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POPrevent leak after Ctrl+C when using read and malloc in a loop
 

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    <p>I have to do a project, creating a shell in C. There will be a while loop waiting for characters to read in input.</p> <p>I think it's better to store characters we read in a pointer using <code>malloc</code> than in a buffer (array of characters) with fixed sized because we don't know how many characters will be sent. This way, I could use <code>realloc</code> on the pointer to get a larger size if needed.</p> <p>I've noticed with valgrind that when the program has finished reading characters and is waiting for new ones; if I press Ctrl+C, there will be memory leak. The only solution I've found to prevent this is to free the pointer after each command sent.</p> <p>Is this a good idea or is there a better way to do this? For information, I'm reading characters in a buffer buf and then concatenating string to the pointer str. Here is the code:</p> <pre><code>#include &lt;unistd.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;stdio.h&gt; #define READ_SIZE 1024 int main() { char buf[READ_SIZE]; char *str; int ret; int size; int max; str = NULL; size = 0; max = READ_SIZE; write(1, "$&gt; ", 3); while((ret = read(0, buf, READ_SIZE))) { if (str == NULL) { if ((str = malloc(READ_SIZE + 1)) == NULL) return EXIT_FAILURE; strncpy(str, buf, ret); str[ret] = '\0'; } else str = strncat(str, buf, ret); if (strncmp(&amp;buf[ret - 1], "\n", 1) == 0) { str[size + ret - 1] = '\0'; printf("%s\n", str); size = 0; max = READ_SIZE; free(str); str = NULL; write(1, "$&gt; ", 3); } else if (size + ret == max) { max *= 2; size += READ_SIZE; if ((str = realloc(str, max + 1)) == NULL) return EXIT_FAILURE; } else size += READ_SIZE; } free(str); return EXIT_SUCCESS; } </code></pre>
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