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Document race issue for pcre2_code_free() after serialize/deserialize.

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Philip.Hazel 2015-11-03 18:40:28 +00:00
parent 2caf22dc61
commit 3e24a1b351
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doc/pcre2serialize.3
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@ -1,4 +1,4 @@
.TH PCRE2SERIALIZE 3 "20 January 2015" "PCRE2 10.10"
.TH PCRE2SERIALIZE 3 "03 November 2015" "PCRE2 10.21"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.SH "SAVING AND RE-USING PRECOMPILED PCRE2 PATTERNS"
@ -22,12 +22,12 @@ If you are running an application that uses a large number of regular
expression patterns, it may be useful to store them in a precompiled form
instead of having to compile them every time the application is run. However,
if you are using the just-in-time optimization feature, it is not possible to
save and reload the JIT data, because it is position-dependent. In addition,
the host on which the patterns are reloaded must be running the same version of
PCRE2, with the same code unit width, and must also have the same endianness,
pointer width and PCRE2_SIZE type. For example, patterns compiled on a 32-bit
system using PCRE2's 16-bit library cannot be reloaded on a 64-bit system, nor
can they be reloaded using the 8-bit library.
save and reload the JIT data, because it is position-dependent. The host on
which the patterns are reloaded must be running the same version of PCRE2, with
the same code unit width, and must also have the same endianness, pointer width
and PCRE2_SIZE type. For example, patterns compiled on a 32-bit system using
PCRE2's 16-bit library cannot be reloaded on a 64-bit system, nor can they be
reloaded using the 8-bit library.
.
.
.SH "SAVING COMPILED PATTERNS"
@ -139,10 +139,15 @@ PCRE2_ERROR_BADMAGIC may mean that the data is corrupt, or that it was compiled
on a system with different endianness.
.P
Decoded patterns can be used for matching in the usual way, and must be freed
by calling \fBpcre2_code_free()\fP as normal. A single copy of the character
tables is used by all the decoded patterns. A reference count is used to
by calling \fBpcre2_code_free()\fP. However, be aware that there is a potential
race issue if you are using multiple patterns that were decoded from a single
byte stream in a multithreaded application. A single copy of the character
tables is used by all the decoded patterns and a reference count is used to
arrange for its memory to be automatically freed when the last pattern is
freed.
freed, but there is no locking on this reference count. Therefore, if you want
to call \fBpcre2_code_free()\fP for these patterns in different threads, you
must arrange your own locking, and ensure that \fBpcre2_code_free()\fP cannot
be called by two threads at the same time.
.P
If a pattern was processed by \fBpcre2_jit_compile()\fP before being
serialized, the JIT data is discarded and so is no longer available after a
@ -165,6 +170,6 @@ Cambridge, England.
.rs
.sp
.nf
Last updated: 20 January 2015
Last updated: 03 November 2015
Copyright (c) 1997-2015 University of Cambridge.
.fi