Non-traditional, Line by Line Compilation in Perl

[sumeetgrover]

This might have been previously found, but very interesting to know that the compilation carried out by Perl through the perl -c is non-traditional. In C, compilation would throw out all the syntax errors at once since the compiler would read through the entire code.

Interesting to discover that Perl compilation / parse tree building is line by line, therefore, on a 100 line program, if an error was encountered on line 10, the message thrown out by the compiler is:
failed--compilation aborted at MyModule.pm line 10
Therefore, one must not assume that line 10 was the only error that exists in the Perl module. Once the error is fixed on line 10, be prepared to see more subsequent syntax errors, if they exist.

[Anonymous Monk]

is line by line

Not quite, more likely, its statement oriented (as opposed to expression)

• What is the difference between a Statement and an Expression?
• perldoc compile
• perldoc perlcompile
• Execution order of END/CHECK vs BEGIN/INIT
• INIT blocks and runtime code loading
• What is an INIT block?
• CHECK and INIT under mod_perl
• BEGIN, END, eval and die.
• eval() and INIT{}
• Which phase am I in?

[Anonymous Monk]

Example, all oneliners :D

$ perl -c -e " use strict; use warnings; BEGIN { $sumeet = 1; } $grove
+r = 1; } "
Global symbol "$sumeet" requires explicit package name at -e line 1.
BEGIN not safe after errors--compilation aborted at -e line 1.

$ perl -c -e " use strict; use warnings; BEGIN { our $sumeet = 1; } $g
+rover = 1; } "
Global symbol "$grover" requires explicit package name at -e line 1.
Unmatched right curly bracket at -e line 1, at end of line
syntax error at -e line 1, near "; }"
-e had compilation errors.

$ perl -c -e " use strict; use warnings; BEGIN { our $sumeet = 1; } $g
+rover = 1; "
Global symbol "$grover" requires explicit package name at -e line 1.
-e had compilation errors.

$ perl -c -e " use strict; use warnings; BEGIN { our $sumeet = 1; } ou
+r $grover = 1; "
-e syntax OK

[sumeetgrover]

Agreed, compilation would be based on statements, separated by semicolon!

[Anonymous Monk]

Agreed, compilation would be based on statements, separated by semicolon!

We don't need no stinkin semicolons !:)

$ perl -c -e " use strict; use warnings; { $foo = 1 } { $bar }} "
Global symbol "$foo" requires explicit package name at -e line 1.
Global symbol "$bar" requires explicit package name at -e line 1.
Unmatched right curly bracket at -e line 1, at end of line
syntax error at -e line 1, near "}}"
-e had compilation errors.

$ perl -e " use strict; use warnings;  { our $foo = 1 } { our $bar } p
+rint 666"
666

[JavaFan]

I do not think you are correct.

    $  (echo '};'; echo '{};'; echo '};') | perl -c
    Unmatched right curly bracket at - line 1, at end of line
    syntax error at - line 1, near "}"
    Unmatched right curly bracket at - line 3, at end of line
    syntax error at - line 3, near "}"
    - had compilation errors.
    $

Parsing did not stop at finding the first syntax error.

[choroba]

Should I ever get engaged in C compiling, I would try to remember :-)

[ambrus]

It's certainly not what you want, but can someone help me? is compiled line by line. :-)