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/regcomp.c b/src/backend/regex/regcomp.c
index 44a472fa69e77cb4efccceacc05b9bdbfb09516c..5f1e3c5a1a64894962fb1583c33fd6cf6fcbaabc 100644 (file)
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -228,7 +228,7 @@ struct vars
    struct subre *tree;         /* subexpression tree */
    struct subre *treechain;    /* all tree nodes allocated */
    struct subre *treefree;     /* any free tree nodes */
-   int         ntree;          /* number of tree nodes */
+   int         ntree;          /* number of tree nodes, plus one */
    struct cvec *cv;            /* interface cvec */
    struct cvec *cv2;           /* utility cvec */
    struct subre *lacons;       /* lookahead-constraint vector */

diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c
index 5e78f8149c8783291b489a8db980d417e314f46d..b4a3dc3ab4038949eea242892c6dcf02a0aa9624 100644 (file)
--- a/src/backend/regex/regexec.c
+++ b/src/backend/regex/regexec.c
@@ -348,7 +348,11 @@ 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)

diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 2f3be1aa0ae22c52c14368f4dad9079376841ca7..dac0403311946656921d3e35c7ed9564c074d5a7 100644 (file)
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -470,7 +470,7 @@ struct guts
    size_t      nsub;           /* copy of re_nsub */
    struct subre *tree;
    struct cnfa search;         /* for fast preliminary search */
-   int         ntree;          /* number of subre's, less one */
+   int         ntree;          /* number of subre's, plus one */
    struct colormap cmap;
    int         FUNCPTR(compare, (const chr *, const chr *, size_t));
    struct subre *lacons;       /* lookahead-constraint vector */