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Diffstat (limited to 'README.lexwarn')
| -rw-r--r-- | README.lexwarn | 244 |
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diff --git a/README.lexwarn b/README.lexwarn deleted file mode 100644 index 27e5ec810c..0000000000 --- a/README.lexwarn +++ /dev/null @@ -1,244 +0,0 @@ -Date: 29th July 1998 - -This patch adds lexical warnings to Perl. It should apply over -5.005_50 - -NOTE: This is a prototype. Do not assume that lexical warnings will - necessarily be anything like this implementation. - -Changes -======= - - Date: 8th April 1998 - - * patch now applies cleanly over 5.004_64 - - * added the -X switch (the inverse "lint" command) - - Date: 26th Feb 1997 - - * By popular demand, the warnings bitmask can now be of arbitrary - length. The code uses an SV* to store the bitmask. - - * Rationalised the warning categories a bit. This area still needs - a lot of work. - - * Added -W switch (the "lint" command). - - * Added an experimental feature to allow warnings to be excalated - to fatal errors. - - -The "use warning" pragma -======================== - - The "use warning" pragma is intended to replace both the use of the - command line flag "-w" and its equivalent variable $^W with a pragma - that works like the existing "strict" pragma. - - This means that the scope of the pragma is limited to the enclosing - block. It also means that that a pragma setting will not leak across - files (via use/require/do). This will allow authors to define the - degree of warning checks that will be applied to their module. - - By default warnings are disabled. - - All warnings are enabled in a block by either of these: - - use warning ; - use warning 'all' ; - - Similarly all warnings are disabled in a block by either of these: - - no warning ; - no warning 'all' ; - - A hierarchy of "categories" have been defined to allow groups of - warnings to be enabled/disabled in isolation. The current - hierarchy is: - - all - +--- unsafe -------+--- taint - | | - | +--- substr - | | - | +--- signal - | | - | +--- closure - | | - | +--- untie - | - +--- io ---------+--- pipe - | | - | +--- unopened - | | - | +--- closed - | | - | +--- newline - | | - | +--- exec - | - +--- syntax ----+--- ambiguous - | | - | +--- semicolon - | | - | +--- precedence - | | - | +--- reserved - | | - | +--- octal - | | - | +--- parenthesis - | | - | +--- deprecated - | - |--- uninitialized - | - +--- void - | - +--- recursion - | - +--- redefine - | - +--- numeric - | - +--- once - | - +--- misc - - This hierarchy is very tentative. Feedback is needed. - - Just like the "strict" pragma any of these categories can be - combined - - use warning qw(void redefine) ; - no warning qw(io syntax untie) ; - -The "lint" flag, -W -=================== - -If the -W flag is used on the command line, it will enable all warnings -throughout the program regardless of whether warnings were disabled -locally using "no warning" or $^W =0. This includes any file that gets -included during compilation via use/require. - -The inverse "lint" flag, -X -=========================== -Does exactly the same as the -W flag, except it disables all warnings. - - -Backward Compatability -====================== - - How Lexical Warnings interact with -w/$^W - - 1. The -w flag just sets the global $^W variable as in 5.004 - This means that any legacy code that currently relies on - manipulating $^W to control warning behaviour will still work. - - 2. Apart from now being a boolean, the $^W variable operates in - exactly the same horrible uncontrolled global way as in 5.004, - except... - - 3. If a piece of code is under the control of a lexical warning - pragma, the $^W variable will be ignored. - - The combined effect of 2 & 3 is that it will will allow new code - which will use the lexical warning pragma to control old - $^W-type code (using a local $^W=0) if it really wants to, but - not vice-versa. - - 4. The only way to override a lexical warnings setting is with the - new -W or -X command line flags. - - -Fatal Warnings -============== - -This feature is very experimental. - -The presence of the word "FATAL" in the category list will escalate any -warnings from the category specified that are detected in the lexical -scope into fatal errors. In the code below, there are 3 places where a -deprecated warning will be detected, the middle one will produce a -fatal error. - - - use warning ; - - $a = 1 if $a EQ $b ; - - { - use warning qw(FATAL deprecated) ; - $a = 1 if $a EQ $b ; - } - - $a = 1 if $a EQ $b ; - - -TODO -==== - -test harness for -X (assuming it is a permanent fixture). -win32, os2 & vms all have warnings. These need to be included. - -Unresolved Issues -================= - - The pragma name? - A few possibilities: - warning - warnings - warn - - Hierarchy of Warnings - The current patch has a fairly arbitrary hierarchy. - Ideas for a useful hierarchy would be most welcome. - - A command line option to turn off all warnings? - -X or -q, perhaps. - - Current mandatory warnings. - May be useful to bring them under the control of this pragma. - - Severity - Do we want/need a severity classification? - pedantic - high/strict/precise - medium/default - low/common - - Versions - This is a thorhy issue. Say someone writes a script using Perl - 5.004 and places this at the top: - - use warning ; - - Time passes and 5.005 comes out. It has added a few extra warnings. - The script prints warning messages. - - A possibility is to allow the warnings that are checked to be - limited to those available in a given version of Perl. A possible - syntax could be: - - use warning 5.004 ; - - or - - use warning 5.004 qw(void uninitialized) ; - - Do we really need this amount of control? - - Documentation - There isn't any yet. - - - perl5db.pl - The debugger saves and restores $^W at runtime. I haven't checked - whether the debugger will still work with the lexical warnings - patch applied. - - diagnostics.pm - I *think* I've got diagnostics to work with the lexiacal warnings - patch, but there were design decisions made in diagnostics to work - around the limitations of $^W. Now that those limitations are gone, - the module should be revisited. |