diff options
| author | Jarkko Hietaniemi <jhi@iki.fi> | 2006-07-17 12:09:24 +0300 |
|---|---|---|
| committer | Rafael Garcia-Suarez <rgarciasuarez@gmail.com> | 2006-07-18 21:43:52 +0000 |
| commit | bc028b6b7f0f25fba45e10fa46e3fe91dbe9a76d (patch) | |
| tree | 7c8832aa8af9ba27e527ad1c2f640827b68bb4e0 /pod | |
| parent | f782ee33d0f49cb1ee007e3e83d1f175efc6fdc1 (diff) | |
| download | perl-bc028b6b7f0f25fba45e10fa46e3fe91dbe9a76d.tar.gz | |
make magic vtables const if PERL_GLOBAL_STRUCT_PRIVATE
Message-ID: <44BB2994.5090609@iki.fi>
p4raw-id: //depot/perl@28599
Diffstat (limited to 'pod')
| -rw-r--r-- | pod/perlguts.pod | 6 | ||||
| -rw-r--r-- | pod/perlhack.pod | 13 |
2 files changed, 15 insertions, 4 deletions
diff --git a/pod/perlguts.pod b/pod/perlguts.pod index a39c8f9cbc..bbf8742d97 100644 --- a/pod/perlguts.pod +++ b/pod/perlguts.pod @@ -1914,6 +1914,12 @@ please see F<miniperlmain.c> for usage details. You may also need to use C<dVAR> in your coding to "declare the global variables" when you are using them. dTHX does this for you automatically. +To see whether you have non-const data you can use a BSD-compatible C<nm>: + + nm libperl.a | grep -v ' [TURtr] ' + +If this displays any C<D> or C<d> symbols, you have non-const data. + For backward compatibility reasons defining just PERL_GLOBAL_STRUCT doesn't actually hide all symbols inside a big global struct: some PerlIO_xxx vtables are left visible. The PERL_GLOBAL_STRUCT_PRIVATE diff --git a/pod/perlhack.pod b/pod/perlhack.pod index f2109bb6bd..efa3344394 100644 --- a/pod/perlhack.pod +++ b/pod/perlhack.pod @@ -2404,9 +2404,9 @@ therefore more ways for things to go wrong. You should try it. Introducing (non-read-only) globals Do not introduce any modifiable globals, truly global or file static. -They are bad form and break multithreading. The right way is to -introduce them as new interpreter variables, see F<intrpvar.h> (at the -very end for binary compatibility). +They are bad form and complicate multithreading and other forms of +concurrency. The right way is to introduce them as new interpreter +variables, see F<intrpvar.h> (at the very end for binary compatibility). Introducing read-only (const) globals is okay, as long as you verify with e.g. C<nm libperl.a|egrep -v ' [TURtr] '> (if your C<nm> has @@ -2417,12 +2417,17 @@ If you want to have static strings, make them constant: static const char etc[] = "..."; -If you want to have arrays of static strings, note carefully +If you want to have arrays of constant strings, note carefully the right combination of C<const>s: static const char * const yippee[] = {"hi", "ho", "silver"}; +There is a way to completely hide any modifiable globals (they are all +moved to heap), the compilation setting C<-DPERL_GLOBAL_STRUCT_PRIVATE>. +It is not normally used, but can be used for testing, read more +about it in L<perlhack>. + =item * Not exporting your new function |