C 修改全局字符数组

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我在 C 语言中遇到问题。我想在 function1 中更新/修改全局字符串(字符数组)

如何更新变量 dest 并与 main 函数共享？

编辑:我找到了解决方案

char *alphabet;

int function1(char* newstring) {


    alphabet = (char*)malloc(63);

    printf ("%s\n", alphabet);


    strcpy(alphabet, newstring);

    return 0;
}

int main() {
   char* test="newstring";
   function1(test);

   printf ("%s\n", alphabet);

    return 0;

Answer 1

让我们看看 gcc 对您的代码有什么看法:

gcc -Wall test.c -o test

test.c: In function ‘function1’:
test.c:8:25: warning: comparison between pointer and integer
     while (newstring[i] != NULL) {
                         ^~
test.c:9:7: warning: implicit declaration of function ‘strcpy’ [-Wimplicit-function-declaration]
       strcpy(dest, newstring[i]);
       ^~~~~~
test.c:9:7: warning: incompatible implicit declaration of built-in function ‘strcpy’
test.c:9:7: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
test.c:9:20: warning: passing argument 2 of ‘strcpy’ makes pointer from integer without a cast [-Wint-conversion]
       strcpy(dest, newstring[i]);
                    ^~~~~~~~~
test.c:9:20: note: expected ‘const char *’ but argument is of type ‘char’
test.c: In function ‘main’:
test.c:19:20: warning: comparison between pointer and integer
     while (dest[i] != NULL) {
                    ^~
test.c:20:22: warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘int’ [-Wformat=]
       printf ("[%d] %s\n", i, dest[i]);
                      ^
test.c: At top level:
test.c:3:6: warning: array ‘dest’ assumed to have one element
 char dest[];
      ^~~~

正如您所看到的，有很多警告需要注意。

Take warnings seriously and fix them.

这样做的代码可能是:

#include <stdio.h>

char dest[32];

int function1(char* newstring) {
    // Or simply use strcpy instead of a loop... 
    int i = 0;
    while(newstring[i] != '\0')
    {
      dest[i] = newstring[i];
      ++i;
    }
    dest[i] = '\0';
    return 0;
}

int main() {
    char* test="newstring";
    function1(test);
    int i = 0;
    while (dest[i] != '\0') {
      printf ("[%d] %c\n", i, dest[i]);
      ++i;
    }
    return 0;
}

输出:

[0] n
[1] e
[2] w
[3] s
[4] t
[5] r
[6] i
[7] n
[8] g

注意 您还应该检查缓冲区溢出，即 i 始终小于 32。为了清楚起见，我省略了这一点，但请确保在代码之前添加它视为完成..