[libc][picolibc] improve gcc picolibc support

components/libc/compilers/picolibc/SConscript

@@ -1,10 +1,16 @@
 import os
 from building import *
-from llvm_arm import *
 Import('rtconfig')
 
 group = []
 
+if rtconfig.PLATFORM == 'gcc':
+  from gcc import *
+elif rtconfig.PLATFORM == 'llvm-arm':
+  from llvm_arm import *
+else:
+  Return('group')
+
 picolibc_version = GetPicoLibcVersion(rtconfig)
 
 if picolibc_version and not GetDepend('RT_USING_EXTERNAL_LIBC'):

components/libc/compilers/picolibc/exit.c

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2006-2023, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ */
+
+#include <rtthread.h>
+#include <sys/types.h>
+
+/* for exit() and abort() */
+rt_noreturn void _exit (int status)
+{
+    extern void __rt_libc_exit(int status);
+    __rt_libc_exit(status);
+    while(1);
+}

components/libc/compilers/picolibc/fcntl.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2006-2021, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2021-09-02     Meco Man     First version
+ */
+
+#ifndef __FCNTL_H__
+#define __FCNTL_H__
+
+#include <sys/_default_fcntl.h>
+
+#ifndef O_EXEC
+#define O_EXEC      0x400000
+#endif
+
+#ifndef O_TMPFILE
+#define O_TMPFILE   0x800000
+#endif
+
+#ifndef O_BINARY
+#define O_BINARY 0x10000
+#endif
+
+#ifndef O_NOFOLLOW
+#define O_NOFOLLOW 0x100000
+#endif
+
+#ifndef O_DIRECTORY
+#define O_DIRECTORY 0x200000
+#endif
+
+#endif

components/libc/compilers/picolibc/iob.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2006-2023, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ */
+
+#include <rtthread.h>
+#include <sys/types.h>
+#include <stdio.h>
+#include <unistd.h>
+#ifdef RT_USING_POSIX_STDIO
+#include <posix/stdio.h>
+#endif /* RT_USING_POSIX_STDIO */
+#define DBG_TAG    "picolibc.iob"
+#define DBG_LVL    DBG_INFO
+#include <rtdbg.h>
+
+#ifdef TINY_STDIO
+
+static int __fputc(char c, FILE *file);
+static int __fgetc(FILE *file);
+
+static FILE __stdio_in = FDEV_SETUP_STREAM(NULL, __fgetc, NULL, _FDEV_SETUP_READ);
+static FILE __stdio_out = FDEV_SETUP_STREAM(__fputc, NULL, NULL, _FDEV_SETUP_WRITE);
+
+#ifdef __strong_reference
+#define STDIO_ALIAS(x) __strong_reference(stdout, x);
+#else
+#define STDIO_ALIAS(x) FILE *const x = &__stdio_out;
+#endif
+
+FILE *const stdin = &__stdio_in;
+FILE *const stdout = &__stdio_out;
+STDIO_ALIAS(stderr);
+
+static int __fputc(char c, FILE *file)
+{
+    if (file == &__stdio_out)
+    {
+#if defined(RT_USING_CONSOLE) && defined(RT_USING_DEVICE)
+        rt_device_t console = rt_console_get_device();
+        if (console)
+        {
+            rt_ssize_t rc = rt_device_write(console, -1, &c, 1);
+            return rc > 0 ? rc : -1;
+        }
+#endif /* defined(RT_USING_CONSOLE) && defined(RT_USING_DEVICE) */
+    }
+
+    return -1;
+}
+
+static int __fgetc(FILE *file)
+{
+    if (file == &__stdio_in)
+    {
+#ifdef RT_USING_POSIX_STDIO
+        if (rt_posix_stdio_get_console() >= 0)
+        {
+            char c;
+            int rc = read(STDIN_FILENO, &c, 1);
+            return rc == 1 ? c : EOF;
+        }
+#endif /* RT_USING_POSIX_STDIO */
+    }
+
+    return EOF;
+}
+
+#endif