PHP RFC: 64 bit platform improvements for string length and integer in zval

• Version: 2.3
• Date: 2014-05-06
• Authors: Anatol Belski ab@php.net, Matt Ficken mattficken@php.net, Stephen A. Zarkos szarkos@php.net
• Status: Accepted
• First published at: https://wiki.php.net/rfc/size_t_and_int64

Current PHP zval datatype implementation uses long datatype to handle signed integer and int datatype to handle string length. The most 64 bit capable platforms PHP is used on are LP64 (Linux/most Unix-like), LLP64 (Windows), ILP64 (SPARC64). The data model used in PHP for the relevant datatypes on those platforms looks as follows

Regarding PHP that means today, even on 64 bit platforms the following features lack on consistency

• handling of strings >= 2^31
• handling of 64 bit integers
• large file support
• handling of numeric 64 bit hash keys

Thus, the current situation contains a roadblock on the way to the overall consistent 64 bit platforms support and further improvement of PHP.

To bring everything inline, a dynamic types model is being suggested. Besides the platform inconsistency elimination, this will enable several further moves (see the Future scope). Performance improvements for 64 bit platforms, just to name one, could be then the subject of a new RFC and would have the base for the further development.

The following datatypes are suggested for use in zval

Those datatypes are guaranteed to be 64 bit which makes PHP work consistent on any 64 bit platforms. The usage of this datatypes is integrated into the appropriate places across PHP. The size of zval, with default field alignment, is expected to grow by 4 bytes on LLP64 platforms only.

For the consistent LFS support, a set of portable datatypes and macros was invented and integrated.

For consistent 64 bit numeric hash keys support, the appropriate 64 bit unsigned was integrated.

The usage of long datatype continues on 32 bit platforms. The only change there is the usage of size_t for the string length (which is effectively a 32 bit unsigned).

No further configure options are needed, the platform and compiler will be automatically recognized and an appropriate set of datatypes and macros will be activated.

• Zend/zend_int.h
• Zend/zend_types.h
• Zend/zend_stream.h
• main/php_streams.h

Generally speaking, every occurence mentioning “long” in macros or function names should be replaced with a corresponding neutral keyword, suggested “int”, in further like “lval” with “ival”, etc.

Johannes Schlüter did a great work on developing a clang plugin allowing static analyze of the zpp calls. Steps was undertaken to make it available on windows as well.

New spprintf modifier 'p' was implemented to platform independently output php_int_t datatype. That modifier can be used with 'd', 'u', 'x' and 'o' printf format specs with spprintf, snprintf and the wrapping printf implementations.

This modifier is of course available in all the spprintf/snprintf derivatives. Any of the introduced new datatypes can be used with the appropriate format spec.

• long and int in zval have to be replaced with the new integer datatypes
• code working with hashes and arrays has to use php_uint_t
• code working with filesystem objects has to use appropriate portable macros and datatypes
• code working with string lengths has to predominatly use php_size_t
• 'l', 'L', 's', 'p' parameter formats aren't available anymore
• Z_STRLEN*, *LONG*, etc. older macros aren't available anymore

PHP6 (or whatever next major is called)

• possible collisions with dependency libraries using 32 bit integer datatypes (range checks needed)
• existing extensions have to adapt zend_parsing_parameters() format
• existing extensions have to use new APIs and macros for string length and integer
• in the user space some function names need to be adapted on the new semantics, for instance long2ip() should be int2ip()

Some dead SAPIs are present in the core. They was not ported. A decision based on whether the authors are willing to support them has to be met. Then porting or removal of those SAPIs can be scheduled. The separate RFC https://wiki.php.net/rfc/removal_of_dead_sapis was created to handle this issue.

It has to do with squeezing anything possible from the 64 bit platforms, for maximal PHP benefit. No real features are going to be changed, removed or added to the PHP language.

Performance test done on the base of master and str_size_and_int64 can be found here http://windows.php.net/downloads/snaps/ostc/pftt/perf/results-20140411-masterr6c2f7bc-str_size_and_int64raa0c920.html. There is no performance difference between two (between 0-2%).

/*

The numbers here are the test scores one already might have seen in the other performance tests.

*, ** Some issues with the x64 versions of 5.5.8 and str_size_and_int64 when testing with opcache enabled. However issues of this kind are well known on windows (for instance #64926) and are due to some unluckily choosen memory address. So the cause persists in the mainstream and is not because of this patch. \\*/

Tutorial, tools and compatibility header to ease the migration of the PECL extensions are available. The goal is to make the same source in the new semantic compatible with older PHP versions.

