libc: minimal: implement putc_unlocked & putchar_unlocked

Add a simple implementation for putc_unlocked() &
putchar_unlocked().

Signed-off-by: Yong Cong Sin <ycsin@meta.com>

doc/services/portability/posix/option_groups/index.rst

@@ -556,8 +556,8 @@ This table lists service support status in Zephyr for `POSIX_FD_MGMT`:
     funlockfile(), yes
     getc_unlocked(),
     getchar_unlocked(),
-    putc_unlocked(),
-    putchar_unlocked(),
+    putc_unlocked(), yes
+    putchar_unlocked(), yes
 
 .. _posix_option_group_multi_process:
 

lib/libc/minimal/include/stdio.h

@@ -62,6 +62,8 @@ size_t fwrite(const void *ZRESTRICT ptr, size_t size, size_t nitems,
 	      FILE *ZRESTRICT stream);
 #define putc(c, stream) fputc(c, stream)
 #define putchar(c) putc(c, stdout)
+#define putc_unlocked(c, stream) putc(c, stream)
+#define putchar_unlocked(c) putchar(c)
 
 void flockfile(FILE *file);
 int ftrylockfile(FILE *file);

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

@@ -59,12 +59,24 @@ int putc(int c, FILE *stream)
 	return zephyr_fputc(c, stream);
 }
 
+#undef putc_unlocked
+int putc_unlocked(int c, FILE *stream)
+{
+	return putc(c, stream);
+}
+
 #undef putchar
 int putchar(int c)
 {
 	return zephyr_fputc(c, stdout);
 }
 
+#undef putchar_unlocked
+int putchar_unlocked(int c)
+{
+	return putchar(c);
+}
+
 size_t z_impl_zephyr_fwrite(const void *ZRESTRICT ptr, size_t size,
 			    size_t nitems, FILE *ZRESTRICT stream)
 {

tests/lib/sprintf/src/main.c

@@ -890,6 +890,9 @@ ZTEST(sprintf, test_put)
 	ret = fputc('T', stderr);
 	zassert_equal(ret, 84, "fputc \'T\' failed");
 
+	ret = putc_unlocked('T', stdout);
+	zassert_equal(ret, 84, "putc \'T\' failed");
+
 	ret = fputc('T', stdin);
 	zassert_equal(ret, EOF, "fputc to stdin");
 }