msvcrt: Implement %F format for strftime.

dlls/msvcrt/tests/time.c

@@ -614,6 +614,11 @@ static void test_strftime(void)
     ok(errno==EINVAL || broken(errno==0xdeadbeef), "errno = %d\n", errno);
 
     errno = 0xdeadbeef;
+    retA = p_strftime(bufA, 256, "%F", gmt_tm);
+    ok(retA == 0, "expected 0, got %ld\n", retA);
+    ok(errno==EINVAL || broken(errno==0xdeadbeef), "errno = %d\n", errno);
+
+    errno = 0xdeadbeef;
     retA = p_strftime(bufA, 256, "%R", gmt_tm);
     ok(retA == 0, "expected 0, got %ld\n", retA);
     ok(errno==EINVAL || broken(errno==0xdeadbeef), "errno = %d\n", errno);

dlls/msvcrt/time.c

@@ -1170,6 +1170,19 @@ static MSVCRT_size_t strftime_helper(char *str, MSVCRT_size_t max, const char *f
             if(!strftime_int(str, &ret, max, mstm->tm_year%100, alternate ? 0 : 2, 0, 99))
                 return 0;
             break;
+        case 'F':
+            tmp = 1900+mstm->tm_year;
+            if(!strftime_int(str, &ret, max, tmp, alternate ? 0 : 4, 0, 9999))
+                return 0;
+            if(ret < max)
+                str[ret++] = '-';
+            if(!strftime_int(str, &ret, max, mstm->tm_mon+1, alternate ? 0 : 2, 1, 12))
+                return 0;
+            if(ret < max)
+                str[ret++] = '-';
+            if(!strftime_int(str, &ret, max, mstm->tm_mday, alternate ? 0 : 2, 0, 31))
+                return 0;
+            break;
 #endif
         case 'H':
             if(!strftime_int(str, &ret, max, mstm->tm_hour, alternate ? 0 : 2, 0, 23))

dlls/ucrtbase/tests/misc.c

@@ -903,6 +903,14 @@ static void test_strftime(void)
     ok(retA == 6, "expected 6, got %d\n", (int)retA);
     ok(!strcmp(bufA, "1/1/70"), "got %s\n", bufA);
 
+    retA = p_strftime(bufA, sizeof(bufA), "%F", &epoch);
+    ok(retA == 10, "expected 10, got %d\n", (int)retA);
+    ok(!strcmp(bufA, "1970-01-01"), "got %s\n", bufA);
+
+    retA = p_strftime(bufA, sizeof(bufA), "%#F", &epoch);
+    ok(retA == 8, "expected 8, got %d\n", (int)retA);
+    ok(!strcmp(bufA, "1970-1-1"), "got %s\n", bufA);
+
     retA = p_strftime(bufA, sizeof(bufA), "%R", &epoch);
     ok(retA == 5, "expected 5, got %d\n", (int)retA);
     ok(!strcmp(bufA, "00:00"), "got %s\n", bufA);