美好的一天！我有这个软件加密和解密文件。我不熟悉实时操作系统，因为我通常编程微控制器，我在不久前编写了Operatins系统的基本内容，包括这个项目。 Codeblocks gnu C便携式编译器IDE告诉我没有错误只有警告。但是当我执行代码时，它会运行到某个点，然后给出程序意外停止并且命令提示符需要关闭的错误。
代码和警告在这里。从命令提示符我得到：Process returned 255 0xFF。也许变量定义需要超过8位。
#include <stdio.h>
#include <stdlib.h>
void main ()
{
char *f1;
char *f2;
printf ("Please enter file for encryption\n");
scanf ("%s", f1);
printf ("Please enter the name of the file after encryption\n");
scanf ("%s", f2);
Encrypt(f1, f2);
}
int Encrypt(char * FILENAME, char * NEW_FILENAME)
{ /********VARIABLE DEFINITION BLOCK*******/
printf("Encryption started\n");
FILE *inFile; //Declare inFile
FILE *outFile; //Declare outFile
char *key;
char *process;
char Byte;
char newByte;
/*int n;*/
/******USER INPUT BLOCK*******/
printf ("Please enter 'encryption or decryption'\n");
scanf ("%s", process);
printf ("Please enter the key\n");
scanf ("%s", key);
printf("Opening files\n");
/*int i=0;*/
/******FILE OPEN BLOCK********/
inFile = fopen(FILENAME,"rb");
outFile = fopen(NEW_FILENAME, "w");
/*****MAIN PROGRAM BLOCK******/
if(inFile == NULL) /* check if the input file is empy */
{
printf("Error: Can't Open inFile\n");
}
/* check if the output file is empty */
if(outFile == NULL)
{
printf("Error: Can't open outFile\n");
}
/* if both files are not empty output "Encrypting" and begin encryption */
else
{
printf("File Opened, Encrypting\n");
/* encrypting cycle */
while(1)
{
printf("."); /* loading symbol */
/* if the current byte is not the "End of file" byte and the process is encryption */
if(Byte!=EOF && process == 1)
{ /* Byte = function get char from "inFile" */
Byte = fgetc (inFile);
// printf("%d",Byte); /* the new byte = old byte plus 1 byte from the key */
newByte = Byte + key;
/* we put the new byte in the new already encrypted file */
fputc(newByte, outFile);
}
/* if the current file is not the "End of file" byte and the process is decryption */
if(Byte!=EOF && process == 2)
{ /* we read 1 byte with the function get char from the file recorded in the string (pointer) "inFile */
Byte = fgetc (inFile);
// printf("%d",Byte); /* 1 new byte, equals the old byte plus 1 byte from the key */
newByte = Byte + key;
/* we put the new byte with the function put char in the string (pointer) in which the output file is */
fputc(newByte, outFile);
}
/* if the two "while conditions" are not true we print "End of file" */
else
{
printf("End of File\n");
}
return 1;
}
}
}
构建输出：
||=== Build: Debug in Encryption-software (compiler: GNU GCC Compiler) ===|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|7|warning: return type of 'main' is not 'int' [-Wmain]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'main':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|17|warning: implicit declaration of function 'Encrypt' [-Wimplicit-function-declaration]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'Encrypt':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|65|warning: comparison between pointer and integer|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|69|warning: assignment makes integer from pointer without a cast|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|75|warning: comparison between pointer and integer|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|79|warning: assignment makes integer from pointer without a cast|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|92|warning: control reaches end of non-void function [-Wreturn-type]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|34|warning: 'process' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|36|warning: 'key' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|65|warning: 'Byte' may be used uninitialized in this function [-Wmaybe-uninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c||In function 'main':|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|13|warning: 'f1' is used uninitialized in this function [-Wuninitialized]|
C:\Users\arakel-the-dragon\Documents\Encryption-software\main.c|15|warning: 'f2' is used uninitialized in this function [-Wuninitialized]|
||=== Build finished: 0 error(s), 12 warning(s) (0 minute(s), 1 second(s)) ===|
答案 0 :(得分：2)
首先，让我们解决警告。
有几个警告是使用未初始化的变量。其中每个都涉及将char *传递给scanf。 %s的{{1}}格式说明符需要指向字符数组的指针。你传入的是一个指向任何地方的指针。取消引用未初始化的指针会调用undefined behavior，在这种情况下会显示为崩溃。
将这些变量声明为scanf数组，并为您期望的输入提供足够的空间。另外，将长度说明符添加到char，指定要读取的最大字符数。
整数/指针比较错误是因为您使用%s的方式。这个变量是process，期望指向一个以空字符结尾的字符串，但是你要将它与一个没有意义的整数进行比较。
相反，请使用char *功能将其与strcmp或"encryption"进行比较。
＆＃34;赋值在没有强制转换的情况下从指针生成整数＆＃34;是因为您尝试将"decryption" key添加到char *，这是Byte。您可能希望将char编入索引以从中获取特定字符，即key。您还需要一个单独的计数器用于当前密钥索引，并且当它变得大于或等于密钥长度时，您希望将其重置为0.
