doc: Document error handling in PGTYPESnumeric_to_long

The documentation for PGTYPESnumeric_to_long only mentioned errno
being set to indicate overflow but the code also sets errno when
underflow happens.

Reported-by: Aidar Imamov 
Discussion: https://postgr.es/m/eebf0ad50ad4321d65d2d64dd6b7f17d@postgrespro.ru

diff --git a/doc/src/sgml/ecpg.sgml b/doc/src/sgml/ecpg.sgml
index ab58729e6ec295c73ea507c6033e06c9e742297f..43082704a7cb120df5db68bf511625ef11126a65 100644 (file)
--- a/doc/src/sgml/ecpg.sgml
+++ b/doc/src/sgml/ecpg.sgml
@@ -2390,9 +2390,10 @@ int PGTYPESnumeric_to_long(numeric *nv, long *lp);
        The function converts the numeric value from the variable that
        nv points to into the long integer variable that
        lp points to. It returns 0 on success and -1 if an error
-       occurs, including overflow. On overflow, the global variable
+       occurs, including overflow and underflow. On overflow, the global variable
        errno will be set to PGTYPES_NUM_OVERFLOW
-       additionally.
+       and on underflow errno will be set to
+       PGTYPES_NUM_UNDERFLOW.