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 74335f76f5c52cbddc3b63640bde47f6fdf6d3fc..f50da658a634fe7c7b3585e107cf1328a6c8f592 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -8182,7 +8182,7 @@ power_var_int(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 35a0f9cd42ddc4813f9e53b8df25758e286e3998..ae1daa5744e99cf27e48c552b25232deb04df21f 100644 (file)
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -1506,6 +1506,12 @@ 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 c2d73c2d0b9ae054ad4179ca2bd15569f8b723b2..d6ff9b8a399d67c9bd8e0ce939992405cfd3835d 100644 (file)
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -873,6 +873,7 @@ 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);