	php_int_t i0, i1;
	char *s0, p0;
	php_size_t s0_len, p0_len;
 
	if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "iISP", &i0, &i1, &s0, &s0_len, &p0, &p0_len) == FAILURE) {
		return;
	}

	php_int_t i0;
 
	if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "i", &i0) == FAILURE) {
		return;
	}
 
	if (INT_MAX < i0 || INT_MIN > i0) {
		php_error_docref(NULL TSRMLS_CC, E_WARNING, "Value '" ZEND_INT_FMT "' is out of range", i0);
		return;
	}

	php_error_docref(NULL TSRMLS_CC, E_WARNING, "Value '%pd' is out of range", i0);

	char *s0;
	php_size_t s0_len;
	php_int_t max_len;
 
	if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "Si", &s0, &s0_len, &max_len) == FAILURE) {
		return;
	}
 
	if (max_len >= 0 && s0_len > max_len) {
		return;
	}

char *dup_substr(zval *s, zval *i)
{
	php_size_t len;
	php_int_t max;
	char ret;
 
	convert_to_string(s);
	convert_to_int(i);
 
	len = Z_STRSIZE_P(s);
	max = Z_IVAL(i);
 
	if (max < 0 || max >= 0 && max > len)
	{
	return NULL;
	}
 
	ret = emalloc((max + 1) * sizeof(char));
 
	if (!ret) {
		return NULL;
	}
 
	memmove(ret, Z_STRVAL_P(s), max);
	ret[max] = '\0';
 
	return ret;
}

• in far perspective - easier to implement 128 bit support
• in near perspective - excellent base for 64 bit performance optimization
• easier integration on rarely used platforms
• easier integration on new platforms

Accept this RFC for PHP6 (or whatever next major is called)
Real name	Yes	No
ab (ab)
adobkin (adobkin)
ajf (ajf)
andi (andi)
arpad (arpad)
auroraeosrose (auroraeosrose)
bjori (bjori)
brianlmoon (brianlmoon)
bwoebi (bwoebi)
chobieeee (chobieeee)
chx (chx)
crodas (crodas)
danielc (danielc)
datibbaw (datibbaw)
davey (davey)
derick (derick)
dm (dm)
dmitry (dmitry)
felipe (felipe)
frozenfire (frozenfire)
googleguy (googleguy)
guilhermeblanco (guilhermeblanco)
gwynne (gwynne)
iliaa (iliaa)
indeyets (indeyets)
jedibc (jedibc)
jpauli (jpauli)
jwage (jwage)
kalle (kalle)
klaussilveira (klaussilveira)
krakjoe (krakjoe)
kriscraig (kriscraig)
laruence (laruence)
levim (levim)
lstrojny (lstrojny)
malukenho (malukenho)
mattficken (mattficken)
mbeccati (mbeccati)
nikic (nikic)
pajoye (pajoye)
philip (philip)
rasmus (rasmus)
salathe (salathe)
szarkos (szarkos)
thorstenr (thorstenr)
treffynnon (treffynnon)
tyrael (tyrael)
uw (uw)
yohgaki (yohgaki)
zeev (zeev)
zhangzhenyu (zhangzhenyu)
Final result:	28	23
This poll has been closed.

Merge strategy
Real name	after the vote, master	phpng
ab (ab)
adobkin (adobkin)
ajf (ajf)
andrey (andrey)
auroraeosrose (auroraeosrose)
bjori (bjori)
brianlmoon (brianlmoon)
bwoebi (bwoebi)
chobieeee (chobieeee)
chx (chx)
crodas (crodas)
davey (davey)
derick (derick)
dm (dm)
dmitry (dmitry)
googleguy (googleguy)
guilhermeblanco (guilhermeblanco)
gwynne (gwynne)
iliaa (iliaa)
indeyets (indeyets)
jedibc (jedibc)
jgmdev (jgmdev)
jpauli (jpauli)
jwage (jwage)
kalle (kalle)
klaussilveira (klaussilveira)
krakjoe (krakjoe)
kriscraig (kriscraig)
laruence (laruence)
levim (levim)
lstrojny (lstrojny)
malukenho (malukenho)
mattficken (mattficken)
mbeccati (mbeccati)
nicolas (nicolas)
nikic (nikic)
pajoye (pajoye)
philip (philip)
philstu (philstu)
pollita (pollita)
rasmus (rasmus)
salathe (salathe)
stas (stas)
szarkos (szarkos)
thorstenr (thorstenr)
tony2001 (tony2001)
treffynnon (treffynnon)
tyrael (tyrael)
uw (uw)
Final result:	17	40
This poll has been closed.

The RFC is considered approved with 50%+1 acceptance.
The vote starts on May 13th 2014 and ends on May 20th 2014 due to the issues with the mailing lists, the vote period is extended till May 26th 2014.

Feature branch
Backport branch of PHP 5.6 (for comparisons only)
Windows builds
Test reports

Patch progress page
PECL porting docs'n'tools

Initial discussion brought up by Anthony Ferrara
Discussion after implementation start
Discussions of the previous RFC version

After the project is implemented, this section should contain

1. the version(s) it was merged to
2. a link to the git commit(s)
3. a link to the PHP manual entry for the feature

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