Line 13 manipulates the flags; since we've changed the PV, any IV or NV
values will no longer be valid: if we have C<$a=10; $a.="6";> we don't
-want to use the old IV of 10. C<SvPOK_only_utf8> is a special UTF8-aware
+want to use the old IV of 10. C<SvPOK_only_utf8> is a special UTF-8-aware
version of C<SvPOK_only>, a macro which turns off the IOK and NOK flags
and turns on POK. The final C<SvTAINT> is a macro which launders tainted
data if taint mode is turned on.
print Perl_sv_2pv_nolen(sv)
+=back
+
You may find it helpful to have a "macro dictionary", which you can
produce by saying C<cpp -dM perl.c | sort>. Even then, F<cpp> won't
recursively apply those macros for you.
means configuring with C<-Doptimize=-g3>. Other compilers might use a
different switch (if they support debugging macros at all).
-=back
-
=head2 Dumping Perl Data Structures
One way to get around this macro hell is to use the dumping functions in
on and create a simple patch. Here's something Larry suggested: if a
C<U> is the first active format during a C<pack>, (for example,
C<pack "U3C8", @stuff>) then the resulting string should be treated as
-UTF8 encoded.
+UTF-8 encoded.
How do we prepare to fix this up? First we locate the code in question -
the C<pack> happens at runtime, so it's going to be in one of the F<pp>
while (pat < patend) {
Now if we see a C<U> which was at the start of the string, we turn on
-the UTF8 flag for the output SV, C<cat>:
+the C<UTF8> flag for the output SV, C<cat>:
+ if (datumtype == 'U' && pat==patcopy+1)
+ SvUTF8_on(cat);
=item *
If the pattern begins with a C<U>, the resulting string will be treated
- as Unicode-encoded. You can force UTF8 encoding on in a string with an
- initial C<U0>, and the bytes that follow will be interpreted as Unicode
- characters. If you don't want this to happen, you can begin your pattern
- with C<C0> (or anything else) to force Perl not to UTF8 encode your
+ as UTF-8-encoded Unicode. You can force UTF-8 encoding on in a string
+ with an initial C<U0>, and the bytes that follow will be interpreted as
+ Unicode characters. If you don't want this to happen, you can begin your
+ pattern with C<C0> (or anything else) to force Perl not to UTF-8 encode your
string, and then follow this with a C<U*> somewhere in your pattern.
All done. Now let's create the patch. F<Porting/patching.pod> tells us
meant as a guide to interfacing these tools with Perl, not
as any kind of guide to the use of the tools themselves.
-Note that running under memory debuggers such as Purify, valgrind,
-or Third Degree greatly slows down the execution: seconds become minutes,
-minutes become hours.
+B<NOTE 1>: Running under memory debuggers such as Purify, valgrind, or
+Third Degree greatly slows down the execution: seconds become minutes,
+minutes become hours. For example as of Perl 5.8.1, the
+ext/Encode/t/Unicode.t takes extraordinarily long to complete under
+e.g. Purify, Third Degree, and valgrind. Under valgrind it takes more
+than six hours, even on a snappy computer-- the said test must be
+doing something that is quite unfriendly for memory debuggers. If you
+don't feel like waiting, that you can simply kill away the perl
+process.
+
+B<NOTE 2>: To minimize the number of memory leak false alarms (see
+L</PERL_DESTRUCT_LEVEL> for more information), you have to have
+environment variable PERL_DESTRUCT_LEVEL set to 2. The F<TEST>
+and harness scripts do that automatically. But if you are running
+some of the tests manually-- for csh-like shells:
+
+ setenv PERL_DESTRUCT_LEVEL 2
+
+and for Bourne-type shells:
+
+ PERL_DESTRUCT_LEVEL=2
+ export PERL_DESTRUCT_LEVEL
+
+or in UNIXy environments you can also use the C<env> command:
+
+ env PERL_DESTRUCT_LEVEL=2 valgrind ./perl -Ilib ...
+
+B<NOTE 3>: There are known memory leaks when there are compile-time
+errors within eval or require, seeing C<S_doeval> in the call stack
+is a good sign of these. Fixing these leaks is non-trivial,
+unfortunately, but they must be fixed eventually.
=head2 Rational Software's Purify
optimal testing with Purify. Purify is available under
Windows NT, Solaris, HP-UX, SGI, and Siemens Unix.
-The only currently known leaks happen when there are
-compile-time errors within eval or require. (Fixing these
-is non-trivial, unfortunately, but they must be fixed
-eventually.)
-
=head2 Purify on Unix
On Unix, Purify creates a new Perl binary. To get the most
This binary is used in place of the standard 'perl' binary
when you want to debug Perl memory problems.
-To minimize the number of memory leak false alarms
-(see L</PERL_DESTRUCT_LEVEL>), set environment variable
-PERL_DESTRUCT_LEVEL to 2.
-
- setenv PERL_DESTRUCT_LEVEL 2
-
-In Bourne-type shells:
-
- PERL_DESTRUCT_LEVEL=2
- export PERL_DESTRUCT_LEVEL
-
As an example, to show any memory leaks produced during the
standard Perl testset you would create and run the Purify'ed
perl as:
which would instrument Perl in memory, run Perl on test.pl,
then finally report any memory problems.
-B<NOTE>: as of Perl 5.8.0, the ext/Encode/t/Unicode.t takes
-extraordinarily long (hours?) to complete under Purify. It has been
-theorized that it would eventually finish, but nobody has so far been
-patient enough :-) (This same extreme slowdown has been seen also with
-the Third Degree tool, so the said test must be doing something that
-is quite unfriendly for memory debuggers.) It is suggested that you
-simply kill away that testing process.
-
=head2 valgrind
The excellent valgrind tool can be used to find out both memory leaks
and illegal memory accesses. As of August 2003 it unfortunately works
only on x86 (ELF) Linux. The special "test.valgrind" target can be used
-to run the tests under valgrind. Note that in the test script (t/TEST)
-currently (as of Perl 5.8.1) only naughty memory accesses are logged,
-not memory leaks. Found errors are logged in files named F<test.valgrind>.
-Also note that with Perl built with ithreads, the glibc (at least 2.2.5)
-seems to have a bug of its own, where a non-locked POSIX mutex is
-unlocked, and valgrind catches this, for every test-- therefore the
-test script ignores that error.
+to run the tests under valgrind. Found errors and memory leaks are
+logged in files named F<test.valgrind>.
+
+As system libraries (most notably glibc) are also triggering errors,
+valgrind allows to suppress such errors using suppression files. The
+default suppression file that comes with valgrind already catches a lot
+of them. Some additional suppressions are defined in F<t/perl.supp>.
To get valgrind and for more information see
=head2 PERL_DESTRUCT_LEVEL
-If you want to run any of the tests yourself manually using the
-pureperl or perl.third executables, please note that by default
-perl B<does not> explicitly cleanup all the memory it has allocated
-(such as global memory arenas) but instead lets the exit() of
-the whole program "take care" of such allocations, also known
-as "global destruction of objects".
+If you want to run any of the tests yourself manually using e.g.
+valgrind, or the pureperl or perl.third executables, please note that
+by default perl B<does not> explicitly cleanup all the memory it has
+allocated (such as global memory arenas) but instead lets the exit()
+of the whole program "take care" of such allocations, also known as
+"global destruction of objects".
There is a way to tell perl to do complete cleanup: set the
environment variable PERL_DESTRUCT_LEVEL to a non-zero value.
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