user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/ansi/freopen.c

@@ -0,0 +1,49 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#ifdef USE_HOST_LIBC
+#define TEST_FILE "freopen-host-libc.tmp"
+#else
+#define TEST_FILE "freopen.tmp"
+#endif
+
+int main() {
+	FILE *file = fopen(TEST_FILE, "w");
+	assert(file);
+
+	assert(freopen("/dev/null", "w", file));
+
+	char str[] = "mlibc freopen test";
+	fwrite(str, 1, sizeof(str) - 1, file);
+	fflush(file);
+	fclose(file);
+
+	file = fopen(TEST_FILE, "r");
+	assert(file);
+
+	char buf[sizeof(str)];
+	memset(buf, 0, sizeof(buf));
+	int ret = fread(buf, 1, sizeof(buf) - 1, file);
+	fprintf(stderr, "ret %d\n", ret);
+	assert(ret == 0);
+	fclose(file);
+
+	file = fopen("/dev/null", "w");
+	assert(file);
+
+	assert(freopen(TEST_FILE, "w", file));
+	fwrite(str, 1, sizeof(str) - 1, file);
+	fflush(file);
+	fclose(file);
+
+	memset(buf, 0, sizeof(buf));
+	file = fopen(TEST_FILE, "r");
+	assert(fread(buf, 1, sizeof(buf) - 1, file));
+
+	fprintf(stderr, "buffer content '%s'\n", buf);
+	assert(!strcmp(buf, "mlibc freopen test"));
+	fclose(file);
+
+	return 0;
+}