lib/string/sprintf/, lib/, src/, tests/: Move all sprintf(3)-like APIs to a subdirectory

And have a separate file for each pair of APIs.

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

lib/string/sprintf/xasprintf.h

@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: 2023-2024, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_STRING_SPRINTF_XASPRINTF_H_
+#define SHADOW_INCLUDE_LIB_STRING_SPRINTF_XASPRINTF_H_
+
+
+#include <config.h>
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "attr.h"
+
+
+format_attr(printf, 2, 3)
+inline int xasprintf(char **restrict s, const char *restrict fmt, ...);
+format_attr(printf, 2, 0)
+inline int xvasprintf(char **restrict s, const char *restrict fmt, va_list ap);
+
+
+inline int
+xasprintf(char **restrict s, const char *restrict fmt, ...)
+{
+	int      len;
+	va_list  ap;
+
+	va_start(ap, fmt);
+	len = xvasprintf(s, fmt, ap);
+	va_end(ap);
+
+	return len;
+}
+
+
+inline int
+xvasprintf(char **restrict s, const char *restrict fmt, va_list ap)
+{
+	int  len;
+
+	len = vasprintf(s, fmt, ap);
+	if (len == -1) {
+		perror("asprintf");
+		exit(EXIT_FAILURE);
+	}
+
+	return len;
+}
+
+
+#endif  // include guard