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 553e261ed00938cb53af1665e4eb90ed638b90b4..7582aa304329a1c459388b38f86a759a2729157d 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -9370,7 +9370,7 @@ 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 c7fe63d03744432094f86e28532dd928f0ed43e8..c05bf7b8e6a6f680fe5bc7a7861793033c9ff3cc 100644 (file)
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -1674,6 +1674,12 @@ 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 41475a9a245f44d063e57c3a5ad62eb49f2848a0..6fa8d3fcc0b06e1b64e0e218c30dd43aa053d407 100644 (file)
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -909,6 +909,7 @@ 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);