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我一直在寫C約一個星期，所以請耐心等待。我在方法assemble_url中遇到了分段錯誤錯誤，我不知道爲什麼。這裏是我的代碼：使用結構012的seg故障
/** Includes */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mysql/mysql.h>
/** Definitions */
#define MAX_OPTIONS 32
#define MAX_ARGS 32
/** Command option */
typedef struct {
char *argname;
char *value;
} command_option;
/** Command */
typedef struct {
command_option options[MAX_OPTIONS];
} command_t;
/**
* Prints the arguments passed in in a hashmap format (key => value)
*/
void populate_command(command_t *cmd,int argc,char *argv[])
{
int i,j=0;
/** Check to see if we have arguments. If argc is equal to 1 than there are no arguments besides the filename */
if(argc>1)
{
/* Start at position 1, since argv[0] is the filename being called */
for(i=1;i<argc;i++)
{
/* Head of argv array */
char *arg = argv[i];
/* Create a copy of head for traversal. */
char *c = arg;
/* traverse the char array, ensuring we arent dealing with NULL values(c!==NULL) and NULL pointers(*c!=='\0') */
while(*c != '\0' && c != NULL)
{
/* Were only concerned with parsing the flags and obtaining the flag value. */
if(strchr("-",*c))
{
char *key = c; /* Key */
char *value = argv[i+1]; /* Value */
/* ensure we have a value existent for key */
if(strchr("-",*value))
{
/** user supplied a key with no value */
break;
}
command_option *option = &cmd->options[j];
option->argname = key;
option->value = value;
j++;
/* Debug dump */
printf("arg %d: %s -> %s\n",i,option->argname,option->value);
}/* end strchr */
/** Increment the traversal array */
c++;
}/* end while loop */
}/* end forloop */
}/* endif */
}/** end print_args */
/**
* Concatenates two strings and returns the resulting concatenated string
*/
char* concatstring(char *s1,char *s2)
{
/* Allocate memory for *result. We add 1 to account for the extra byte to store the null character. Strlen accounts for all
non-null bytes, so using strlen(s1) + strlen(s2) + 1 ensures that an overflow wont occur. An overflow occurs when
the number of bytes being used (in our example, is the addition of strlen for s1 and s2) is more than the number of bytes
allocated (in our example, the number of bytes allocated to *result)*/
char *result = malloc(strlen(s1)+strlen(s2)+1);
/*Copies the C string pointed by source(s1) into the array pointed by destination(result), including the terminating null character. */
strcpy(result,s1);
/* appends a copy of the source string(s2) to the destination string(result). The terminating null character in
destination is overwritten by the first character of source, and a null-character is included at
the end of the new string formed by the concatenation of both in destination.*/
strcat(result,s2);
/* return result */
return result;
} /** end concatstring */
char* assemble_url(command_t *cmd,char *str)
{
int i,opt_len = sizeof(&cmd->options);
for(i=0;i<opt_len;i++)
{
command_option *option = &cmd->options[i];
char *key = option->argname;
char *value = option->value;
if(i==0)
{
str = concatstring(str,key);
str = concatstring(str,"=");
str = concatstring(str,value);
}
else
{
str = concatstring(str,"&");
str = concatstring(str,key);
str = concatstring(str,"=");
str = concatstring(str,value);
}
}
return str;
}
在這個程序中出現什麼如下：
1.在程序名稱和標誌選項/用戶類型，如下列： program -test a -test2 b
2。 /程序解析命令並用選項填充命令結構體。每個選項都有與之相關聯的（值）
3. /程序然後試圖創建與這些選項鍵和值的URL的標誌（argname）和值，諸如http://url/?test=a&test2=b
程序編譯，但我對於指針和引用（我認爲&被稱爲引用）還是新的，所以也許這就是程序錯誤的原因。
任何幫助，非常感謝！另外，如果你看到任何探針或更好的方式來處理assemble_url，請讓我知道（我不認爲它被以最好的方式處理，但就像我說的，我對C編程非常陌生）
謝謝！
現在是學習如何的好時機使用調試器。它將幫助您查明崩潰的位置，讓您檢查函數調用堆棧，並讓您檢查變量以幫助您找出崩潰的可能原因。 –
你知道這個代碼泄漏了多少內存嗎？鏈接的'str = concatstring（str，...）'電話可能是你想要考慮重新考慮的事情，等等。 – WhozCraig
我更新了內容。該程序編譯通過取消註釋assemble_url。我不確定如何使用調試器。 – jkushner