> Or we could simply require the user to use C99/C++11 for generated
> reproducers.  That's probably simplest.

I think that is fine. It's a debugging and test tool anyway.

I added the following include guards for long long (in the first patch of the series):

+#ifdef __GNUC__
+
+/* Include entrypoints with long long parameter types. */
+#  define LIBGCCJIT_INCLUDE_LONGLONGS
+
+#else
+
+#  if __STDC_VERSION__ >= 199901L
+#    define LIBGCCJIT_INCLUDE_LONGLONGS
+#  elif __cplusplus >= 201103L
+#    define LIBGCCJIT_INCLUDE_LONGLONGS
+#  endif
+
+#endif
+

> "arr" should probably be const, and "len" be a size_t.

+reproducer_write_arr (reproducer &r, const unsigned char *arr, size_t len)

> FWIW "LIBGCCJIT_HAVE_LONGLONG_CONSTANTS" doesn't seem quite like the
> right name here, but I wasn't able to come up with a better one.

I changed it to LIBGCCJIT_HAVE_LOONG_CONSTANTS. I think it better conveys
it is long long, _Complex long double and long double.

> Is this a typo for "typepunning"...

+/* For typepunning NaNs. */


make check-jit runs fine.