C语言 为什么当前节点的int字段与链表中下一个节点的string字段相同?

Question

我正在编写一个使用链表保存信息的程序，这是头文件中结构体的定义。

structures.h:

typedef struct node* symbolPtr;
/* this will represent a member in the symbol table */
typedef struct node {
char name[32];
int address;

symbolPtr next;
} Symbol;

我注意到'address'字段的地址与下一个节点的'name'字段的地址相同，我不明白为什么。

这是主文件assembler.c:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "structures.h"

int firstRound(FILE*, symbolPtr, int*, int*);
int main() {
FILE *file;
int i;
int *IC, *DC;
symbolPtr smblTable;

IC = malloc(sizeof(int));
DC = malloc(sizeof(int));

smblTable = malloc(sizeof(Symbol));

smblTable->name[0] = '';
smblTable->next = NULL;


file = fopen("a.as", "r");


firstRound(file, smblTable, IC, DC);

free(IC);
free(DC);
free(smblTable);
return 0;
}

这就是问题所在的文件firstMove.c:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "structures.h"
static int addToSmblTable(char*, symbolPtr, int);
static void printAd(symbolPtr smblTable);
int firstRound(FILE *file, symbolPtr smblTable, int *IC, int *DC) {
char checker[32];

*IC = 100, *DC = 0;
/* this will go until we reach the end of the file */
for (; !feof(file);) {
fscanf(file, "%s", checker);

addToSmblTable(checker, smblTable, *DC);//this saves the value of *DC in the node
(*DC)++;
}

printAd(smblTable);// prints all the values of the linked list at the end

return 0;
}
static void printAd(symbolPtr smblTable) {
symbolPtr node;

for (node = smblTable; node->next; node = node->next) {
printf("n%s:   %p  %p  %dn", node->name, node->next->name, &(node->address), node->address);
//prints the string, the address of the next string and the address of the current 'address' field.
}
}

static symbolPtr getLastNode(char *, symbolPtr);

static int addToSmblTable(char *symbol, symbolPtr table, int address) {
symbolPtr node;



node = getLastNode(symbol, table);//the last node

if (node->name[0] != '') {
node->next = malloc(sizeof(symbol));
node = node->next;
}

/* saving the symbol */

strcpy(node->name, symbol);//here the address of the last node is being changed
node->address = address;



node->next = NULL;


return 0;
}

static symbolPtr getLastNode(char *symbol, symbolPtr table) {
symbolPtr node;

/* going over the symbol table and checking for the symbol */
node = table; 
while (node->next) {
node = node->next;
}

return node;
}

这是makefile:

test: assembler.o firstMove.o syntax.h structures.h
gcc -g -ansi -Wall -pedantic assembler.o firstMove.o -o test
assembler.o: assembler.c structures.h
gcc -c -g -ansi -Wall -pedantic assembler.c -o assembler.o
firstMove.o: firstMove.c structures.h
gcc -c -g -ansi -Wall -pedantic firstMove.c -o firstMove.o

假设这是a.as:

;file
;sample
.entry
.extern 
STR:
MAIN:
LOOP:
la
jmp
Next:
LIST:
bgt
la
sw
bne
call
jmp
la
.extern
.dh
K:
END:
.entry

那么输出如下:

In file a.as:
;file:  0x5566c6197920  0x5566c6196300  0
;sample:    0x5566c6197940  0x5566c6197940  1953391918
.entry: 0x5566c6197960  0x5566c6197960  1954047278
.extern:    0x5566c6197980  0x5566c6197980  978474067
STR::   0x5566c61979a0  0x5566c61979a0  1313423693
MAIN::  0x5566c61979c0  0x5566c61979c0  1347374924
LOOP::  0x5566c61979e0  0x5566c61979e0  24940
la: 0x5566c6197a00  0x5566c6197a00  7368042
jmp:    0x5566c6197a20  0x5566c6197a20  1954047310
Next::  0x5566c6197a40  0x5566c6197a40  1414744396
LIST::  0x5566c6197a60  0x5566c6197a60  7628642
bgt:    0x5566c6197a80  0x5566c6197a80  24940
la: 0x5566c6197aa0  0x5566c6197aa0  30579
sw: 0x5566c6197ac0  0x5566c6197ac0  6647394
bne:    0x5566c6197ae0  0x5566c6197ae0  1819042147
call:   0x5566c6197b00  0x5566c6197b00  7368042
jmp:    0x5566c6197b20  0x5566c6197b20  24940
la: 0x5566c6197b40  0x5566c6197b40  1954047278
.extern:    0x5566c6197b60  0x5566c6197b60  6841390
.dh:    0x5566c6197b80  0x5566c6197b80  14923
K:: 0x5566c6197ba0  0x5566c6197ba0  977555013
END::   0x5566c6197bc0  0x5566c6197bc0  1953391918
.entry: 0x5566c6197be0  0x5566c6197be0  1953391918

您可以看到，每个"address"字段的地址与下一个节点中"name"字段的地址相同。

为什么?我没有正确分配结构内存吗?

Answer 1

考虑一下这是在做什么

node->next = malloc(sizeof(symbol));

这里分配了多少字节?symbol是什么?

好了:

static int addToSmblTable(char *symbol, symbolPtr table, int address) {
symbolPtr node;

node = getLastNode(symbol, table);//the last node

if (node->name[0] != '') {
node->next = malloc(sizeof(symbol));

所以symbol是一个char*。您确定要为char指针分配内存吗?

这可能是一个简单的打字错误吗?symbol→Symbol

更好的方法是:

node->next = malloc(sizeof *(node->next));