'

beware_overflow/beware_overflow.c

@@ -0,0 +1,11 @@
+#include "beware_overflow.h"
+
+void *beware_overflow(void *ptr, size_t nmemb, size_t size)
+{
+    size_t c;
+    if (__builtin_mul_overflow(nmemb, size, &c))
+        return NULL;
+
+    char *byte_ptr = ptr;
+    return c + byte_ptr;
+}

beware_overflow/beware_overflow.h

@@ -0,0 +1,8 @@
+#ifndef BEWARE_OVERFLOW_H
+#define BEWARE_OVERFLOW_H
+
+#include <stddef.h>
+
+void *beware_overflow(void *ptr, size_t nmemb, size_t size);
+
+#endif /* BEWARE_OVERFLOW_H */

beware_overflow/main.c

@@ -0,0 +1,21 @@
+#include <stddef.h>
+#include <stdio.h>
+
+#include "beware_overflow.h"
+
+void print_overflow(void *ptr, size_t nmemb, size_t size)
+{
+    void *begin = ptr;
+    void *res = beware_overflow(ptr, nmemb, size);
+    if (res)
+        printf("Pointer was incremented from %p to %p.\n", begin, res);
+    else
+        printf("Overflow detected between %ld and %ld.\n", nmemb, size);
+}
+
+int main(void)
+{
+    print_overflow((void *)0x1000, 25, 6);
+    print_overflow((void *)0x40000, 12345678904, 12345678904);
+    return 0;
+}