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Ensure ovector[0,1] are both PCRE2_UNSET during callouts.

This commit is contained in:
Philip.Hazel 2017-04-14 12:39:41 +00:00
parent e8cdae3c5b
commit 106028089e
2 changed files with 27 additions and 18 deletions
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19
doc/pcre2callout.3
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@ -1,4 +1,4 @@
.TH PCRE2CALLOUT 3 "29 March 2017" "PCRE2 10.30" .TH PCRE2CALLOUT 3 "14 April 2017" "PCRE2 10.30"
.SH NAME .SH NAME
PCRE2 - Perl-compatible regular expressions (revised API) PCRE2 - Perl-compatible regular expressions (revised API)
.SH SYNOPSIS .SH SYNOPSIS
@ -191,8 +191,8 @@ callouts such as the example above are obeyed.
.rs .rs
.sp .sp
During matching, when PCRE2 reaches a callout point, if an external function is During matching, when PCRE2 reaches a callout point, if an external function is
set in the match context, it is called. This applies to both normal and DFA provided in the match context, it is called. This applies to both normal and
matching. The first argument to the callout function is a pointer to a DFA matching. The first argument to the callout function is a pointer to a
\fBpcre2_callout\fP block. The second argument is the void * callout data that \fBpcre2_callout\fP block. The second argument is the void * callout data that
was supplied when the callout was set up by calling \fBpcre2_set_callout()\fP was supplied when the callout was set up by calling \fBpcre2_set_callout()\fP
(see the (see the
@ -261,7 +261,7 @@ The remaining fields in the callout block are the same for both kinds of
callout. callout.
.P .P
The \fIoffset_vector\fP field is a pointer to a vector of capturing offsets The \fIoffset_vector\fP field is a pointer to a vector of capturing offsets
(the "ovector"). You may read certain elements in this vector, but you must not (the "ovector"). You may read the elements in this vector, but you must not
change any of them. change any of them.
.P .P
For calls to \fBpcre2_match()\fP, the \fIoffset_vector\fP field is not (since For calls to \fBpcre2_match()\fP, the \fIoffset_vector\fP field is not (since
@ -281,10 +281,11 @@ for example, when the callout in the pattern ((a)(b))(?C2) is taken,
.P .P
The contents of ovector[2] to ovector[<capture_top>*2-1] can be inspected in The contents of ovector[2] to ovector[<capture_top>*2-1] can be inspected in
order to extract substrings that have been matched so far, in the same way as order to extract substrings that have been matched so far, in the same way as
extracting substrings after a match has completed. The values in ovector[0] and extracting substrings after a match has completed. The values in ovector[0] and
ovector[1] are undefined and should not be used in any way. Substrings that ovector[1] are always PCRE2_UNSET because the match is by definition not
have not been captured (but whose numbers are less than \fIcapture_top\fP) have complete. Substrings that have not been captured but whose numbers are less
both of their ovector slots set to PCRE2_UNSET. than \fIcapture_top\fP also have both of their ovector slots set to
PCRE2_UNSET.
.P .P
For DFA matching, the \fIoffset_vector\fP field points to the ovector that was For DFA matching, the \fIoffset_vector\fP field points to the ovector that was
passed to the matching function in the match data block, but it holds no useful passed to the matching function in the match data block, but it holds no useful
@ -410,6 +411,6 @@ Cambridge, England.
.rs .rs
.sp .sp
.nf .nf
Last updated: 29 March 2017 Last updated: 14 April 2017
Copyright (c) 1997-2017 University of Cambridge. Copyright (c) 1997-2017 University of Cambridge.
.fi .fi

26
src/pcre2_match.c
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@ -263,20 +263,14 @@ Returns: the return from the callout
static int static int
do_callout(heapframe *F, match_block *mb, PCRE2_SIZE *lengthptr) do_callout(heapframe *F, match_block *mb, PCRE2_SIZE *lengthptr)
{ {
PCRE2_SIZE save0, save1;
pcre2_callout_block cb; pcre2_callout_block cb;
int rc;
*lengthptr = (*Fecode == OP_CALLOUT)? *lengthptr = (*Fecode == OP_CALLOUT)?
PRIV(OP_lengths)[OP_CALLOUT] : GET(Fecode, 1 + 2*LINK_SIZE); PRIV(OP_lengths)[OP_CALLOUT] : GET(Fecode, 1 + 2*LINK_SIZE);
if (mb->callout == NULL) return 0; /* No callout function provided */ if (mb->callout == NULL) return 0; /* No callout function provided */
/* The original matching code (pre 10.40) worked directly with the ovector
passed by the user, and this was passed to callouts. Now that the working
ovector is in the backtracking frame, it no longer needs to reserve space for
the overall match offsets (which would waste space in the frame). For backward
compatibility, however, we pass capture_top and offset_vector to the callout as
if for the extended ovector. */
cb.version = 1; cb.version = 1;
cb.capture_top = (uint32_t)Foffset_top/2 + 1; cb.capture_top = (uint32_t)Foffset_top/2 + 1;
cb.capture_last = Fcapture_last; cb.capture_last = Fcapture_last;
@ -304,8 +298,22 @@ else /* String callout */
cb.callout_string_length = cb.callout_string_length =
*lengthptr - (1 + 4*LINK_SIZE) - 2; *lengthptr - (1 + 4*LINK_SIZE) - 2;
} }
/* The original matching code (pre 10.30) worked directly with the ovector
passed by the user, and this was passed to callouts. Now that the working
ovector is in the backtracking frame, it no longer needs to reserve space for
the overall match offsets (which would waste space in the frame). For backward
compatibility, however, we pass capture_top and offset_vector to the callout as
if for the extended ovector, and we ensure that the first two slots are unset
by preserving and restoring their current contents. */
return mb->callout(&cb, mb->callout_data); save0 = Fovector[-2];
save1 = Fovector[-1];
Fovector[-2] = Fovector[-1] = PCRE2_UNSET;
rc = mb->callout(&cb, mb->callout_data);
Fovector[-2] = save0;
Fovector[-1] = save1;
return rc;
} }