c++pmr2.cpp - Simple C++17 PMR allocate/deallocate from multiple allocators demo
Posted by Anonymous on Tue 19th Nov 2024 10:00
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/*
 * c++pmr2.cpp - Simple C++17 PMR allocate/deallocate from multiple allocators demo
 *
 * Compile and run with
 * ---- snip ----
 * rm -f a.exe* ; clang++ -target x86_64-w64-mingw32 -std=c++17 -Bstatic c++pmr2.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++pmr2.cpp
 * ---- snip ----
 *
 * Output:
 * ---- snip ----
 * $ PATH+=':/usr/x86_64-w64-mingw32/sys-root/mingw/bin/' ./a.exe
 * # Cycle: 0: str='12'
 * # Cycle: 1: str='1212'
 * # Cycle: 2: str='12121212'
 * >> ALLOC(name='smirre',size=31), p=0xa00026e70
 * >> ALLOC(name='akka von kebnekaise',size=31), p=0xa000004f0
 * # Cycle: 3: str='1212121212121212'
 * >> ALLOC(name='smirre',size=31), p=0xa00026ef0
 * >> ALLOC(name='akka von kebnekaise',size=31), p=0xa00026f20
 * >> ALLOC(name='smirre',size=61), p=0xa00026f80
 * <<  FREE(name='smirre',p=0xa00026e70)
 * >> ALLOC(name='akka von kebnekaise',size=61), p=0xa00026fd0
 * <<  FREE(name='akka von kebnekaise',p=0xa000004f0)
 * # Cycle: 4: str='12121212121212121212121212121212'
 * >> ALLOC(name='smirre',size=61), p=0xa00027020
 * <<  FREE(name='smirre',p=0xa00026ef0)
 * >> ALLOC(name='akka von kebnekaise',size=61), p=0xa00027070
 * <<  FREE(name='akka von kebnekaise',p=0xa00026f20)
 * >> ALLOC(name='smirre',size=121), p=0xa000270c0
 * <<  FREE(name='smirre',p=0xa00026f80)
 * >> ALLOC(name='akka von kebnekaise',size=121), p=0xa00026ef0
 * <<  FREE(name='akka von kebnekaise',p=0xa00026fd0)
 * # Cycle: 5: str='1212121212121212121212121212121212121212121212121212121212121212'
 * >> ALLOC(name='smirre',size=121), p=0xa00026f80
 * <<  FREE(name='smirre',p=0xa00027020)
 * >> ALLOC(name='akka von kebnekaise',size=121), p=0xa00027150
 * <<  FREE(name='akka von kebnekaise',p=0xa00027070)
 * >> ALLOC(name='smirre',size=241), p=0xa000271e0
 * <<  FREE(name='smirre',p=0xa000270c0)
 * >> ALLOC(name='akka von kebnekaise',size=241), p=0xa00027020
 * <<  FREE(name='akka von kebnekaise',p=0xa00026ef0)
 * # Cycle: 6: str='12121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212'
 * >> ALLOC(name='smirre',size=241), p=0xa000272e0
 * <<  FREE(name='smirre',p=0xa00026f80)
 * >> ALLOC(name='akka von kebnekaise',size=241), p=0xa00026ef0
 * <<  FREE(name='akka von kebnekaise',p=0xa00027150)
 * >> ALLOC(name='smirre',size=481), p=0xa000274f0
 * <<  FREE(name='smirre',p=0xa000271e0)
 * >> ALLOC(name='akka von kebnekaise',size=481), p=0xa000276e0
 * <<  FREE(name='akka von kebnekaise',p=0xa00027020)
 * # Cycle: 7: str='1212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212'
 * >> ALLOC(name='smirre',size=481), p=0xa00026ff0
 * <<  FREE(name='smirre',p=0xa000272e0)
 * >> ALLOC(name='akka von kebnekaise',size=481), p=0xa000271e0
 * <<  FREE(name='akka von kebnekaise',p=0xa00026ef0)
 * >> ALLOC(name='smirre',size=961), p=0xa00027ae0
 * <<  FREE(name='smirre',p=0xa000274f0)
 * >> ALLOC(name='akka von kebnekaise',size=961), p=0xa00027eb0
 * <<  FREE(name='akka von kebnekaise',p=0xa000276e0)
 * 12121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212
 * <<  FREE(name='smirre',p=0xa00027ae0)
 * <<  FREE(name='akka von kebnekaise',p=0xa000271e0)
 * <<  FREE(name='smirre',p=0xa00026ff0)
 * <<  FREE(name='akka von kebnekaise',p=0xa00027eb0)
 * ---- snip ----
 *
 * Written by Roland Mainz <roland.mainz@nrubsig.org>
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <array>
#include <cstddef>
#include <iostream>
#include <memory_resource>

#define ARG_NOT_USED(a) ((void)(a))

#if 1
#define D(x) x
#else
#define D(x)
#endif

/*
 * C++ allocator implementation - do NOT use C++ functions here
 * for logging etc.
 */
class here_be_monsters : public std::pmr::synchronized_pool_resource {
        const char *name;
public:
        here_be_monsters(const char *name) {
                this->name = name;
        }
protected:
        void* do_allocate( std::size_t bytes, std::size_t alignment ) {
                void *p;
                ARG_NOT_USED(alignment);
                p = malloc(bytes);
                D((void)fprintf(stderr, ">> ALLOC(name='%s',size=%ld), p=%p\n", name, (long)bytes, p));
                D((void)fflush(stderr));
                return p;
        }

        void do_deallocate( void* p, std::size_t bytes, std::size_t alignment ) {
                ARG_NOT_USED(alignment);
                ARG_NOT_USED(bytes);
                D((void)fprintf(stderr, "<<  FREE(name='%s',p=%p)\n", name, p));
                D((void)fflush(stderr));
                free(p);
        }
};

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

        here_be_monsters pool1("akka von kebnekaise");
        here_be_monsters pool2("smirre");

        std::pmr::polymorphic_allocator<char> pa1{&pool1};
        std::pmr::polymorphic_allocator<char> pa2{&pool2};
        std::pmr::string s{"12", pa1};
        std::pmr::string s2{pa2};
        std::pmr::string s3{pa1};
        std::pmr::string s4{pa2};

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

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

        return EXIT_SUCCESS;
}