iostream> #include <memory> #include <stdexcept> #include <string> #include <array> std::string exec(const char* cmd) { std::array<char, 128> buffer; std::string result; std::unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd, “r”), pclose); if (!pipe) { throw std::runtime_error(“popen() failed!”); } while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr) { result += buffer.data(); } return result; } Pre-C++11 version: #include <iostream> #include <stdexcept> #include … Read more
Depends on what you want to do: to read the value as an ascii code, you can write char a=”a”; int ia = (int)a; /* note that the int cast is not necessary — int ia = a would suffice */ to convert the character ‘0’ -> 0, ‘1’ -> 1, etc, you can write … Read more
For all the standard library types the member function empty() is a query, not a command, i.e. it means “are you empty?” not “please throw away your contents”. The clear() member function is inherited from ios and is used to clear the error state of the stream, e.g. if a file stream has the error … Read more
C++11 update to a very old question: Print variable type in C++. The accepted (and good) answer is to use typeid(a).name(), where a is a variable name. Now in C++11 we have decltype(x), which can turn an expression into a type. And decltype() comes with its own set of very interesting rules. For example decltype(a) … Read more
Unless you are forced to use C, you should never use malloc. Always use new. If you need a big chunk of data just do something like: char *pBuffer = new char[1024]; Be careful though this is not correct: //This is incorrect – may delete only one element, may corrupt the heap, or worse… delete … Read more
The standard tool for listing symbols is nm, you can use it simply like this: nm -gD yourLib.so If you want to see symbols of a C++ library, add the “-C” option which demangle the symbols (it’s far more readable demangled). nm -gDC yourLib.so If your .so file is in elf format, you have two … Read more
Modern C++ makes this super simple. C++20 C++20 introduces std::format, which allows you to do exactly that. It uses replacement fields similar to those in python: #include <iostream> #include <format> int main() { std::cout << std::format(“Hello {}!\n”, “world”); } Code from cppreference.com, CCÂ BY-SA and GFDL Check out the compiler support page to see if it’s … Read more
The C++ standard guarantees the following: static_casting a pointer to and from void* preserves the address. That is, in the following, a, b and c all point to the same address: int* a = new int(); void* b = static_cast<void*>(a); int* c = static_cast<int*>(b); reinterpret_cast only guarantees that if you cast a pointer to a … Read more
Use map::find and map::end: if (m.find(“f”) == m.end()) { // not found } else { // found }