libc: io: vprintf now checks for stream error before returning

lib/libc/io/stdio/vprintf.c

@@ -1,19 +1,20 @@
 #include "file.h"
 
 #include <stddef.h>
+#include <errno.h>
 #include <stdio.h>
 
 extern int __libc_fctprintf(
-	void (*out)(char character, void *arg),
+	int (*out)(char character, void *arg),
 	void *arg,
 	const char *format,
 	va_list va);
 extern int __fputc(int c, struct __opaque_file *stream);
 
-static inline void _out_file(char character, void *arg)
+static inline int  _out_file(char character, void *arg)
 {
-	struct __opaque_file *fp = arg;
+	FILE *fp = arg;
-	__fputc(character, fp);
+	return __fputc(character, fp);
 }
 
 int vprintf(const char *format, va_list arg)
@@ -21,6 +22,13 @@ int vprintf(const char *format, va_list arg)
 	__libc_file_lock(stdout);
 
 	int ret = __libc_fctprintf(_out_file, stdout, format, arg);
+	if (errno != SUCCESS) {
+		ret = -1;
+	}
+
+	if (ferror(stdout)) {
+		ret = -1;
+	}
 
 	__libc_file_unlock(stdout);
 	return ret;