ffi: bugfix: char array shouldn't null terminate.

* ffi.c (ffi_char_array_put): The char array put operation
should only null terminate when the null_term flag is set;
i.e. it's a zarray type. The bug here is that when a Lisp
string of length > N is put into an (array N char), the
C array gets null terminated, which is wrong. Only in the case
when the string is exactly of length N is there no null
termination.  In all cases when the length >= N, we want
truncation without null termination.

1 files changed, 3 insertions, 1 deletions

diff --git a/ffi.c b/ffi.c
index fc21c7de..b11f0d42 100644
--- a/ffi.c
+++ b/ffi.c
@@ -2258,9 +2258,11 @@ static void ffi_char_array_put(struct txr_ffi_type *tft, val str, mem_t *dst,
   } else {
     char *u8str = utf8_dup_to(wstr);
     memcpy(dst, u8str, nelem);
-    dst[nelem - 1] = 0;
     free(u8str);
   }
+
+  if (nt)
+    dst[nelem - 1] = 0;
 }
 
 static val ffi_wchar_array_get(struct txr_ffi_type *tft, mem_t *src,