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

@@ -569,8 +569,8 @@ 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_memory_protection:
 

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/posix/options/file_locking.c

@@ -35,3 +35,15 @@ void funlockfile(FILE *file)
 #ifdef CONFIG_POSIX_FD_MGMT_ALIAS_FUNLOCKFILE
 FUNC_ALIAS(funlockfile, _funlockfile, void);
 #endif /* CONFIG_POSIX_FD_MGMT_ALIAS_FUNLOCKFILE */
+
+#undef putc_unlocked
+int putc_unlocked(int c, FILE *stream)
+{
+	return putc(c, stream);
+}
+
+#undef putchar_unlocked
+int putchar_unlocked(int c)
+{
+	return putchar(c);
+}

tests/posix/common/src/file_locking.c

@@ -11,6 +11,8 @@
 void flockfile(FILE *file);
 int ftrylockfile(FILE *file);
 void funlockfile(FILE *file);
+int putc_unlocked(int, FILE *);
+int putchar_unlocked(int);
 #endif
 
 #include <zephyr/sys/fdtable.h>
@@ -114,4 +116,11 @@ ZTEST(file_locking, test_file_locking)
 	zassert_not_ok(ftrylockfile(file));
 }
 
+ZTEST(file_locking, test_stdio)
+{
+	int ret;
+
+	ret = putc_unlocked('T', stdout);
+	zassert_equal(ret, 84, "putc \'T\' failed");
+}
 ZTEST_SUITE(file_locking, NULL, NULL, NULL, NULL, NULL);