Support va_args in libc-builtin (#1117)

Implement vprintf/sprintf/snprintf wrapper functions for libc-builtin.

core/iwasm/libraries/libc-builtin/libc_builtin_wrapper.c

@@ -1067,6 +1067,9 @@ static NativeSymbol native_symbols_libc_builtin[] = {
     REG_NATIVE_FUNC(printf, "($*)i"),
     REG_NATIVE_FUNC(sprintf, "($$*)i"),
     REG_NATIVE_FUNC(snprintf, "(*~$*)i"),
+    { "vprintf", printf_wrapper, "($*)i", NULL },
+    { "vsprintf", sprintf_wrapper, "($$*)i", NULL },
+    { "vsnprintf", snprintf_wrapper, "(*~$*)i", NULL },
     REG_NATIVE_FUNC(puts, "($)i"),
     REG_NATIVE_FUNC(putchar, "(i)i"),
     REG_NATIVE_FUNC(memcmp, "(**~)i"),

wamr-sdk/app/libc-builtin-sysroot/include/stdarg.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#ifndef _WAMR_LIBC_STDARG_H
+#define _WAMR_LIBC_STDARG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef _VA_LIST
+typedef __builtin_va_list va_list;
+#define _VA_LIST
+#endif
+#define va_start(ap, param) __builtin_va_start(ap, param)
+#define va_end(ap) __builtin_va_end(ap)
+#define va_arg(ap, type) __builtin_va_arg(ap, type)
+
+#define __va_copy(d, s) __builtin_va_copy(d, s)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* end of _WAMR_LIBC_STDARG_H */

wamr-sdk/app/libc-builtin-sysroot/share/defined-symbols.txt

@@ -26,6 +26,9 @@ wasm_get_sys_tick_ms
 printf
 sprintf
 snprintf
+vprintf
+vsprintf
+vsnprintf
 puts
 putchar
 memcmp