tools/nolibc/stdio: add a minimal set of stdio functions

This only provides getchar(), putchar(), and puts().

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/nolibc.h

@@ -88,6 +88,7 @@
 #include "types.h"
 #include "sys.h"
 #include "ctype.h"
+#include "stdio.h"
 #include "stdlib.h"
 #include "string.h"
 

tools/include/nolibc/stdio.h

@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * minimal stdio function definitions for NOLIBC
+ * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
+ */
+
+#ifndef _NOLIBC_STDIO_H
+#define _NOLIBC_STDIO_H
+
+#include "std.h"
+#include "arch.h"
+#include "types.h"
+#include "sys.h"
+#include "stdlib.h"
+#include "string.h"
+
+#ifndef EOF
+#define EOF (-1)
+#endif
+
+static __attribute__((unused))
+int getchar(void)
+{
+	unsigned char ch;
+
+	if (read(0, &ch, 1) <= 0)
+		return EOF;
+	return ch;
+}
+
+static __attribute__((unused))
+int putchar(int c)
+{
+	unsigned char ch = c;
+
+	if (write(1, &ch, 1) <= 0)
+		return EOF;
+	return ch;
+}
+
+static __attribute__((unused))
+int puts(const char *s)
+{
+	size_t len = strlen(s);
+	ssize_t ret;
+
+	while (len > 0) {
+		ret = write(1, s, len);
+		if (ret <= 0)
+			return EOF;
+		s += ret;
+		len -= ret;
+	}
+	return putchar('\n');
+}
+
+#endif /* _NOLIBC_STDIO_H */