libc: picolibc: fputc should return the value it has written

[ycsin]

According to the documentations:

• en.cppreference.com/w/c/io/fputc

Return value

On success, returns the written character.
On failure, returns EOF and sets the error indicator (see ferror()) on stream.

• pubs.opengroup.org/onlinepubs/9699919799/functions/fputc.html

Upon successful completion, fputc() shall return the value it has written. Otherwise, it shall return EOF, the error indicator for the stream shall be set, [CX] [Option Start] and errno shall be set to indicate the error.

This commit changes it to return the written value on success, and EOF if failed, which is the same as minimal libc, but the error indicator is still not set.

zephyr/lib/libc/minimal/source/stdout/stdout_console.c

Lines 28 to 31 in 901a8f7

	int z_impl_zephyr_fputc(int c, FILE *stream)
	{
	return ((stream == stdout) || (stream == stderr)) ? _stdout_hook(c) : EOF;
	}

[keith-packard]

If I recall correctly, this is an internal implementation detail of the picolibc layer for Zephyr -- the actual fputc code seen by applications should come from picolibc itself and have the correct return value.

[ycsin]

If I recall correctly, this is an internal implementation detail of the picolibc layer for Zephyr -- the actual fputc code seen by applications should come from picolibc itself and have the correct return value.

I think you are right.

In that case, what's the role of zephyr_fputc() & picolibc_put() for picolibc? Just stubs?

[github-actions]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[keith-packard]

I think I already responded to this appropriately -- you are mis-understanding how these functions are used; they are implementation details specific to supporting the picolibc stdio stack on Zephyr. They are not the POSIX API used by applications.

[ycsin]

It was required for #74350, but @cfriedt already has something WIP in #84860, so I will close this.