#include struct Code1 : Xbyak::CodeGenerator { Code1() : Xbyak::CodeGenerator(4096, Xbyak::DontSetProtectRWE) { mov(eax, 123); ret(); } void update() { db(0); } }; void test1(bool updateCode) { Code1 c; c.setProtectModeRE(); if (updateCode) c.update(); // segmentation fault int (*f)() = c.getCode(); printf("f=%d\n", f()); c.setProtectModeRW(); c.update(); puts("ok"); } struct Code2 : Xbyak::CodeGenerator { Code2() : Xbyak::CodeGenerator(4096, Xbyak::AutoGrow) { mov(eax, 123); ret(); } void update() { db(0); } }; void test2(bool updateCode) { Code2 c; c.readyRE(); if (updateCode) c.update(); // segmentation fault int (*f)() = c.getCode(); printf("f=%d\n", f()); c.setProtectModeRW(); c.update(); puts("ok"); } int main(int argc, char *argv[]) { if (argc < 2) { fprintf(stderr, "%s [update]\n", argv[0]); return 0; } bool update = argc == 3; int n = atoi(argv[1]); printf("n=%d update=%d\n", n, update); switch (n) { case 1: test1(update); break; case 2: test2(update); break; default: fprintf(stderr, "no test %d\n", n); break; } }