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1 | =head1 NAME |
2 | |
3 | perltodo - Perl TO-DO List |
4 | |
5 | =head1 DESCRIPTION |
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6 | |
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7 | This is a list of wishes for Perl. Send updates to |
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8 | I<perl5-porters@perl.org>. If you want to work on any of these |
9 | projects, be sure to check the perl5-porters archives for past ideas, |
10 | flames, and propaganda. This will save you time and also prevent you |
11 | from implementing something that Larry has already vetoed. One set |
12 | of archives may be found at: |
13 | |
14 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
15 | |
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16 | =head1 assertions |
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17 | |
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18 | Clean up and finish support for assertions. See L<assertions>. |
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19 | |
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20 | =head1 iCOW |
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21 | |
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22 | Sarathy and Arthur have a proposal for an improved Copy On Write which |
23 | specifically will be able to COW new ithreads. If this can be implemented |
24 | it would be a good thing. |
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25 | |
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26 | =head1 (?{...}) closures in regexps |
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27 | |
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28 | Fix (or rewrite) the implementation of the C</(?{...})/> closures. |
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29 | |
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30 | =head1 A re-entrant regexp engine |
31 | |
32 | This will allow the use of a regex from inside (?{ }), (??{ }) and |
33 | (?(?{ })|) constructs. |
34 | |
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35 | =head1 pragmata |
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36 | |
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37 | =head2 lexical pragmas |
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38 | |
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39 | Reimplement the mechanism of lexical pragmas to be more extensible. Fix |
40 | current pragmas that don't work well (or at all) with lexical scopes or in |
41 | run-time eval(STRING) (C<sort>, C<re>, C<encoding> for example). MJD has a |
42 | preliminary patch that implements this. |
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43 | |
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44 | =head2 use less 'memory' |
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45 | |
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46 | Investigate trade offs to switch out perl's choices on memory usage. |
47 | Particularly perl should be able to give memory back. |
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48 | |
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49 | =head1 prototypes and functions |
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50 | |
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51 | =head2 _ prototype character |
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52 | |
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53 | Study the possibility of adding a new prototype character, C<_>, meaning |
54 | "this argument defaults to $_". |
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55 | |
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56 | =head2 inlining autoloaded constants |
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57 | |
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58 | Currently the optimiser can inline constants when expressed as subroutines |
59 | with prototype ($) that return a constant. Likewise, many packages wrapping |
60 | C libraries export lots of constants as subroutines which are AUTOLOADed on |
61 | demand. However, these have no prototypes, so can't be seen as constants by |
62 | the optimiser. Some way of cheaply (low syntax, low memory overhead) to the |
63 | perl compiler that a name is a constant would be great, so that it knows to |
64 | call the AUTOLOAD routine at compile time, and then inline the constant. |
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65 | |
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66 | =head2 Finish off lvalue functions |
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67 | |
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68 | The old perltodo notes "They don't work in the debugger, and they don't work for |
69 | list or hash slices." |
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70 | |
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71 | =head1 Unicode and UTF8 |
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72 | |
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73 | =head2 Implicit Latin 1 => Unicode translation |
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74 | |
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75 | Conversions from byte strings to UTF-8 currently map high bit characters |
76 | to Unicode without translation (or, depending on how you look at it, by |
77 | implicitly assuming that the byte strings are in Latin-1). As perl assumes |
78 | the C locale by default, upgrading a string to UTF-8 may change the |
79 | meaning of its contents regarding character classes, case mapping, etc. |
80 | This should probably emit a warning (at least). |
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81 | |
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82 | =head2 UTF8 caching code |
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83 | |
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84 | The string position/offset cache is not optional. It should be. |
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85 | |
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86 | =head2 Unicode in Filenames |
87 | |
88 | chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, |
89 | opendir, qx, readdir, readlink, rename, rmdir, stat, symlink, sysopen, |
90 | system, truncate, unlink, utime, -X. All these could potentially accept |
91 | Unicode filenames either as input or output (and in the case of system |
92 | and qx Unicode in general, as input or output to/from the shell). |
93 | Whether a filesystem - an operating system pair understands Unicode in |
94 | filenames varies. |
95 | |
96 | Known combinations that have some level of understanding include |
97 | Microsoft NTFS, Apple HFS+ (In Mac OS 9 and X) and Apple UFS (in Mac |
98 | OS X), NFS v4 is rumored to be Unicode, and of course Plan 9. How to |
99 | create Unicode filenames, what forms of Unicode are accepted and used |
100 | (UCS-2, UTF-16, UTF-8), what (if any) is the normalization form used, |
101 | and so on, varies. Finding the right level of interfacing to Perl |
102 | requires some thought. Remember that an OS does not implicate a |
103 | filesystem. |
104 | |
105 | (The Windows -C command flag "wide API support" has been at least |
106 | temporarily retired in 5.8.1, and the -C has been repurposed, see |
107 | L<perlrun>.) |
108 | |
109 | =head2 Unicode in %ENV |
110 | |
111 | Currently the %ENV entries are always byte strings. |
112 | |
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113 | =head1 Regexps |
