c++pmr1.cpp PMR buffer too small test 1
Posted by Anonymous on Mon 18th Nov 2024 08:48
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modification of post by Anonymous (view diff)


/*
 * c++pmr1.cpp - Simple C++17 PMR example+out-of-memory condition
 *
 * Compile and run with
 * ---- snip ----
 * rm -f a.exe* ; clang++ -target x86_64-w64-mingw32 -std=c++17 -Bstatic c++pmr1.cpp
 * ---- snip ----
 * OR (Cygwin 3.6 with gcc 15.0):
 * ---- snip ----
 * rm -f a.exe* ; g++ -std=c++20 -Wall -Wextra -D_GLIBCXX_USE_CXX11_ABI c++pmr1.cpp
 * ---- snip ----
 *
 * Output:
 * ---- snip ----
 * $ PATH+=':/usr/x86_64-w64-mingw32/sys-root/mingw/bin/' ./a.exe
 * # Cycle: 0: str='x'
 * # Cycle: 1: str='xx'
 * # Cycle: 2: str='xxxx'
 * # Cycle: 3: str='xxxxxxxx'
 * # Cycle: 4: str='xxxxxxxxxxxxxxxx'
 * DIE!!std::bad_alloc
 * ---- snip ----
 *
 * Written by Roland Mainz <roland.mainz@nrubsig.org>
 */

#include <array>
#include <cstddef>
#include <iostream>
#include <memory_resource>


int main(int ac, char *av[])
{
        char buffer[4096];

        /*
         * Note that without |std::pmr::null_memory_resource()| |monotonic_buffer_resource()| will
         * use the default memory resource to obtain memory if it runs out of memory
         */
        std::pmr::monotonic_buffer_resource pool{buffer, sizeof(buffer), std::pmr::null_memory_resource() };
        std::pmr::polymorphic_allocator<char> pa{&pool};
        std::pmr::string s{"12", pa};
        std::pmr::string s2{pa};
        std::pmr::string s3{pa};
        std::pmr::string s4{pa};

        try {
                for (int i=0 ; i < 8 ; i++) {
                        std::cout << "# Cycle: " << i << ": str='" << s << "'" << std::endl;
                        s2 = s;
                        s3 = s;
                        s4 = s2 + s3;
                        s = s4;
                }

                std::cout << s << std::endl;
        } catch(const std::exception &e) {
                std::cerr << "DIE!!" << e.what() << std::endl;
        }

        return EXIT_SUCCESS;
}