第一次进入key[1]循环时，while尚未设置，但您仍然会将其与Byte进行比较。当您在下一个字节中读取时，您还会覆盖EOF的比较值，但是您不会检查它是否为Byte。
您需要将EOF和Byte的类型更改为newByte，因为int返回的是fgetc。 EOF值通常超出char的范围，因此除非您更改类型，否则您永远不会找到它。您还应该执行读取和比较作为循环条件的一部分，而不是使用while(1)并从循环体中删除读取。
隐式声明警告是因为在定义或声明它之前调用Encrypt函数。结果，创建了int Encrypt()的隐式声明（即，获取未知数量的参数并返回int的函数）。这恰好与它的定义方式一致，但仍然不匹配。
在main之前为此函数添加声明，或在main之前移动整个函数。
除了警告之外，return 1语句在while循环的底部执行，因此循环在退出之前只进行一次迭代。以上建议在条件中测试Byte的值应该解决这个问题。
您的解密目前与加密相同。你可能想在这里减去而不是添加。在这两种情况下，您还需要检查环绕性。因此，如果加密值大于255，则减去256.对于解密，如果值小于0，则添加256。
应用这些修补程序后，您的代码应如下所示：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// declare function before it's called
void Encrypt(char * FILENAME, char * NEW_FILENAME);
int main ()
{
char f1[100]; // array big enough to hold expected input
char f2[100]; // array big enough to hold expected input
printf ("Please enter file for encryption\n");
scanf ("%99s", f1); // set max characters to read to prevent buffer overflow
printf ("Please enter the name of the file after encryption\n");
scanf ("%99s", f2);
Encrypt(f1, f2);
return 0;
}
void Encrypt(char * FILENAME, char * NEW_FILENAME)
{
printf("Encryption started\n");
FILE *inFile;
FILE *outFile;
char key[50]; // array big enough to hold expected input
char process[50]; // array big enough to hold expected input
int keylen, keyidx;
int Byte; // fgetc returns int, so use an int
int newByte;
printf ("Please enter 'encryption or decryption'\n");
scanf ("%49s", process);
printf ("Please enter the key\n");
scanf ("%49s", key);
keylen = strlen(key);
keyidx = 0; // starting index into key
printf("Opening files\n");
inFile = fopen(FILENAME,"rb");
outFile = fopen(NEW_FILENAME, "w");
if(inFile == NULL)
{
printf("Error: Can't Open inFile\n");
}
else if(outFile == NULL)
{
printf("Error: Can't open outFile\n");
}
else
{
printf("File Opened, Encrypting\n");
while((Byte = fgetc(inFile)) != EOF) // read a byte, check if EOF
{
if (!strcmp(process,"encryption"))
{
newByte = Byte + key[keyidx]; // use key index
if (newByte > 255) newByte -= 256; // check for overflow
}
else if (!strcmp(process,"decryption"))
{
newByte = Byte - key[keyidx];
if (newByte < 0) newByte += 256;
}
else
{
newByte = Byte;
}
fputc(newByte, outFile);
keyidx++;
// loop to the start of the key if needed
if (keyidx >= keylen) keyidx = 0;
}
}
if (inFile != null) fclose(inFile); // close your files when you're done
if (outFile != null) fclose(outFile);
}