从二进制文件读取数据并将其存储在结构中会产生分段错误
我遇到了“分段错误”错误。
我正在从二进制文件读取数据，我试图将其存储在结构中；这是我正在做或“尝试”做的事情的代码：
struct Medico //users are medics
{
int Id_Doctor; //Id User
int Estado; //status of the user
char Nombre[60]; //name of the user
char Clave_Acceso[20]; //password of the user
char Especialidad[40]; //especialty of the user
struct Medico *next;
};
void Cargar_Datos () //load files
{
FILE *Archivaldo; ///file- Archivo means file
struct Medico * head = NULL;
struct Medico * prev, *current;
char especialida[40], password[20]; ///locals for specialty and password
char nombre_doc[60]; ///local for name
int estado_doc, id_doc; // local for status
if((Archivaldo=fopen("md.dat", "a+b"))==NULL)
{
printf("No se pudo abrir el archivo de Medicos\n");
exit(1);
}
rewind(Archivaldo);
current = (struct Medico *) malloc (sizeof(struct Medico));
fread(&id_doc, sizeof(int), 1, Archivaldo);
fread(nombre_doc, sizeof(char), sizeof(nombre_doc), Archivaldo);
fread(password, sizeof(char), 20 , Archivaldo);
fread(especialida, sizeof(char), 40, Archivaldo);
fread(&estado_doc, sizeof(int), 1, Archivaldo);
printf("ID: %d\n", id_doc);
printf("\nDoctor: ");
puts(nombre_doc);
printf("\nPassword: ");
puts(password);
printf("\nEspecialidad: ");
puts(especialida);
printf("\nEstado: ");
if(estado_doc==1)
puts("Activo\n");
else
puts("Inactivo\n");
current->Id_Doctor=id_doc;
strcpy(current->Nombre, nombre_doc);
strcpy(current->Clave_Acceso, password);
strcpy(current->Especialidad, especialida);
current->Estado=estado_doc;
current=current->next;
fclose(Archivaldo);
}
I'm having problems with a 'segmentation fault' error.
I'm reading data from a binary file, which I'm trying to store in a structure; here's the code to what I'm doing or 'trying' to do:
struct Medico //users are medics
{
int Id_Doctor; //Id User
int Estado; //status of the user
char Nombre[60]; //name of the user
char Clave_Acceso[20]; //password of the user
char Especialidad[40]; //especialty of the user
struct Medico *next;
};
void Cargar_Datos () //load files
{
FILE *Archivaldo; ///file- Archivo means file
struct Medico * head = NULL;
struct Medico * prev, *current;
char especialida[40], password[20]; ///locals for specialty and password
char nombre_doc[60]; ///local for name
int estado_doc, id_doc; // local for status
if((Archivaldo=fopen("md.dat", "a+b"))==NULL)
{
printf("No se pudo abrir el archivo de Medicos\n");
exit(1);
}
rewind(Archivaldo);
current = (struct Medico *) malloc (sizeof(struct Medico));
fread(&id_doc, sizeof(int), 1, Archivaldo);
fread(nombre_doc, sizeof(char), sizeof(nombre_doc), Archivaldo);
fread(password, sizeof(char), 20 , Archivaldo);
fread(especialida, sizeof(char), 40, Archivaldo);
fread(&estado_doc, sizeof(int), 1, Archivaldo);
printf("ID: %d\n", id_doc);
printf("\nDoctor: ");
puts(nombre_doc);
printf("\nPassword: ");
puts(password);
printf("\nEspecialidad: ");
puts(especialida);
printf("\nEstado: ");
if(estado_doc==1)
puts("Activo\n");
else
puts("Inactivo\n");
current->Id_Doctor=id_doc;
strcpy(current->Nombre, nombre_doc);
strcpy(current->Clave_Acceso, password);
strcpy(current->Especialidad, especialida);
current->Estado=estado_doc;
current=current->next;
fclose(Archivaldo);
}
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您正在使用
fread读取nombre_doc、especialida和所有其他字符串。这很好，但它不会以'\0'字符终止字符串。您使用 puts 和 strcpy ，它们期望这些字符串以 nul 终止符结尾。首先，将字符串的大小增加 1。然后终止字符串：
You are reading
nombre_doc,especialidaand all other strings withfread. This is fine but it does not terminate the strings with a'\0'character. You useputsandstrcpywhich are expecting these strings to end with the nul-terminator.First, increase the size of the strings with 1. After that terminate your strings:
调试分段错误的最佳方法是使用 GDB 等调试器或 Valgrind 等内存分析器。
如果没有，通常可以在代码中添加编号的 printf() 语句。当您找到错误之前执行的最后一个 printf() 时，您可以添加更多 printf() 语句并重复测试以缩小范围。
C 程序中分段错误的一些常见原因：
尝试取消引用 NULL 指针。如果所述指针是诸如 malloc() 或 fopen() 之类的函数调用的结果，而在继续之前未检查其输出是否有错误，则经常会发生这种情况。
超出数组或分配块的边缘。未正确以 null 终止的字符串是造成这种情况的常见原因。如果打印字符串在屏幕上产生垃圾，这可能就是原因。
尝试使用已通过 free() 释放的内存块。
The best way to debug a segmentation fault is to use a debugger such as GDB or a memory analyser such as Valgrind.
If one is not available, it usually helps to add numbered printf() statements in the code. When you find the last printf() that was executed before the error, you can add more printf() statements and repeat your tests to narrow it down.
A few common causes of a segmentation fault in C program:
Trying to dereference a NULL pointer. That often happens if said pointer is the result of a function call such as malloc() or fopen(), whose output was not checked for errors before proceeding.
Going beyond the edges of an array or allocated block. Strings that are not null-terminated properly are a common cause of this. If printing a string produces garbage in the screen, this could be the cause.
Trying to use a memory block that has already been freed with free().