Update MentOs code to the latest development version.

libc/src/stdlib.c

@@ -0,0 +1,91 @@
+///                MentOS, The Mentoring Operating system project
+/// @file stdlib.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include "system/syscall_types.h"
+#include "stdlib.h"
+#include "string.h"
+#include "assert.h"
+
+/// @brief Number which identifies a memory area allocated through a call to
+/// malloc(), calloc() or realloc().
+#define MALLOC_MAGIC_NUMBER 0x600DC0DE
+
+static inline int __malloc_is_valid_ptr(void *ptr)
+{
+    return (ptr && (((size_t *)ptr)[-1] == MALLOC_MAGIC_NUMBER));
+}
+
+size_t malloc_usable_size(void *ptr)
+{
+    if (__malloc_is_valid_ptr(ptr))
+        return ((size_t *)ptr)[-2];
+    return 0;
+}
+
+void *malloc(unsigned int size)
+{
+    size_t *_res, _size = 2 * sizeof(size_t) + size;
+    __inline_syscall1(_res, brk, _size);
+    _res[0] = size;
+    _res[1] = MALLOC_MAGIC_NUMBER;
+    return &_res[2];
+}
+
+void *calloc(size_t num, size_t size)
+{
+    void *ptr = malloc(num * size);
+    if (ptr) {
+        memset(ptr, 0, num * size);
+    }
+    return ptr;
+}
+
+void *realloc(void *ptr, size_t size)
+{
+    // C standard implementation: When NULL is passed to realloc,
+    // simply malloc the requested size and return a pointer to that.
+    if (__builtin_expect(ptr == NULL, 0)) {
+        return malloc(size);
+    }
+    // C standard implementation: For a size of zero, free the
+    // pointer and return NULL, allocating no new memory.
+    if (__builtin_expect(size == 0, 0)) {
+        free(ptr);
+        return NULL;
+    }
+    // Get the old size.
+    size_t old_size = malloc_usable_size(ptr);
+    // Create the new pointer.
+    void *newp = malloc(size);
+    memset(newp, 0, size);
+    memcpy(newp, ptr, old_size);
+    free(ptr);
+    return newp;
+}
+
+void free(void *ptr)
+{
+    int _res;
+    if (__malloc_is_valid_ptr(ptr)) {
+        size_t *_ptr = (size_t *)ptr - 2;
+        __inline_syscall1(_res, brk, _ptr);
+    } else {
+        __inline_syscall1(_res, brk, ptr);
+    }
+}
+
+/// Seed used to generate random numbers.
+static int rseed = 0;
+
+void srand(int x)
+{
+    rseed = x;
+}
+
+int rand()
+{
+    return rseed = (rseed * 1103515245U + 12345U) & RAND_MAX;
+}