我知道Segmentation Fault表示我试图访问不应该/尚未分配的内存，但在代码中找不到触发此错误的原因。其他答案指向使用Valgrind，但我的本地机器上没有编译器，也没有在学校服务器上安装它的管理权限。如有任何帮助指出错误发生的位置，我们将不胜感激。这是头文件
/*
* File: set.h
*
* Copyright: 2015, Darren C. Atkinson
*
* Description: This file contains the public function and type
* declarations for a set abstract data type for strings. A
* set is an unordered collection of distinct elements.
*
* Note that this file uses the bool type, but does not define
* it. You should include <stdbool.h> beforehand.
*/
# ifndef SET_H
# define SET_H
typedef struct set
{
char **elts; //char * array containing strings
int length; //total length of array
int size; //number of strings within array
}SET;
SET *createSet(int maxElts);
void destroySet(SET *sp);
int numElements(SET *sp);
bool hasElement(SET *sp, char *elt);
bool addElement(SET *sp, char *elt);
bool removeElement(SET *sp, char *elt);
# endif /* SET_H */
要用我的代码编译的给定测试文件。
/*
* File: unique.c
*
* Copyright: 2015, Darren C. Atkinson
*
* Description: This file contains the main function for testing a set
* abstract data type for strings.
*
* The program takes two files as command line arguments, the
* second of which is optional. All words in the first file
* are inserted into the set and the counts of total words and
* total words in the set are printed. If the second file is
* given then all words in the second file are deleted from
* the set and the count printed.
*/
# include <stdio.h>
# include <stdlib.h>
# include <string.h>
# include <stdbool.h>
# include "set.h"
/* This is sufficient for the test cases in /scratch/coen12. */
# define MAX_SIZE 18000
/*
* Function: main
*
* Description: Driver function for the test application.
*/
int main(int argc, char *argv[])
{
FILE *fp;
char buffer[BUFSIZ];
SET *unique;
int words;
/* Check usage and open the first file. */
if (argc == 1 || argc > 3) {
fprintf(stderr, "usage: %s file1 [file2]n", argv[0]);
exit(EXIT_FAILURE);
}
if ((fp = fopen(argv[1], "r")) == NULL) {
fprintf(stderr, "%s: cannot open %sn", argv[0], argv[1]);
exit(EXIT_FAILURE);
}
/* Insert all words into the set. */
words = 0;
unique = createSet(MAX_SIZE);
while (fscanf(fp, "%s", buffer) == 1) {
words ++;
addElement(unique, buffer);
}
printf("%d total wordsn", words);
printf("%d distinct wordsn", numElements(unique));
fclose(fp);
/* Try to open the second file. */
if (argc == 3) {
if ((fp = fopen(argv[2], "r")) == NULL) {
fprintf(stderr, "%s: cannot open %sn", argv[0], argv[2]);
exit(EXIT_FAILURE);
}
/* Delete all words in the second file. */
while (fscanf(fp, "%s", buffer) == 1)
removeElement(unique, buffer);
printf("%d remaining wordsn", numElements(unique));
}
destroySet(unique);
exit(EXIT_SUCCESS);
}
最后是我的代码，这是错误应该产生的地方。
/*
* File: unsorted.c
*
*
* Description: This file contains the definitions for a simple interface for a SET structure that contains a list of strings as well as the list size.
*/
#include <assert.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include "set.h"
int findElement(SET *sp,char *elt);
struct SET
{
char **elts; //char * array containing strings
int length; //total length of array
int size; //number of strings within array
};
//initializes SET
//O(1) efficiancy
SET *createSet(int maxElts)
{
SET *sp;
sp->elts = (char **) malloc(sizeof(char*)*maxElts);
assert(sp->elts!=NULL);
sp->size = 0;
sp->length = maxElts;
return sp;
}
//frees all strings from memory and then the containing array
//O(n) efficiancy n==sp->size
void destroySet(SET *sp)
{
while (sp->size > 0) free(sp->elts[--sp->size]);
free(sp->elts);
}
//return the number of strings within the array
//O(1) efficiency
int numElements(SET *sp)
{
return sp->size;
}
//Sequentially searches SET for elt and return the array location, if not found -1 is returned
//O(n) efficiency n=sp->size
int findElement(SET *sp,char *elt)
{
int i =0;
for (i; i < sp->size; i++)
{
if (strcmp(sp->elts[i],elt) == 0) return i;
}
return -1;
}
//appends elt on the end of the array within SET
//O(1) efficiency
bool addElement(SET *sp, char *elt)
{
if (findElement(sp, elt) != -1) return false;
if (sp->size == sp->length) return false;
sp->elts[sp->size] = (char*) malloc(sizeof(char)*(strlen(elt)+1));
assert(sp->elts[sp->size]!=NULL);
sp->size = sp->size +1;
return true;
}
//returns true if SET contains elt otherwise return false
//O(n) efficiency n=sp->size
bool hasElement(SET *sp, char *elt)
{
if (findElement(sp,elt) == -1) return true;
return false;
}
//finds elt and removes it from array if present, then moves all following strings forward in the array
//O(n) efficiency n=sp->size
bool removeElement(SET *sp,char *elt)
{
int loc = findElement(sp,elt);
if (loc == -1) return false;
free(sp->elts[loc]);
while (loc <sp->size)
{
sp->elts[loc] = sp->elts[loc+1];
loc++;
}
sp->size=sp->size-1;
return true;
}
函数：createSet()，
变量sp没有初始化为指向结构集的实例。
所以代码应该与此类似：
SET *sp = NULL;
if( NULL == (sp = malloc( sizeof( struct set ) ) )
{
perror( "malloc for struct set failed" );
exit( EXIT_FAILURE );
}
否则，sp将在其所在位置包含堆栈上的任何随机地址。
这是未定义的行为，可能导致seg故障事件