skip test with libpcre2 10.38

[remicollet]

With libpcre2 10.38

TEST FAILURE: ../ext/pcre/tests/bug70345.diff --
001+ Warning: preg_split(): Compilation failed: \K is not allowed in lookarounds (but see PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK) at offset 9 in /builddir/build/BUILD/php-8.0.12RC1/ext/pcre/tests/bug70345.php on line 5
     bool(false)
     
004+ Warning: preg_match(): Compilation failed: \K is not allowed in lookarounds (but see PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK) at offset 12 in /builddir/build/BUILD/php-8.0.12RC1/ext/pcre/tests/bug70345.php on line 9
005+ NULL
003- Warning: preg_match(): Get subpatterns list failed in %s on line %d
004- array(0) {
005- }

This is for 7.4
Probably a better fix is possible in 8.1+ defined some new constant to manage this \K modifier using PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK

[nikic]

Setting the flag seems like the right option, to preserve BC.

[cmb69]

Maybe set the flag for 8.1 and earlier, but not for master? According to the PCRE2 docs it is "somewhat dangerous".

[remicollet]

Maybe set the flag for 8.1 and earlier, but not for master? According to the PCRE2 docs it is "somewhat dangerous".

I agree, but we perhaps also have to expose this flag to users ?

[nikic]

Does anyone know what the "somewhat dangerous" there actually means?

[cmb69]

Does anyone know what the "somewhat dangerous" there actually means?

PCRE2Project/pcre2#4 (comment) explains it.

[nikic]

Okay, so the problem is that some uses of pcre2_match() in conjunction with this feature may result in an infinite loop -- the question would then be whether this affects our particular usage.

[remicollet]

See pr #7602 (7.4) and pr #7603 (8.0+)