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    <p>A memory leak occurs when you request memory with <code>malloc()</code> and don't <code>free()</code> the memory. </p> <h1>Bad example</h1> <pre><code>#include &lt;stdlib.h&gt; int main(int argc, char *argv[]) { int *nums = malloc(10 * sizeof(int)); // create array with memory for 10 nums nums[0] = 2; nums[4] = 8; return 0; // main() ended but nums wasn't free'd. Memory leak/ } </code></pre> <h1>Good example</h1> <pre><code>#include &lt;stdlib.h&gt; int main(int argc, char *argv[]) { int *nums = malloc(10 * sizeof(int)); // create array with memory for 10 nums nums[0] = 2; nums[4] = 8; free(nums); // free memory allocated for nums return 0; } </code></pre> <p>Now about your programs.</p> <h1>1 - reformatted</h1> <p>This program will never end and forever call x (and thus print Hello World! till the end of times)</p> <pre><code>#include &lt;stdio.h&gt; void x(void) { printf("Hello World!\n"); } int main(int argc, char *argv[]) { while (1) x(); return 0; } </code></pre> <h1>2 - reformatted</h1> <p>This program allocates memory for 100 integers every loop but never free's this memory. Huge memory leak that keeps going until the OS is out of memory.</p> <pre><code>#include &lt;stdlib.h&gt; int main(int argc, char *argv[]) { int *x; while (1) { x = malloc(100 * size(int)); // allocate memory for an array of 100 integers } return 0; } </code></pre> <h1>3 - reformatted</h1> <p>This program keeps recursing until the stack is exhausted (stack trace) and the program will crash (stack overflow).</p> <pre><code>void x(void) { x(); } int main(int argc, char *argv[]) { x(); return 0; } </code></pre>
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    1. COActually your bad example isn't that bad. When the program ends those bytes will be freed regardless of whether or not the program explicitly frees them. Memory leaks are only an issue while the program continues to run. When it terminates, the OS reclaims all the memory that was allocated to it.
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    2. CO@aroth: Depends on the OS and is not guaranteed by the C standard.
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    3. COIt shouldn't matter what the C standard says (and the C standard shouldn't be making guarantees about anything the OS does when a program terminates anyways). The OS deals in executable code, and has no way of knowing that program X was written in C. If the OS leaves anything resident in memory after a program terminates then that is a bug in the OS, and has nothing to do with anything the program did or did not do.
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