一段源码， Visual Studio 2019 上编译不成功， Linux 上可以

把指针变量 str 稍微修改了一下，现在 VS2019 编译不会出错了，但是 Windows 平台和 Linux 平台的结果为什么会不一样

结果

# Linux下 value is 757731736816714497 Received 'A84010000000301' # Windows下 value is 4294967295 Received 'FFFFFFFF' 

源码

#include <stdio.h> #include <stdlib.h> #include <string.h> /* unsigned long to string */ char * ultostr(unsigned long value, char * ptr, int base); int main(void) { char var[] = "0A84010000000301"; unsigned long value = strtoul(var, NULL, 16); printf("value is %lu\n\n", value); int size = sizeof(var); char * str = malloc(size + 1); ultostr(value, str, 16); printf("Received '%s'\n\n",str); return 0; } /* unsigned long to string */ char* ultostr(unsigned long value, char* ptr, int base) { unsigned long t = 0, res = 0; unsigned long tmp = value; int count = 0; if (NULL == ptr) { return NULL; } if (tmp == 0) { count++; } while (tmp > 0) { tmp = tmp / base; count++; } ptr += count; *ptr = '\0'; do { res = value - base * (t = value / base); if (res < 10) { *--ptr = '0' + res; } else if ((res >= 10) && (res < 16)) { *--ptr = 'A' - 10 + res; } } while ((value = t) != 0); return(ptr); } 

经 @ysc3839 指点，使用 unsigned long long 数据类型就可以使 Windows上与Linux上结果一致了。

感谢各位的帮助！

更正后

#include <stdio.h> #include <stdlib.h> #include <string.h> /* unsigned long long to string */ char * ultostr(unsigned long long value, char * ptr, int base); int main(void) { char var[] = "0A84010000000301"; unsigned long long value = strtoull(var, NULL, 16); printf("value is %llu\n", value); int size = sizeof(var); char * str = malloc(size); ultostr(value, str, 16); printf("Received '%s'\n",str); free(str); return 0; } /* unsigned long long to string */ char* ultostr(unsigned long long value, char * ptr, int base) { unsigned long long t = 0, res = 0; unsigned long long tmp = value; int count = 0; if (NULL == ptr) { return NULL; } if (tmp == 0) { count++; } while (tmp > 0) { tmp = tmp / base; count++; } ptr += count; *ptr = '\0'; do { res = value - base * (t = value / base); if (res < 10) { *--ptr = '0' + re; } else if ((res >= 10) && (res < 16)) { *--ptr = 'A' - 10 + res; } } while ((value = t) != 0); return(ptr); }