Modifying the Compiler

[Irobeth]

Modifying the Compiler

Postby irobeth on Sat Jul 25, 2009 6:55 pm
I'm trying to modify the compiler/tokenizer/language parser to allow
support for new keywords like unless / until

a) Is this even supported? There isn't documentation that I can find
anywhere official about how the compiler works or how to extend it, to
my knowledge.

b) I'm hitting a roadblock with a test for unless following the guide
at this website using 5.3.0, I have checked over and over to make sure
my code is like the examples but am being presented with:

Code: Select all
---- EXPECTED OUTPUT
unless FALSE is TRUE, this is printed
---- ACTUAL OUTPUT
Parse error: syntax error, unexpected '{' in {my path}php-5.3.0/
Zend/tests/unless.php on line 2
---- FAILED



for the test

Code: Select all
--TEST--
unless statement
--FILE--
<?php
unless(FALSE) {
print 'unless FALSE is TRUE, this is printed';
}
unless(TRUE) {
print 'unless TRUE is TRUE, this is printed';
}
?>
--EXPECT--
unless FALSE is TRUE, this is printed



Below are snippets relevant to this test:

===========================================================
zend_language_scanner.l :

<ST_IN_SCRIPTING>"if" {
return T_IF;
}

<ST_IN_SCRIPTING>"unless" {
return T_UNLESS;
}

<ST_IN_SCRIPTING>"elseif" {
return T_ELSEIF;
}

===========================================================

===========================================================
zend_language_parser.y :

%token T_DIR
%token T_NS_SEPARATOR
%token T_UNLESS

snip...

unticked_statement:
'{' inner_statement_list '}'
| T_IF '(' expr ')' { zend_do_if_cond(&$3, &$4
TSRMLS_CC); } statement { zend_do_if_after_statement(&$4, 1
TSRMLS_CC); } elseif_list else_single { zend_do_if_end(TSRMLS_C); }
| T_UNLESS '(' expr ')' { zend_do_unless_cond(&$3, &
$4 TSRMLS_CC); } statement { zend_do_if_after_statement(&$4, 1
TSRMLS_CC); } { zend_do_if_end(TSRMLS_C); }
===========================================================

===========================================================
zend_compile.h

void zend_do_if_cond(const znode *cond, znode
*closing_bracket_token TSRMLS_DC);
void zend_do_unless_cond(const znode *cond, znode
*closing_bracket_token TSRMLS_DC);
void zend_do_if_after_statement(const znode
*closing_bracket_token, unsigned char initialize TSRMLS_DC);
void zend_do_if_end(TSRMLS_D);
===========================================================

===========================================================
zend_compile.c

void zend_do_unless_cond(const znode *cond, znode
*closing_bracket_token TSRMLS_DC)
{
int unless_cond_op_number = get_next_op_number(CG
(active_op_array));
zend_op *opline = get_next_op(CG(active_op_array)
TSRMLS_CC);

opline->opcode = ZEND_JMPNZ;
opline->op1 = *cond;
closing_bracket_token->u.opline_num =
unless_cond_op_number;
SET_UNUSED(opline->op2);
INC_BPC(CG(active_op_array));
}
===========================================================


After making these changes and running make test, the output is:


=====================================================================
Running selected tests.
FAIL unless statement [Zend/tests/unless.phpt]

=====================================================================
Number of tests : 1 1
Tests skipped : 0 ( 0.0%) --------
Tests warned : 0 ( 0.0%) ( 0.0%)
Tests failed : 1 (100.0%) (100.0%)
Expected fail : 0 ( 0.0%) ( 0.0%)
Tests passed : 0 ( 0.0%) ( 0.0%)

---------------------------------------------------------------------
Time taken : 0 seconds

=====================================================================


=====================================================================
FAILED TEST SUMMARY

---------------------------------------------------------------------
unless statement [Zend/tests/unless.phpt]

=====================================================================



So clearly something is wrong, but what? Is modification of the
compiler just not something that's meant to be?

[Bastian Feder]

do you know Sebastian Bergmans' presentation?
http://www.slideshare.net/sebastian_bergmann/php-compiler-internals

hf
bastian

--
spread the word ... see www.browsehappy.com ;o)
Calvin: Weekends don't count unless you spend them doing something
completely pointless.

[Irobeth]

I have, this is where I started.

On Aug 13, 11:22 am, Bastian Feder <bastian.fe...@gmail.com> wrote:
> do you know Sebastian Bergmans' presentation?http://www.slideshare.net/sebastian_bergmann/php-compiler-internals