/*
* GETINTDRIVER -- program to call an integer reading function
*
* Compiling: put the getint function in getint.c, then say:
* gcc -ansi -pedantic -Wall -o getint getintdriver.c getint.c
*
* Usage: getint
*
* Inputs (from standard input)
* -- a line of text
* -- EOF to exit
* -- special handling of 2246, 2247, 2248, 2249
* Outputs (to standard output)
* -- a prompt when it expects input
* -- outputs indicating the success or failure of the getint call
* -- if input is integer 2246, also indicate whether getint() handles
* a NULL first argument correctly
* -- if input is integer 2247, also indicate whether getint() handles
* a NULL second argument correctly
* -- if input is integer 2248, also indicate whether getint() handles
* a NULL third argument correctly
* -- if input is integer 2249, also indicate whether getint() handles
* a NULL dereferencing of the third argument correctly
* Errors (to standard error)
* -- nothing printed
*
* Exit Code: 0
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
/*
* macros
*
* how to test for bogus arguments
*/
#define BADARG1 2246 /* if read, test handling of NULL first arg */
#define BADARG2 2247 /* if read, test handling of NULL second arg */
#define BADARG3 2248 /* if read, test handling of NULL third arg */
#define BADARG4 2249 /* if read, test handling of NULL dereference for third arg */
/*
* prototypes
*/
int getint(char *inputline, int *value, char **nextchar)
/* function to read an integer */
{
int c;
int sign;
while(isspace(c = getchar()))
;
if(!isdigit(c) && c != EOF && c != '+' && c != '-') {
**nextchar = ungetchar(c);
return 0;
}
sign = (c == '-') ? -1 : 1;
if(c == '+' || c == '-')
c = getchar();
for(*value = 0; isdigit(c); (c = getchar()))
*value = 10 * *value + (c - '0');
*value *= sign;
if(c != EOF)
ungetchar(c);
return c;
}
ungetchar(int n)
{
while(getchar() != '\n');
{
return 1;
}
}
/* {
int n;
int i;
char inpline[INT_MAX];
while(fgets(inpline, sizeof[inpline], *inputline))
{
n = antoi(inpline);
if(atoi(inpline) == 1);
{
*value = atoi(inpline);
}
else if (!atoi(inpline) && (getchar() != '\n' || inpline == '.'))
{
return 0;
}
else
{
**nextchar = inpline[n];
}
if(inpline[n] >= inpline[INT_MAX])
{
return 0;
}
else if (inpline[n] <= inpline[INT_MIN])
{
return 0;
}
return 0;
}
*/
/*
* this function calls getint with various illegal parameters
*
* Parameter: int number to trigger test (or not)
* numbers that do not trigger tests are ignored
* BADARG1 test NULL argument 1
* BADARG2 test NULL argument 2
* BADARG3 test NULL argument 3
* BADARG4 test argument 3 pointing to NULL
* Returns: nothing
* Exceptions: none
* Side Effects: prints a 1-line message identifying the test run and
* giving the success or failure of the test */
void checkargs(int testno)
{
char line[10]; /* array used for input line */
int inpnum = 0; /* space for the read number */
char *nextch = line; /* where the getint function leaves off */
int rv; /* return value from getint() */
/*
* just copy some characters into line
*/
(void) strcpy(line, "987654321");
/*
* process any magic numbers (see above)
*/
switch(testno){
case BADARG1: /* NULL first argument */
if ((rv = getint(NULL, &inpnum, &nextch)) == -1)
printf("Passed NULL first argument test\n");
else
printf("Failed NULL first argument test; returned %d\n", rv);
break;
case BADARG2: /* NULL second argument */
if ((rv = getint(line, NULL, &nextch)) == -1)
printf("Passed NULL second argument test\n");
else
printf("Failed NULL second argument test; returned %d\n", rv);
break;
case BADARG3: /* NULL third argument */
if ((rv = getint(line, &inpnum, NULL)) == -1)
printf("Passed NULL third argument test\n");
else
printf("Failed NULL third argument test; returned %d\n", rv);
break;
case BADARG4: /* NULL dereference of third argument */
nextch = NULL;
if ((rv = getint(line, &inpnum, &nextch)) == -1)
printf("Passed NULL third argument dereference test\n");
else
printf("Failed NULL third argument dereference test; returned %d\n", rv);
break;
default: /* ignore any other number */
break;
}
}
/*
* it all starts at the main routine
*/
int main(void)
{
char buf[1024]; /* input buffer */
int numread; /* number read from input */
char *nextch; /* where we left off */
int rv; /* return value of getint() */
/*
* loop until end of file
* prompting the user for an input line
*/
while(printf("> "), fgets(buf, 1024, stdin) != NULL){
/* clobber any trailing newline */
if (buf[strlen(buf) - 1] == '\n')
buf[strlen(buf) - 1] = '\0';
/*
* now process the line -- read the leading integer
* and report if it is not an integer or if
* it is too big or too small to represent
*/
switch(rv = getint(buf, &numread, &nextch)){
case -1: /* illegal parameter */
printf("Illegal call -- internal inconsistency\n");
break;
case 0: /* no leading integer */
printf("No number -- string is \"%s\"\n", nextch);
if (buf != nextch)
printf("Note -- third argument should point to first, but it doesn't\n");
break;
case 1: /* read number, all's well */
printf("Read integer %d; rest of string is \"%s\"\n", numread, nextch);
break;
case 2: /* read number but it's too big */
printf("Integer overflow (+ve) -- string is \"%s\"\n", nextch);
break;
case 3: /* read number but it's too negative */
printf("Integer underflow (-ve) -- string is \"%s\"\n", nextch);
break;
default: /* huh? should never happen */
printf("Unknown return value %d\n", rv);
break;
}
/*
* now check for illegal arguments
*/
if (rv == 1)
checkargs(numread);
}
/*
* sweet dreams ...
*/
return(0);
}
我一直收到分段错误错误，但我想要做的就是获取整数并删除非字母数字。对于这个程序，+ 123和-123是整数，而123xyz不是。 123.4不是整数，而是1234.是。但我不断收到分段错误。
更新：现在我运行它，我一直得到＆＃34;未知的返回值＃＆＃34;。过去，如果我输入一个字母，如123xys或只是字母，我得到分段错误。
答案 0 :(得分：3)
你什么时候为nextch分配内存？
char *nextch; /* where we left off */
int rv;
来自main，您正在调用方法switch(rv = getint(buf, &numread, &nextch)){
请考虑以下程序以便您理解。
#include<stdio.h>
#include<string.h>
void f(char **c){
**c = 'h';
return;
}
int main(){
char *n;
n = malloc( sizeof (char));
f(&n);
return 0;
}
如果您对该行n = malloc( sizeof (char));发表评论，则会出现细分错误。
更改您的代码，如：
char buf[1024]; /* input buffer */
int numread; /* number read from input */
char *nextch; /* where we left off */
int rv; /* return value of getint() */
nextch = malloc ( sizeof( char) * 1024);
让我知道我是否正确理解了您的问题。