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114 | |
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115 | =head2 regexp optimiser optional |
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116 | |
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117 | The regexp optimiser is not optional. It should configurable to be, to allow |
118 | its performance to be measured, and its bugs to be easily demonstrated. |
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119 | |
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120 | =head2 common suffices/prefices in regexps (trie optimization) |
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121 | |
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122 | Currently, the user has to optimize C<foo|far> and C<foo|goo> into |
123 | C<f(?:oo|ar)> and C<[fg]oo> by hand; this could be done automatically. |
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124 | |
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125 | =head1 POD |
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126 | |
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127 | =head2 POD -> HTML conversion still sucks |
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128 | |
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129 | Which is crazy given just how simple POD purports to be, and how simple HTML |
130 | can be. |
131 | |
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132 | =head1 Misc medium sized projects |
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133 | |
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134 | =head2 UNITCHECK |
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135 | |
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136 | Introduce a new special block, UNITCHECK, which is run at the end of a |
137 | compilation unit (module, file, eval(STRING) block). This will correspond to |
138 | the Perl 6 CHECK. Perl 5's CHECK cannot be changed or removed because the |
139 | O.pm/B.pm backend framework depends on it. |
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140 | |
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141 | =head2 optional optimizer |
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142 | |
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143 | Make the peephole optimizer optional. |
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144 | |
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145 | =head2 You WANT *how* many |
146 | |
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147 | Currently contexts are void, scalar and list. split has a special mechanism in |
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148 | place to pass in the number of return values wanted. It would be useful to |
149 | have a general mechanism for this, backwards compatible and little speed hit. |
150 | This would allow proposals such as short circuiting sort to be implemented |
151 | as a module on CPAN. |
152 | |
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153 | =head2 lexical aliases |
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154 | |
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155 | Allow lexical aliases (maybe via the syntax C<my \$alias = \$foo>. |
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156 | |
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157 | =head2 no 6 |
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158 | |
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159 | Make C<no 6> and C<no v6> work (opposite of C<use 5.005>, etc.). |
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160 | |
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161 | =head2 IPv6 |
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162 | |
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163 | Clean this up. Check everything in core works |
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164 | |
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165 | =head2 entersub XS vs Perl |
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166 | |
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167 | At the moment pp_entersub is huge, and has code to deal with entering both |
168 | perl and and XS subroutines. Subroutine implementations rarely change between |
169 | perl and XS at run time, so investigate using 2 ops to enter subs (one for |
170 | XS, one for perl) and swap between if a sub is redefined. |
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171 | |
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172 | =head2 @INC source filter to Filter::Simple |
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173 | |
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174 | The second return value from a sub in @INC can be a source filter. This isn't |
175 | documented. It should be changed to use Filter::Simple, tested and documented. |
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176 | |
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177 | =head2 bincompat functions |
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178 | |
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179 | There are lots of functions which are retained for binary compatibility. |
180 | Clean these up. Move them to mathom.c, and don't compile for blead? |
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181 | |
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182 | =head2 Use fchown/fchmod internally |
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183 | |
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184 | The old perltodo notes "This has been done in places, but needs a thorough |
185 | code review. Also fchdir is available in some platforms." |
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186 | |
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187 | =head2 Constant folding |
188 | |
189 | The peephole optimiser should trap errors during constant folding, and give |
190 | up on the folding, rather than bailing out at compile time. It is quite |
191 | possible that the unfoldable constant is in unreachable code, eg something |
192 | akin to C<$a = 0/0 if 0;> |
193 | |
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194 | =head1 Tests |
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195 | |
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196 | =head2 Make Schwern poorer |
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197 | |
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198 | Tests for everything, At which point Schwern coughs up $500 to TPF. |
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199 | |
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200 | =head2 test B |
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201 | |
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202 | A test suite for the B module would be nice. |
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203 | |
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204 | =head2 common test code for timed bailout |
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205 | |
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206 | Write portable self destruct code for tests to stop them burning CPU in |
207 | infinite loops. Needs to avoid using alarm, as some of the tests are testing |
208 | alarm/sleep or timers. |
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209 | |
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210 | =head1 Installation |
