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 1463ae66b71d10e87a141c5e53021419fa7b4664..0bb2a7a9a3de49a169d9a03b8c45f65a4d0e4b89 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -8265,7 +8265,7 @@ 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 7e55b0e2931bf3228064753947d4ad7660d42df5..b4c78a2b722b384ad712a5e44d1b96624c274071 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 9675b6eabf3110da2683824c9a2bfd24914b88d0..7b3e818e928953a16d7764ac2f69b1694038f178 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);