Fix low-probability memory leak in regex execution.

After an internal failure in shortest() or longest() while pinning down the
exact location of a match, find() forgot to free the DFA structure before
returning.  This is pretty unlikely to occur, since we just successfully
ran the "search" variant of the DFA; but it could happen, and it would
result in a session-lifespan memory leak since this code uses malloc()
directly.  Problem seems to have been aboriginal in Spencer's library,
so back-patch all the way.

In passing, correct a thinko in a comment I added awhile back about the
meaning of the "ntree" field.

I happened across these issues while comparing our code to Tcl's version
of the library.

diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index 6135f59f22b110db90665a7c6ac10dbe8ed2be2a..6e2adf5cac07158f2fc8f95cd8f6e97979ffbcff 100644 (file)
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -323,7 +323,11 @@ find(struct vars * v,
                           (chr **) NULL, &hitend);
        else
            end = longest(v, d, begin, v->stop, &hitend);
-       NOERR();
+       if (ISERR())
+       {
+           freedfa(d);
+           return v->err;
+       }
        if (hitend && cold == NULL)
            cold = begin;
        if (end != NULL)