檢測到C堆棧粉碎

Question

我有一個函數可以計算一個文件出現在單詞上的次數。現在由於某種原因，它得到堆棧粉碎檢測到的錯誤，我沒有看到錯誤。

下面是代碼：

int contar_palabra(const char *nombre_file, const char *palabra){ 

/*variables locales*/ 
FILE *file; 
char buffer[50]; 
int bytes_leidos, contador = 0, comparar, cerrar, i;  

/*Abrimos el archivo para lectura*/ 
file = fopen(nombre_file, "r"); 

/*Verificamos que se haya abierto correctamente*/ 
if (file == NULL){ 
    printf("No se pudo abrir el archivo \n"); 
    perror(nombre_file); 
    exit(EXIT_FAILURE); 
} 

/*Procedemos a contar cuantas veces aparece una palabra*/ 
while (!feof(file)){ 

    bytes_leidos = fscanf(file, "%s", buffer); 

    if (bytes_leidos > 0){ 

    /*Hacemos la comparacion*/ 
    comparar = strcmp(buffer, palabra); 
    if (comparar == 0) 
     contador++; 
    } 
    else if(errno == EOF)  
     printf("Error al leer alguna palabra de %s \n", nombre_file); 
    else if (bytes_leidos == EOF) 
    break; 
} 

cerrar = fclose(file); 

if(cerrar == EOF){ 
    printf("Error: no se pudo cerra el archivo."); 
} 

printf("antes de retornar contador \n"); 
return contador; 

}

我使用的valgrind試圖找出錯誤，和日誌文件給了我這個：

==2252== Memcheck, a memory error detector 
    ==2252== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al. 
    ==2252== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info 
    ==2252== Command: ./pargrep viejo.txt 
    ==2252== Parent PID: 1756 
    ==2252== 
    ==2252== 
    ==2252== HEAP SUMMARY: 
    ==2252==  in use at exit: 55 bytes in 1 blocks 
    ==2252== total heap usage: 7 allocs, 6 frees, 1,389 bytes allocated 
    ==2252== 
    ==2252== 55 bytes in 1 blocks are still reachable in loss record 1 of 1 
    ==2252== at 0x4026864: malloc (vg_replace_malloc.c:236) 
    ==2252== by 0x40B878B: __libc_message (libc_fatal.c:138) 
    ==2252== by 0x413D09F: __fortify_fail (fortify_fail.c:32) 
    ==2252== by 0x413D049: __stack_chk_fail (stack_chk_fail.c:29) 
    ==2252== by 0x8049142: contar_palabra (in /home/alessandro/OS/Proyecto2/prueba1.0/pargrep) 
    ==2252== by 0x80489D4: main (in /home/alessandro/OS/Proyecto2/prueba1.0/pargrep) 
    ==2252== 
    ==2252== LEAK SUMMARY: 
    ==2252== definitely lost: 0 bytes in 0 blocks 
    ==2252== indirectly lost: 0 bytes in 0 blocks 
    ==2252==  possibly lost: 0 bytes in 0 blocks 
    ==2252== still reachable: 55 bytes in 1 blocks 
    ==2252==   suppressed: 0 bytes in 0 blocks 
    ==2252== 
    ==2252== For counts of detected and suppressed errors, rerun with: -v 
    ==2252== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 15 from 8) 

請告訴我奇怪的是，它在返回之前打印消息。 我真的沒有看到錯誤，欣賞幫助。 由於事先

Answer 1

使用普通%s作爲格式說明fscanf是非常危險的，因爲你必須超越這是在你的情況下，只有50個字節的緩衝區結束對寫作沒有保護。考慮爲格式說明符提供一個寬度修飾符，但是當寬度限制達到更復雜時，這將處理精確的計數。

您可能會發現，逐個字符（fgetc）或讀取固定緩衝區（fread）以及手動檢測分隔符會產生更簡單的代碼。