malloc问题导致变量被覆盖
我的程序中有3个全局变量。由于某种原因,当我在malloc问题导致变量被覆盖,c,malloc,C,Malloc,我的程序中有3个全局变量。由于某种原因,当我在pad上运行string2bin时,binaryMessage的内容被覆盖,我不知道为什么。我增加了我的malloc的大小,但这没有帮助。我做错了什么 请注意,randomPad()创建一个随机“十六进制”值字符串,该值应转换为表示十六进制字符串的二进制字符串 char * temp; char * binaryMessage; char * pad; void process_message(char *s) int main (int arg
pad
上运行string2bin
时,binaryMessage
的内容被覆盖,我不知道为什么。我增加了我的malloc
的大小,但这没有帮助。我做错了什么
请注意,randomPad()
创建一个随机“十六进制”值字符串,该值应转换为表示十六进制字符串的二进制字符串
char * temp;
char * binaryMessage;
char * pad;
void process_message(char *s)
int main (int argc, const char * argv[]) {
temp = (char *)malloc(sizeof(char *) *2048);
binaryMessage = (char *)malloc(sizeof(char *) *2048);
pad = (char *)malloc(sizeof(char *) * 2048);
process_message("test");
}
char * char2bin ( unsigned char c ){
static char bin[CHAR_BIT + 1] = {0};
int i;
for ( i = CHAR_BIT - 1; i >= 0; i-- ) {
bin[i] = (c % 2) + '0';
c /= 2;
}
return bin;
}
char* string2bin(char* str){
int i;
int len = strlen(str);
sprintf(temp,"");
for(i=0; i< len;i++){
sprintf(temp, "%s%s",temp,char2bin(str[i]));
}
return temp;
}
char* randomPad(){
int i;
const char *hex_digits = "0123456789ABCDEF";
char * p = (char*)malloc(sizeof(char*)*242);
// clear old pad data
//sprintf(pad,"");
// create random string of 242 hex chars to use as pad
for(i = 0; i< 242; i++){
sprintf(p,"%s%c",p,hex_digits[ ( rand() % 16 ) ]);
}
return p;
}
void process_message(char *s){
binaryMessage = string2bin(s);
printf("m %s\nbm %s\n",s, binaryMessage);
//get random one time pad
pad = string2bin(randomPad());
printf("m %s\nbm %s\n",s, binaryMessage);
}
我的实际产出是:
m test
bm 01110100011001010111001101110100
m test
bm 01110100011001010111001101110100
m test
bm 01110100011001010111001101110100
m test
bm 0011011100110001001110010100000100110010001110000011100001000101001100110100010000111000001101010100001100110010001100110011011100110111001100010011100000110100010001100011000101000100001101010011100000110101010000100011011000111000001101110011100100110010001110000011001100110010001100010011001101000100001100110011010101000110001100000011000100111000010001000011000101000011010000100011001000110101001110010011000100110100001110000011010000110010010000110011010001000001001101110100000101000001001101010011100000111001001101010011000100110000001101000011010101000001001101010100001001000100001110010011011000110111001110000011000100110101001100110100010101000100001101010011010100110011001110010011010001000010010000010100001100110011001100010011001000110000010001010100001100110001001101100011100001000100001100010100011000110100001100010100010100111001010001000011011000110000001110010011011100110001010001100011001101000001010001010100011000110000010000110011010000110101010000010011100001000010001100000011100100110010010001010011001000110110001101010011001001000011010001100100010001000110001110000011011101000100010001010100011000110010001100010011000001000101001110000011011100110111010001010011010000110010001101110011011101000101001101110011000100111000001110010100010101000010001100100011010100110010001101100011011001000011001101000100010100110110010000010011001000110011001100100011010000110110001101100011011101000110001100110011100100110001001110000011001101000110001100010011100000110101010001100011010000110000001100000011011101000010001110010100010101000001010000100011011100111000010000110100011000110010010000110100001100110111010001100011000101000100001101010011000100110011001100010100000101000101001100110011000000110001001110010011000100110111010000110100001000111000010001100100011000110010001100110100001101000100001110000011000001000101001110000100001001000100010001100100011000110001001100010011000001000110
以下几点至关重要:
sprintf(temp, "%s%s", temp, char2bin(str[i]));
...
