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Simplify memory management for regex DFAs a little. 

Coverity complained that functions in regexec.c might leak DFA
storage.  It's wrong, but this logic is confusing enough that it's
not so surprising Coverity couldn't make sense of it.  Rewrite
in hopes of making it more legible to humans as well as machines.
This commit is contained in:
Tom Lane 2021-02-21 20:29:11 -05:00
parent 6ee479abfc
commit 190c79884a
2 changed files with 13 additions and 11 deletions
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18
src/backend/regex/rege_dfa.c
View File

@ -499,7 +499,7 @@ newdfa(struct vars *v,
struct dfa *d; struct dfa *d;
size_t nss = cnfa->nstates * 2; size_t nss = cnfa->nstates * 2;
int wordsper = (cnfa->nstates + UBITS - 1) / UBITS; int wordsper = (cnfa->nstates + UBITS - 1) / UBITS;
struct smalldfa *smallwas = sml; bool ismalloced = false;
assert(cnfa != NULL && cnfa->nstates != 0); assert(cnfa != NULL && cnfa->nstates != 0);
@ -514,6 +514,7 @@ newdfa(struct vars *v,
ERR(REG_ESPACE); ERR(REG_ESPACE);
return NULL; return NULL;
} }
ismalloced = true;
} }
d = &sml->dfa; d = &sml->dfa;
d->ssets = sml->ssets; d->ssets = sml->ssets;
@ -521,8 +522,8 @@ newdfa(struct vars *v,
d->work = &d->statesarea[nss]; d->work = &d->statesarea[nss];
d->outsarea = sml->outsarea; d->outsarea = sml->outsarea;
d->incarea = sml->incarea; d->incarea = sml->incarea;
d->cptsmalloced = 0; d->ismalloced = ismalloced;
d->mallocarea = (smallwas == NULL) ? (char *) sml : NULL; d->arraysmalloced = false; /* not separately allocated, anyway */
} }
else else
{ {
@ -540,8 +541,9 @@ newdfa(struct vars *v,
sizeof(struct sset *)); sizeof(struct sset *));
d->incarea = (struct arcp *) MALLOC(nss * cnfa->ncolors * d->incarea = (struct arcp *) MALLOC(nss * cnfa->ncolors *
sizeof(struct arcp)); sizeof(struct arcp));
d->cptsmalloced = 1; d->ismalloced = true;
d->mallocarea = (char *) d; d->arraysmalloced = true;
/* now freedfa() will behave sanely */
if (d->ssets == NULL || d->statesarea == NULL || if (d->ssets == NULL || d->statesarea == NULL ||
d->outsarea == NULL || d->incarea == NULL) d->outsarea == NULL || d->incarea == NULL)
{ {
@ -573,7 +575,7 @@ newdfa(struct vars *v,
static void static void
freedfa(struct dfa *d) freedfa(struct dfa *d)
{ {
if (d->cptsmalloced) if (d->arraysmalloced)
{ {
if (d->ssets != NULL) if (d->ssets != NULL)
FREE(d->ssets); FREE(d->ssets);
@ -585,8 +587,8 @@ freedfa(struct dfa *d)
FREE(d->incarea); FREE(d->incarea);
} }
if (d->mallocarea != NULL) if (d->ismalloced)
FREE(d->mallocarea); FREE(d);
} }
/* /*

6
src/backend/regex/regexec.c
View File

@ -77,8 +77,8 @@ struct dfa
chr *lastpost; /* location of last cache-flushed success */ chr *lastpost; /* location of last cache-flushed success */
chr *lastnopr; /* location of last cache-flushed NOPROGRESS */ chr *lastnopr; /* location of last cache-flushed NOPROGRESS */
struct sset *search; /* replacement-search-pointer memory */ struct sset *search; /* replacement-search-pointer memory */
int cptsmalloced; /* were the areas individually malloced? */ bool ismalloced; /* should this struct dfa be freed? */
char *mallocarea; /* self, or master malloced area, or NULL */ bool arraysmalloced; /* should its subsidiary arrays be freed? */
}; };
#define WORK 1 /* number of work bitvectors needed */ #define WORK 1 /* number of work bitvectors needed */
@ -88,7 +88,7 @@ struct dfa
#define FEWCOLORS 15 #define FEWCOLORS 15
struct smalldfa struct smalldfa
{ {
struct dfa dfa; struct dfa dfa; /* must be first */
struct sset ssets[FEWSTATES * 2]; struct sset ssets[FEWSTATES * 2];
unsigned statesarea[FEWSTATES * 2 + WORK]; unsigned statesarea[FEWSTATES * 2 + WORK];
struct sset *outsarea[FEWSTATES * 2 * FEWCOLORS]; struct sset *outsarea[FEWSTATES * 2 * FEWCOLORS];