1) Fix signature of _mpd_qpow_uint(): contrary to the comment base is constant.

2) Abort the loop for all specials, not only infinity.

3) Make the function more general and distinguish between zero clamping
   and folding down the exponent. The latter case is currently handled
   by setting context->clamp to 0 before calling the function.

1 files changed, 9 insertions, 7 deletions

diff --git a/Modules/_decimal/libmpdec/mpdecimal.c b/Modules/_decimal/libmpdec/mpdecimal.c
index ff6d867..262e834 100644
--- a/Modules/_decimal/libmpdec/mpdecimal.c
+++ b/Modules/_decimal/libmpdec/mpdecimal.c
@@ -107,8 +107,9 @@ static inline void _mpd_qmul(mpd_t *result, const mpd_t *a, const mpd_t *b,
                              const mpd_context_t *ctx, uint32_t *status);
 static void _mpd_base_ndivmod(mpd_t *q, mpd_t *r, const mpd_t *a,
                               const mpd_t *b, uint32_t *status);
-static inline void _mpd_qpow_uint(mpd_t *result, mpd_t *base, mpd_uint_t exp,
-                uint8_t resultsign, const mpd_context_t *ctx, uint32_t *status);
+static inline void _mpd_qpow_uint(mpd_t *result, const mpd_t *base,
+                                  mpd_uint_t exp, uint8_t resultsign,
+                                  const mpd_context_t *ctx, uint32_t *status);
 
 mpd_uint_t mpd_qsshiftr(mpd_t *result, const mpd_t *a, mpd_ssize_t n);
 
@@ -5841,12 +5842,12 @@ mpd_qnext_toward(mpd_t *result, const mpd_t *a, const mpd_t *b,
 }
 
 /*
- * Internal function: Integer power with mpd_uint_t exponent, base is modified!
- * Function can fail with MPD_Malloc_error.
+ * Internal function: Integer power with mpd_uint_t exponent. The function
+ * can fail with MPD_Malloc_error.
  */
 static inline void
-_mpd_qpow_uint(mpd_t *result, mpd_t *base, mpd_uint_t exp, uint8_t resultsign,
-               const mpd_context_t *ctx, uint32_t *status)
+_mpd_qpow_uint(mpd_t *result, const mpd_t *base, mpd_uint_t exp,
+               uint8_t resultsign, const mpd_context_t *ctx, uint32_t *status)
 {
     uint32_t workstatus = 0;
     mpd_uint_t n;
@@ -5866,7 +5867,8 @@ _mpd_qpow_uint(mpd_t *result, mpd_t *base, mpd_uint_t exp, uint8_t resultsign,
         if (exp & n) {
             mpd_qmul(result, result, base, ctx, &workstatus);
         }
-        if (workstatus & (MPD_Overflow|MPD_Clamped)) {
+        if (mpd_isspecial(result) ||
+            (mpd_iszerocoeff(result) && (workstatus & MPD_Clamped))) {
             break;
         }
     }