sprintf(p, "%s%c", p, hex_digits[ ( rand() % 16 ) ]);
发件人:
有些程序轻率地依赖如下代码
将文本附加到buf。但是,标准明确指出,如果在调用sprintf()、snprintf()、vsprintf()和
vsnprintf()。根据所使用的gcc(1)版本和所使用的编译器选项,上述调用不会产生预期结果
以下几点至关重要:
sprintf(temp, "%s%s", temp, char2bin(str[i]));
...
sprintf(p, "%s%c", p, hex_digits[ ( rand() % 16 ) ]);
发件人:
有些程序轻率地依赖如下代码
将文本附加到buf。但是,标准明确指出,如果在调用sprintf()、snprintf()、vsprintf()和
vsnprintf()。根据所使用的gcc(1)版本和所使用的编译器选项,上述调用不会产生预期结果
除了alk指出的错误之外,您还有四个问题 1-这是:
char * p = (char*)malloc(sizeof(char*)*242);
应该是这样的:
char * p = malloc(sizeof(char)*243); // Do NOT cast malloc
sprintf(p+i,"%c",hex_digits[ ( rand() % 16 ) ]);
2-这是:
sprintf(p,"%s%c", p, hex_digits[ ( rand() % 16 ) ]);
应该是这样的:
char * p = malloc(sizeof(char)*243); // Do NOT cast malloc
sprintf(p+i,"%c",hex_digits[ ( rand() % 16 ) ]);
3-你错过了这个:
*(p+242) = '\0';
return p;
4-最后,这一行代码:
binaryMessage = string2bin(s);
将binaryMessage
指针替换为temp
指针值
我能提供的最好建议是什么?除掉所有的地球人。你需要在随机数生成器中植入一些不可预测的东西(例如,当前时间),否则每次都会得到相同的“随机”数序列。除了alk指出的错误,你还有四个问题 1-这是:
char * p = (char*)malloc(sizeof(char*)*242);
应该是这样的:
char * p = malloc(sizeof(char)*243); // Do NOT cast malloc
sprintf(p+i,"%c",hex_digits[ ( rand() % 16 ) ]);
2-这是:
sprintf(p,"%s%c", p, hex_digits[ ( rand() % 16 ) ]);
应该是这样的:
char * p = malloc(sizeof(char)*243); // Do NOT cast malloc
sprintf(p+i,"%c",hex_digits[ ( rand() % 16 ) ]);
3-你错过了这个:
*(p+242) = '\0';
return p;
4-最后,这一行代码:
binaryMessage = string2bin(s);
将binaryMessage
指针替换为temp
指针值
我能提供的最好建议是什么?除掉所有的地球人。您需要在随机数生成器中植入一些不可预测的内容(例如,当前时间),否则每次都会得到相同的“随机”数序列。
randomPad
生成一个242位的字符串。为什么希望字符串更短?没错,应该输出。我在运行randomPad()前后打印binaryMessage
binaryMessage
应该保持不变,但它完全不同。randomPad
生成一个242位的字符串。为什么希望字符串更短?没错,应该输出。我在运行randomPad()前后打印binaryMessage
binaryMessage
应该是不变的,但它是完全不同的。这行char*p=(char*)malloc(sizeof(char*)*)*…
应该是char*p=malloc(sizeof(char)*…
或者更灵活char*p=malloc(sizeof(*p)*…
char
与char*
不同。这是一个很好的捕捉。编辑以反映变化。而且sizeof(char)
是1
所以你可以完全摆脱它。@mattmcnab是真的,但我认为sizeof(char)*243
比单纯的243
更能显示意图。当然,用命名常量替换幻数是最好的。这一行char*p=(char*)malloc(sizeof(char*)*)*…
应该是char*p=malloc(sizeof(char)*…
或者更灵活的char p=malloc sizeof(*p)*…
char
与char*
不同。这是一个很好的捕捉。编辑以反映变化。而且sizeof(char)
是1
所以你可以完全摆脱它。@mattmcnab是真的,但我认为sizeof(char)*243
比243
更能显示意图。当然,用命名常量替换幻数是最好的。