1 files changed, 27 insertions, 5 deletions

diff --git a/src/lj_strfmt.c b/src/lj_strfmt.c
index 5826b539..7b073470 100644
--- a/src/lj_strfmt.c
+++ b/src/lj_strfmt.c
@@ -16,6 +16,9 @@
 #include "lj_state.h"
 #include "lj_char.h"
 #include "lj_strfmt.h"
+#if LJ_HASFFI
+#include "lj_ctype.h"
+#endif
 #include "lj_lib.h"
 
 /* -- Format parser ------------------------------------------------------- */
@@ -392,15 +395,34 @@ int lj_strfmt_putarg(lua_State *L, SBuf *sb, int arg, int retry)
             lj_strfmt_putint(sb, k);  /* Shortcut for plain %d. */
           else
             lj_strfmt_putfxint(sb, sf, k);
-        } else {
-          lj_strfmt_putfnum_int(sb, sf, lj_lib_checknum(L, arg));
+          break;
+        }
+#if LJ_HASFFI
+        if (tviscdata(o)) {
+          GCcdata *cd = cdataV(o);
+          if (cd->ctypeid == CTID_INT64 || cd->ctypeid == CTID_UINT64) {
+            lj_strfmt_putfxint(sb, sf, *(uint64_t *)cdataptr(cd));
+            break;
+          }
         }
+#endif
+        lj_strfmt_putfnum_int(sb, sf, lj_lib_checknum(L, arg));
         break;
       case STRFMT_UINT:
-        if (tvisint(o))
+        if (tvisint(o)) {
           lj_strfmt_putfxint(sb, sf, intV(o));
-        else
-          lj_strfmt_putfnum_uint(sb, sf, lj_lib_checknum(L, arg));
+          break;
+        }
+#if LJ_HASFFI
+        if (tviscdata(o)) {
+          GCcdata *cd = cdataV(o);
+          if (cd->ctypeid == CTID_INT64 || cd->ctypeid == CTID_UINT64) {
+            lj_strfmt_putfxint(sb, sf, *(uint64_t *)cdataptr(cd));
+            break;
+          }
+        }
+#endif
+        lj_strfmt_putfnum_uint(sb, sf, lj_lib_checknum(L, arg));
         break;
       case STRFMT_NUM:
         lj_strfmt_putfnum(sb, sf, lj_lib_checknum(L, arg));