Fix numeric_power() when the exponent is INT_MIN.

In power_var_int(), the computation of the number of significant
digits to use in the computation used log(Abs(exp)), which isn't safe
because Abs(exp) returns INT_MIN when exp is INT_MIN. Use fabs()
instead of Abs(), so that the exponent is cast to a double before the
absolute value is taken.

Back-patch to 9.6, where this was introduced (by 7d9a4737c2).

Discussion: https://postgr.es/m/CAEZATCVd6pMkz=BrZEgBKyqqJrt2xghr=fNc8+Z=5xC6cgWrWA@mail.gmail.com

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 73be69c740c1feb4a586be826aee885f13e6dd29..e347eaa885afb1233bbf6c3985e6b4fb73227681 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -8601,7 +8601,7 @@ power_var_int(const NumericVar *base, int exp, NumericVar *result, int rscale)
     * to around log10(abs(exp)) digits, so work with this many extra digits
     * of precision (plus a few more for good measure).
     */
-   sig_digits += (int) log(Abs(exp)) + 8;
+   sig_digits += (int) log(fabs(exp)) + 8;
 
    /*
     * Now we can proceed with the multiplications.

diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
index 1cb3c3bfab717cfe09fc953aedf6213b6c8b868d..7ea2c81afaca8b602df72a1bfd03c9bc407cdfdc 100644 (file)
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -1623,6 +1623,12 @@ select 0.12 ^ (-20);
  2608405330458882702.5529619561355838
 (1 row)
 
+select 1.000000000123 ^ (-2147483648);
+      ?column?      
+--------------------
+ 0.7678656556403084
+(1 row)
+
 -- cases that used to error out
 select 0.12 ^ (-25);
                  ?column?                  

diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
index a939412359625e2d910280f58bb24980f0995c35..4b8a7ca53ebe608e1ad6c9d58534dc56e7f56815 100644 (file)
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -896,6 +896,7 @@ select 3.789 ^ 21;
 select 3.789 ^ 35;
 select 1.2 ^ 345;
 select 0.12 ^ (-20);
+select 1.000000000123 ^ (-2147483648);
 
 -- cases that used to error out
 select 0.12 ^ (-25);