Unexpected return values: strcmp(), strncmp(), strcasecmp(), strncasecmp about doc-en HOT 6 CLOSED

I'm confused about the documentation note.
I found 0bc9241334eaebd737eb0455e9739257e74d0713, which introduced the wrong note...

What changed is the return value when lengths differ.
In that case there was a bugfix in php/php-src#8220 so that it's now guaranteed to be smaller than 0 (-1), 0 or greater than 0 (1) if the length difference of two strings is greater than 2 GB.

The behaviour of strcmp & co is unchanged for strings where lengths match.

General question: Do we fix wrong notes in UPGRADING after the release?

from doc-en.

What changed is the return value when lengths differ.

Except that's not quite true either. https://3v4l.org/GUuA5

strcmp uses zend_binary_strcmp, whose relevant bit is

	retval = memcmp(s1, s2, MIN(len1, len2));
	if (!retval) {
		return ZEND_THREEWAY_COMPARE(len1, len2);
	} else {
		return retval;
	}

It will memcmp using the smaller length of the two strings (comparing a "prefix", so to speak) and if they're different then it returns whatever that value is - which is only guaranteed to be negative/positive [1]. If the two prefixes are the same, only then will it go to ZEND_THREEWAY_COMPARE, and that's the part which explicitly returns -1/0/+1 based on which string is shorter.
https://3v4l.org/mT8di

So the implementation of the "always returns -1/0/+1" feature missed out on normalizing memcmp's return value.

[1] On Windows, I always get -1/+1. And 3v4l's live preview (which is WASM and currently only on PHP 8.1) also returns -1/+1. And it sounds like valgrind may also substitute its own memcmp that returns only -1/+1.

from doc-en.

Yeah, I wasn't 100% precise in specifying the exact circumstances. What I really wanted to say is that there was no intent in normalizing that value, just that the change fixes the integer overflow for size differences >2GB.

from doc-en.

@bwoebi I think it makes sense to fix the migration page in the docs.
https://www.php.net/manual/en/migration82.other-changes.php#migration82.other-changes.functions.core

But more importantly, the docs themselves are also wrong.

https://www.php.net/manual/en/function.strcmp.php

Returns -1 if string1 is less than string2; 1 if string1 is greater than string2, and 0 if they are equal.

I'm moving this to the docs repo.

from doc-en.

I checked again by using the official docker image from https://hub.docker.com/_/php on my Linux machine. I used the changed test script from https://3v4l.org/GUuA5 and only added the output of phpversion().

I get the same result as on my machine:

PHP: 8.2.16
int(-4)
int(4)
int(-4)
int(4)
int(-4)
int(4)
int(-4)
int(4)

The page 3v4l.org may has some issues by itself, maybe...

However, I also tested it on a different machine with Window 11 installed and with the packages:

• php-8.2.16-Win32-vs16-x64.zip
• php-8.2.16-nts-Win32-vs16-x64.zip

For both, comparing to my machine/Linux, I get a different, but regarding the return values -1, 0, 1 also "wrong" result:

int(-1)
int(1)
int(-4)
int(4)
int(-1)
int(1)
int(-4)
int(4)

So, I would assume that it isn't only a "wrong documentation" topic..

from doc-en.

While there looks to be some dispute over whether this is a docs of core bug above; surely it can be removed from the docs for now?

This is quite a serious inaccuracy as the docs led me to believe code should target === -1|0|1.

from doc-en.