Re: Detecting undefined subroutines at compile time

Perl detects undeclared subs (which is better than detecting undefined subs) at compile-time if you omit parens on sub calls.

>perl -c -e"use strict; sub f {} f;"
-e syntax OK

>perl -c -e"use strict; sub f;   f;"
-e syntax OK

>perl -c -e"use strict;          f;"
Bareword "f" not allowed while "strict subs" in use at -e line 1.
-e had compilation errors.

>perl -c -e"use strict; sub g {}  g 'abc';"
-e syntax OK

>perl -c -e"use strict;           g 'abc';"
String found where operator expected at -e line 1, near "g 'abc'"
        (Do you need to predeclare g?)
syntax error at -e line 1, near "g 'abc'"
-e had compilation errors.
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Omitting parens on sub calls causes a whole of weird stuff, so I recommend against doing this.

Comment on Re: Detecting undefined subroutines at compile time Download Code

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Re^2: Detecting undefined subroutines at compile time by Anonymous Monk on May 04, 2011 at 17:07 UTC
Omitting parens on sub calls causes a whole of of weird stuff, The hard evidence in your post completely contradicts your premature summation. I see clear, consise error messages.	[reply]
Re^3: Detecting undefined subroutines at compile time by ikegami (Patriarch) on May 04, 2011 at 18:59 UTC
Evidence that it does work at finding undeclared functions does not contradict the claim that omitting parens in function calls introduces problems. The main problem is that unary "+" or equivalent must be used in a number of places, and forgetting to do causes bugs. These are not always caught at compile-time, and they can be subtle. Another problem is misleading error messages. Three issues from omitted parens came up here and/or on stack-overflow in the last month, but I don't remember them.	[reply]