段錯誤調用結構

Question

對不起，如果這已經被問過無數次，但我想我已經理解的字符串（字符數組）如何在C

工作，在我的程序有問題，我的成員時「堆棧」結構，它看起來像這樣（在stack.h）：

struct stack_t { 
/* Stack-Datentyp */ 
/* Stacks have a head-node, a length, and a name. 
Stacks are filled with links (nodes) that are defined below. These links have 
a generic data pointer and a pointer to the next link */ 
link head;      
unsigned int length;    
char *name;      //stack name 
}; 

typedef struct stack_t *stack; 

在我的main.c

，我稱之爲叫「stack_new」功能，這似乎正常工作，因爲所有的printf通話工作：

stack stack_new(char *stackname) { 
    /* creates a new, empty stack */ 
stack st = (stack)(malloc(sizeof(stack))); 
if (st == NULL) { 
fprintf(stderr, "Error: Memory for Stack could not be allocated!\n"); 
return NULL; 
} 
st->head = NULL; 
printf("head works.\n"); 
st->length = 0; 
printf("length works.\n"); 
st->name = stackname; 
printf("stackname works.\n"); 
return st; 
} 

現在，當我在main.c中調用此函數時，出現seg故障。這是電話：

if (strcmp(input,"newstack") == 0) { 
    printf("Please enter stackname:\n"); 
    scanf("%s", &stackname); 
    printf("Debug: Input works.\n"); 
    stacklist[NumberOfStacks] = stack_new(stackname); 
    printf("stack created works-\n"); 
    NumberOfStacks++; 
    printf("A new stack with the name '%s' was created!\nIt is number %d in stack list.", stacklist[NumberOfStacks]->name, NumberOfStacks); 
    continue; 
} 

當我嘗試打印struct stacklist [NumberOfStacks]指向的成員名稱時發生seg故障。我在這裏做錯了什麼？

我還弄了一堆，告訴我關於我的stackname scanf的期望如何不同類型的警告：

警告：格式「％s」的期望類型的參數「字符」，但爭論2 'char（）[50]'[-Wformat =] scanf（「％s」，& stackname）;

我得到的其他警告告訴我，我沒有從我用於堆棧節點中的數據存儲的虛空指針中進行類型轉換，但我不認爲這與我的問題有關。

謝謝你的幫助！

編輯： 問題是我在將NumberOfStacks用作打印保存在數組中的結構成員的索引之前遞增了NumberOfStacks。

NumberOfStacks++; 
    printf("A new stack with the name '%s' was created!\nIt is  number %d in stack list.", stacklist[NumberOfStacks]->name, NumberOfStacks); 

這部分程序現在工作正常，謝謝！

Answer 1

代碼中有幾個錯誤。評論中大多數都已經提到。我做了更正，似乎沒有段錯誤。 修改通過代碼中的註釋表示。

這是我結束了的代碼：

#include <stdio.h> 
// Prototype for malloc 
#include <stdlib.h> 
// Prototype for strdup 
#include <string.h> 

typedef void *link; /* Added to make it compile - you may have a different definition in your code */ 

struct stack_t { 
    /* Stack-Datentyp */ 
    /* Stacks have a head-node, a length, and a name. 
    * Stacks are filled with links (nodes) that are defined below. 
    * These links have 
    * a generic data pointer and a pointer to the next link */ 
    link head; 
    unsigned int length; 
    char *name;      //stack name 
}; 

typedef struct stack_t *stack; 

stack stack_new(char *stackname) { 
    /* creates a new, empty stack */ 
    stack st = malloc(sizeof(*st)); // changed to use the variable name 
    if (st == NULL) { 
     fprintf(stderr, "Error: Memory for Stack could not be allocated!\n"); 
     return NULL; 
    } 
    st->head = NULL; 
    printf("head works.\n"); 
    st->length = 0; 
    printf("length works.\n"); 
    st->name = strdup(stackname); // Changed: Duplicate the name so it won't get overwritten when creating the next stack 
    printf("stackname works.\n"); 
    return st; 
} 


int main(void) 
{ 
    char stackname[50];  // Added declaration for stackname. 
    stack stacklist[50];  // Added declaration. Can handle up to 50 stacks. 
    int NumberOfStacks = 0; 

    printf("Please enter stackname:\n"); 
    scanf("%s", stackname);    // Changed. Removed the "&" since stackname is a char*. 
    printf("Debug: Input works.\n"); 
    stacklist[NumberOfStacks] = stack_new(stackname); 
    printf("stack created works-\n"); 
    // All data is at index 0, so cannot use increased value of NumberOfStacks to get get the data. Also changed the text to "has index" since a 0 will be printed for stacknumber. 
    printf("A new stack with the name '%s' was created!\nIt has index %d in stack list.\n", stacklist[NumberOfStacks]->name, NumberOfStacks); 
    NumberOfStacks++; // Moved this line down. 
    return 0; 
} 

Answer 2

對於警告，scanf正在等待類型'指向char'的指針。你的變量'stackname'被聲明爲'char stackname [50]'（我想你沒有發佈聲明）。 使用& stackname表示您想訪問數組的地址。使用堆棧名或堆棧名幾乎相同，因爲在第一種情況下，數組將被轉換爲指向數組的第一種情況的指針，在第二種情況下，它將是數組的地址，這是第一種情況的陣列。

如果你想複製一個字符串，你必須分配一個字符串大小的緩衝區（使用malloc）並使用strcpy。

對於段錯誤，向我們展示stacklist和NumberOfStacks的聲明。原因可能是NumberOfStacks的值大於數組的大小。