C: add mem/safe_mem.*

c-programming/mem/safe_mem.h

@@ -0,0 +1,65 @@
+/*
+ * safe_mem.h
+ *
+ * A header-only library (macro collection) for safer memory management.
+ *
+ * Author: Intel A80486DX2-66
+ * License: Creative Commons Zero 1.0 Universal
+ */
+
+#ifndef _SAFE_MEM_H
+#define _SAFE_MEM_H
+
+#include <stdlib.h>
+
+#define SAFE_FREE_ERROR_HOOK /* user-defined */
+
+#define safe_free(ptr) do {                                                   \
+    /* prevents NULL-freeing and double freeing */                            \
+    if (ptr != NULL) {                                                        \
+        free(ptr);                                                            \
+        ptr = NULL;                                                           \
+    } else { SAFE_FREE_ERROR_HOOK; }                                          \
+} while (0)
+
+#define precise_malloc(nmemb, size)                                           \
+    /* prevents incorrect casting */                                          \
+    malloc((size_t) nmemb * (size_t) size)
+
+/* secure_erase(dest, count): erases memory explicitly */
+#if defined(__FreeBSD__)
+# define NO_SECURE_ERASE_WARRANTY 0
+# define SECURE_ERASE_WARRANTY "OpenBSD/FreeBSD: explicit_bzero"
+
+# include <strings.h>
+# define secure_erase explicit_bzero
+#elif defined(_WIN32)
+# define NO_SECURE_ERASE_WARRANTY 0
+# define SECURE_ERASE_WARRANTY "Microsoft Windows: SecureZeroMemory"
+
+# include <windows.h>
+# define secure_erase SecureZeroMemory
+#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
+# define NO_SECURE_ERASE_WARRANTY 0
+# define SECURE_ERASE_WARRANTY "C11+: memset_s"
+
+# define secure_erase(dest, count) memset_s(dest, count, 0, count)
+#else
+# define NO_SECURE_ERASE_WARRANTY 1
+
+# define __observe__(ptr) do {                                                \
+    if (*ptr == 0) {                                                          \
+        ++(*ptr);                                                             \
+        fprintf(stderr, "");                                                  \
+    } else                                                                    \
+        --(*ptr);                                                             \
+} while (0)
+
+# define secure_erase(dest, count) do {                                       \
+    memset(dest, 0, count);                                                   \
+    for (size_t i = 0; i < count; i++)                                        \
+        __observe__(dest[i]);                                                 \
+} while (0)
+#endif
+
+#endif /* _SAFE_MEM_H */