全局變量

Question

意想不到的初始化我有頭文件爲：

test.h

//Mandatory fields size macro 
#define size_uid 65 
#define size_txn 33 
#define size_adhaarNo 13 
#define size_ver 4 
#define size_input 65 
#define size_photo 1024*1024*10 
#define size_pseudonym 50 
#define size_name 50 

//Mandatory fields declaration 
char uid[size_uid]; 
char txn[size_txn]; 
char adhaarNo[size_adhaarNo]; 
char ver [size_ver]; 
char *photo; 
char pseudonym[size_pseudonym]; 
char name[size_name]; 
char input[size_input]; 
void incorrect_val_test(FILE *, FILE *, FILE *, FILE *, FILE *, FILE *,FILE *,FILE *,FILE *,FILE*); 

test.c的

#include "test.h" 

//Mandatory fields declaration 
char uid[] = "865A80A01C70A9E0D5FC5F4D354A9155BF58CD483B1397C92614E5BC92317ACC"; 
char txn[] = "23da7b99-c561-4102-9df8-d37fbfe1"; 
char adhaarNo[] = "250241800087"; 
char ver [] = "1.0"; 
char *photo = (char *)malloc(sizeof(char)*size_photo); 
char pseudonym[] = "2b6c55566d14459991513fb00bce34ed"; 
char name[] = "Amarjeet Sharma"; 
char input[] = "936a185caaa266bb9cbe981e9e05cb78cd732b0b3280eb944412bb6f8f8f07af"; 

void incorrect_val_test(FILE *ver, FILE *ts, FILE *txn, FILE *vtxn, FILE *uid, FILE *input, FILE *adhaarNo, FILE *photo, FILE *name, FILE *pseudonym) 
{ 
     //Some initialization and files are opened here.... 

    photo = (char *)malloc(sizeof(char)*size_photo); 

    FILE *photos = fopen("./input/data.txt","r"); 

    if(photos == NULL) 
    { 
     printf("Can't open data file.\n"); 
     return; 
    } 

    i=0; 

    while((read_char = fgetc(photos))!= EOF) 
    { 
     if(read_char == '\n') 
     continue; 

     photo[i]= read_char; 
     i++;  
    } 


// Some more processing done here 
} 

的main.c

int main() 
{ 

     // Some files are opened here to read data. 
     incorrect_val_test(fp_ver, fp_ts, fp_txn, fp_vtxn, fp_uid, fp_input, fp_adhaarNo, fp_photo, fp_name, fp_pseudonym); 

     return 0; 
} 

當我編譯它提供了以下錯誤消息

錯誤信息

warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
photo = (char *)malloc(sizeof(char)*size_photo);
error: incompatible types when assigning to type ‘FILE {aka struct _IO_FILE}’ from type ‘char’
photo[i]= read_char;

有人能指出我在哪裏，我錯了？

Answer 1

你具備的功能

void incorrect_val_test(..., FILE *photo, ...) 

注意，你有一種說法認爲陰影全局變量。這是你的錯誤的原因。

Answer 2

你可以有一個函數調用像

char *photo = (char *)malloc(sizeof(char)*size_photo); 

一個功能內。這是不允許在全球範圍內。刪除全球一，留下incorrect_val_test()函數內的一個。

此外，請do not cast返回值malloc()和家庭在C。

解決方案：

1. 在全球範圍內定義char *photo = NULL;。

2. 當你這樣做，分配內存以photo您incorrect_val_test()裏面，像

   char *photo = malloc(size_photo); //cast not required 
               // sizeof(char) is guranteed to be 1 
   

然後，在你的函數參數列表

void incorrect_val_test(..., FILE *photo, ...) 

了 FILE *photo在 incorrect_val_test()功能

這影響了全球char * photo。

恕我直言，你想要的是寫

void incorrect_val_test(..., FILE *photos, ...) 
             ^
             | 

，並在函數體中，

photos = fopen("./input/data.txt","r"); 

但是，那麼，爲什麼要使用的變量名以單個字符的區別？使用更詳細和容易區分的內容。

注意：在完成使用photo後，請不要忘記爲free()分配內存以避免內存泄漏。