casaroli opened a new pull request, #20633:
URL: https://github.com/apache/nuttx/pull/20633
## Summary
A line buffered stream is flushed at a newline only by `fputc()`, `fputs()`
and `puts()`. `printf()` writes through `fwrite()`, so a line that `printf()`
writes to a line buffered stream (stdout or stderr on a terminal) stays in the
buffer until the buffer is full or the program exits. The output of stderr
comes after later lines of stdout, and complete lines are lost when the program
ends with `_exit()` or `abort()`.
This PR flushes the stream in `lib_fwrite_unlocked()` when the stream is
line buffered and the data holds a newline.
The first commit fixes an old nxstyle error in `lib_libfwrite.c` (a missing
blank line), so that checkpatch passes on the file.
## Impact
`fwrite()`, `printf()`, `fprintf()` and `vfprintf()` on line buffered
streams (`CONFIG_STDIO_BUFFER_SIZE` > 0): a line is now written when the
newline is written, as C and POSIX require. Fully buffered streams do not
change.
## Testing
`qemu-armv8a:knsh`, with these commits on a larger local branch. A test
program writes four lines, alternating `fprintf(stderr, ...)` and `printf()`,
with an `fflush(stdout)` after the second line:
```
fprintf(stderr, "stdbuf: 1 stderr\n");
printf("stdbuf: 2 stdout\n");
fflush(stdout);
fprintf(stderr, "stdbuf: 3 stderr\n");
printf("stdbuf: 4 stdout\n");
```
Before: "stdbuf: 1 stderr" came out after "stdbuf: 2 stdout", because stderr
was flushed only at exit.
After: the four lines come out in program order.
Build: `qemu-armv8a:nsh`, `qemu-armv8a:knsh` and `lm3s6965-ek:qemu-flat`.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
