[PATCH 1/2] tools/nolibc: add stdarg.h header

[Thomas Weißschuh]

This allows nolic to work with `-nostdinc` avoiding any reliance on
system headers.

The implementation has been lifted from musl libc 1.2.4.
There is already an implementation of stdarg.h in include/linux/stdarg.h
but that is GPL licensed and therefore not suitable for nolibc.

The used compiler builtins have been validated to be at least available
since GCC 4.1.2 and clang 3.0.0.

Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
 tools/include/nolibc/Makefile |  1 +
 tools/include/nolibc/stdarg.h | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
index 909b6eb500fe..e69c26abe1ea 100644
--- a/tools/include/nolibc/Makefile
+++ b/tools/include/nolibc/Makefile
@@ -34,6 +34,7 @@ all_files := \
 		signal.h \
 		stackprotector.h \
 		std.h \
+		stdarg.h \
 		stdint.h \
 		stdlib.h \
 		string.h \
diff --git a/tools/include/nolibc/stdarg.h b/tools/include/nolibc/stdarg.h
new file mode 100644
index 000000000000..c628b5783da6
--- /dev/null
+++ b/tools/include/nolibc/stdarg.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Variadic argument support for NOLIBC
+ * Copyright (C) 2005-2020 Rich Felker, et al.
+ */
+
+#ifndef _NOLIBC_STDARG_H
+#define _NOLIBC_STDARG_H
+
+typedef __builtin_va_list va_list;
+#define va_start(v, l)   __builtin_va_start(v, l)
+#define va_end(v)        __builtin_va_end(v)
+#define va_arg(v, l)     __builtin_va_arg(v, l)
+#define va_copy(d, s)    __builtin_va_copy(d, s)
+
+#endif /* _NOLIBC_STDARG_H */

-- 
2.42.0