lib/strdup/: STRDUPA(): Add macro

This is like strdupa(3), but we make sure that the argument is a string
literal, which makes sure that we won't have a stack overflow.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/Makefile.am

@@ -202,6 +202,8 @@ libshadow_la_SOURCES = \
 	string/strcpy/strncpy.h \
 	string/strcpy/strtcpy.c \
 	string/strcpy/strtcpy.h \
+	string/strdup/strdupa.c \
+	string/strdup/strdupa.h \
 	string/strdup/strndupa.c \
 	string/strdup/strndupa.h \
 	string/strdup/xstrdup.c \

lib/string/strdup/strdupa.c

@@ -0,0 +1,7 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#include <config.h>
+
+#include "string/strdup/strdupa.h"

lib/string/strdup/strdupa.h

@@ -0,0 +1,18 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_STRING_STRDUP_STRDUPA_H_
+#define SHADOW_INCLUDE_LIB_STRING_STRDUP_STRDUPA_H_
+
+
+#include <config.h>
+
+#include <string.h>
+
+
+// strdupa(3), but make sure that the argument is a string literal.
+#define STRDUPA(s)  strdupa("" s "")
+
+
+#endif  // include guard