memzero.[ch]: Define memzero() and strzero() as inline functions

There's no need to have these as macros, so use functions, which are a
lot safer: there's no need to worry about multiple evaluation of args,
and there's also more type safety.  Compiler warnings are also simpler,
as they don't dump all the nested macros.

Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/Makefile.am

@@ -85,6 +85,7 @@ libshadow_la_SOURCES = \
 	mail.c \
 	mempcpy.c \
 	mempcpy.h \
+	memzero.c \
 	memzero.h \
 	motd.c \
 	myname.c \

lib/memzero.c

@@ -0,0 +1,17 @@
+/*
+ * SPDX-FileCopyrightText: 2023, Alejandro Colomar <alx@kernel.org>
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+#include <config.h>
+
+#ident "$Id$"
+
+#include <stddef.h>
+
+#include "memzero.h"
+
+
+extern inline void memzero(void *ptr, size_t size);
+extern inline void strzero(char *s);

lib/memzero.h

@@ -1,5 +1,6 @@
 /*
  * SPDX-FileCopyrightText: 2022-2023, Christian Göttsche <cgzones@googlemail.com>
+ * SPDX-FileCopyrightText: 2023, Alejandro Colomar <alx@kernel.org>
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
@@ -15,19 +16,29 @@
 #include <strings.h>
 
 
-#ifdef HAVE_MEMSET_EXPLICIT
-# define memzero(ptr, size) memset_explicit((ptr), 0, (size))
-#elif defined HAVE_EXPLICIT_BZERO
-# define memzero(ptr, size) explicit_bzero((ptr), (size))
-#else
-static inline void memzero(void *ptr, size_t size)
+inline void memzero(void *ptr, size_t size);
+inline void strzero(char *s);
+
+
+inline void
+memzero(void *ptr, size_t size)
 {
+#if defined(HAVE_MEMSET_EXPLICIT)
+	memset_explicit(ptr, 0, size);
+#elif defined(HAVE_EXPLICIT_BZERO)
+	explicit_bzero(ptr, size);
+#else
 	ptr = memset(ptr, '\0', size);
 	__asm__ __volatile__ ("" : : "r"(ptr) : "memory");
-}
 #endif
+}
 
-#define strzero(s) memzero(s, strlen(s))	/* warning: evaluates twice */
+
+inline void
+strzero(char *s)
+{
+	memzero(s, strlen(s));
+}
 
 
 #endif  // include guard