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C数据类型与内存大小深度解析

1. 内存大小与类型的关系

#include<stdio.h>#include<stdint.h>#include<stddef.h>intmain(){// 1. 基本类型的大小（单位：字节）printf("=== 基本数据类型大小 ===\n");printf("char: %2zu 字节\n",sizeof(char));printf("short: %2zu 字节\n",sizeof(short));printf("int: %2zu 字节\n",sizeof(int));printf("long: %2zu 字节\n",sizeof(long));printf("long long: %2zu 字节\n",sizeof(longlong));printf("float: %2zu 字节\n",sizeof(float));printf("double: %2zu 字节\n",sizeof(double));printf("long double: %2zu 字节\n",sizeof(longdouble));printf("void*: %2zu 字节（指针大小）\n",sizeof(void*));// 2. 固定宽度整数类型（C99标准）printf("\n=== 固定宽度整数类型 ===\n");printf("int8_t: %2zu 字节，范围: %d 到 %d\n",sizeof(int8_t),INT8_MIN,INT8_MAX);printf("uint8_t: %2zu 字节，范围: 0 到 %u\n",sizeof(uint8_t),UINT8_MAX);printf("int16_t: %2zu 字节，范围: %d 到 %d\n",sizeof(int16_t),INT16_MIN,INT16_MAX);printf("uint16_t: %2zu 字节，范围: 0 到 %u\n",sizeof(uint16_t),UINT16_MAX);printf("int32_t: %2zu 字节，范围: %d 到 %d\n",sizeof(int32_t),INT32_MIN,INT32_MAX);printf("uint32_t: %2zu 字节，范围: 0 到 %u\n",sizeof(uint32_t),UINT32_MAX);printf("int64_t: %2zu 字节，范围: %lld 到 %lld\n",sizeof(int64_t),INT64_MIN,INT64_MAX);printf("uint64_t: %2zu 字节，范围: 0 到 %llu\n",sizeof(uint64_t),UINT64_MAX);// 3. 内存对齐的重要性printf("\n=== 结构体内存对齐 ===\n");structUnaligned{chara;// 1字节intb;// 4字节charc;// 1字节}unaligned;structAligned{intb;// 4字节chara;// 1字节charc;// 1字节}aligned;printf("非对齐结构体大小: %zu 字节\n",sizeof(unaligned));printf("优化对齐结构体大小: %zu 字节\n",sizeof(aligned)