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211 | |
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212 | =head2 compressed man pages |
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213 | |
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214 | Be able to install them |
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215 | |
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216 | =head2 Make Config.pm cope with differences between build and installed perl |
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217 | |
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218 | =head2 Relocatable perl |
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219 | |
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220 | Make it possible to create a relocatable perl binary. Will need some collusion |
221 | with Config.pm. We could use a syntax of ... for location of current binary? |
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222 | |
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223 | =head2 make HTML install work |
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224 | |
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225 | =head2 put patchlevel in -v |
226 | |
227 | Currently perl from p4/rsync ships with a patchlevel.h file that usually |
228 | defines one local patch, of the form "MAINT12345" or "RC1". The output of |
229 | perl -v doesn't report that a perl isn't an official release, and this |
230 | information can get lost in bugs reports. Because of this, the minor version |
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231 | isn't bumped up until RC time, to minimise the possibility of versions of perl |
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232 | escaping that believe themselves to be newer than they actually are. |
233 | |
234 | It would be useful to find an elegant way to have the "this is an interim |
235 | maintenance release" or "this is a release candidate" in the terse -v output, |
236 | and have it so that it's easy for the pumpking to remove this just as the |
237 | release tarball is rolled up. This way the version pulled out of rsync would |
238 | always say "I'm a development release" and it would be safe to bump the |
239 | reported minor version as soon as a release ships, which would aid perl |
240 | developers. |
241 | |
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242 | =head1 Incremental things |
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243 | |
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244 | Some tasks that don't need to get done in one big hit. |
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245 | |
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246 | =head2 autovivification |
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247 | |
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248 | Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict; |
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249 | |
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250 | =head2 fix tainting bugs |
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251 | |
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252 | Fix the bugs revealed by running the test suite with the C<-t> switch (via |
253 | C<make test.taintwarn>). |
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254 | |
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255 | =head2 Make tainting consistent |
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256 | |
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257 | Tainting would be easier to use if it didn't take documented shortcuts and allow |
258 | taint to "leak" everywhere within an expression. |
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259 | |
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260 | =head2 Dual life everything |
261 | |
262 | As part of the "dists" plan, anything that doesn't belong in the smallest perl |
263 | distribution needs to be dual lifed. Anything else can be too. |
264 | |
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265 | =head1 Vague things |
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266 | |
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267 | Some more nebulous ideas |
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268 | |
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269 | =head2 threads |
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270 | |
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271 | Make threads more robust. |
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272 | |
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273 | =head2 POSIX memory footprint |
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274 | |
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275 | Ilya observed that use POSIX; eats memory like there's no tomorrow, and at |
276 | various times worked to cut it down. There is probably still fat to cut out - |
277 | for example POSIX passes Exporter some very memory hungry data structures. |
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278 | |
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279 | =head2 Optimize away @_ |
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280 | |
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281 | The old perltodo notes "Look at the "reification" code in C<av.c>". |
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282 | |
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283 | =head2 switch ops |
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284 | |
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285 | The old perltodo notes "Although we have C<Switch.pm> in core, Larry points to |
286 | the dormant C<nswitch> and C<cswitch> ops in F<pp.c>; using these opcodes would |
287 | be much faster." |
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288 | |
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289 | =head2 Attach/detach debugger from running program |
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290 | |
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291 | The old perltodo notes "With C<gdb>, you can attach the debugger to a running |
292 | program if you pass the process ID. It would be good to do this with the Perl |
293 | debugger on a running Perl program, although I'm not sure how it would be done." |
294 | ssh and screen do this with named pipes in tmp. Maybe we can too. |
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295 | |
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296 | =head2 A decent benchmark |
297 | |
298 | perlbench seems impervious to any recent changes made to the perl core. It would |
299 | be useful to have a reasonable general benchmarking suite that roughly |
300 | represented what current perl programs do, and measurably reported whether |
301 | tweaks to the core improve, degrade or don't really affect performance, to |
302 | guide people attempting to optimise the guts of perl. |
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303 | |
304 | =head2 readpipe(LIST) |
305 | |
306 | system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid |
307 | running a shell. readpipe() (the function behind qx//) could be similarly |
308 | extended. |
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309 | |
310 | =head2 Self ties |
311 | |
312 | self ties are currently illegal because they caused too many segfaults. Maybe |
313 | the causes of these could be tracked down and self-ties on all types re- |
314 | instated. |