'read' function should return 0 when encountering an end of file. When
newlib calls read and sees EOF returned, it assumes that this
condition is permanent and never calls 'read' for this file again
(unless the read pointer is moved using fseek).
The correct behavior in case no characters were received over UART is
to return -1. In this case newlib will retry reading from file on next
call to fread, fgetc or another function which calls __srefill_r.
Since these functions receive the pointer to reent structure, they
should set errno in it rather than using thread-local errno.
This didn't cause practical issues because console functions in IDF
are only called from threads, and in that case 'r' is a pointer to
the thread-local structure, so &errno is the same thing as
&__errno_r(r). Still, fixing this for consistency.
When CONFIG_VFS_SUPPORT_IO is disabled, _read_r and _write_r
implementations in syscalls.c are used to provide console I/O via
esp_rom_uart_tx_one_char/esp_rom_uart_rx_one_char.
When newlib opens a (FILE*) stream, it calls fstat to check if the
underlying file is character-oriented. In this case, it configures the
stream to use line buffering. Otherwise (or if fstat fails) the stream
is opened as block buffered.
Since fstat wasn't provided, stdin/stdout/stderr streams got opened in
block buffered mode. For console, we need line buffered output so that
the stream buffer is flushed each time a complete line (ending with
'\n') is sent to stdout or stderr.
Fix by implementing _fstat_r stub, setting st->st_mdoe=S_IFCHR.
* Target components pull in xtensa component directly
* Use CPU HAL where applicable
* Remove unnecessary xtensa headers
* Compilation changes necessary to support non-xtensa gcc types (ie int32_t/uint32_t is no
longer signed/unsigned int).
Changes come from internal branch commit a6723fc
- spaces->tabs in tasks.c
- update vfs_uart.c to use per-UART locks
- add license to vfs_uart.c
- allocate separate streams for stdout, stdin, stderr, so that they can be independently reassigned
- fix build system test failure
