Fix calculation of aligned buffer size

[cmb69]

As is, for requested size which are already aligned, we over-allocate.

This issue has been reported by @kkmuffme.

[arnaud-lb]

LGTM

[iluuu1994]

Looks correct to me. Thanks!

[kkmuffme]

Will this also fix it for the php.ini output_buffering directive, if that has the same issue?

EDIT: will this ship with PHP 8.4? or will it also be backported to earlier PHP versions?

[cmb69]

Will this also fix it for the php.ini output_buffering directive, if that has the same issue?

Yes, that uses the same code, so has the same issue, and will be fixed as well.

will this ship with PHP 8.4? or will it also be backported to earlier PHP versions?

Unlikely, since at least in a strict sense, this patch constitutes an ABI break.

[kkmuffme]

Unlikely, since at least in a strict sense, this patch constitutes an ABI break.

Unlikely that it's backported?
Or unlikely it ships with PHP 8.4?
Or both unlikely?

[kkmuffme]

Will this also fix it for the php.ini output_buffering directive, if that has the same issue?
Yes, that uses the same code, so has the same issue, and will be fixed as well.

Just to add on to this then to clarify this (and get some feedback if there might be an issue):
for the php.ini directive:
output_buffering=0 => off, behaves like chunk_size 1
output_buffering=1 => on, behaves like chunk_size 0
output_buffering=2 (or higher value) => on, behaves like chunk_size 2 (or higher value)

This might be something that should perhaps be clarified in the docs, as it's an easy mistake to make when switching between .ini and PHP

[cmb69]

Or both unlikely?

Both are unlikely; introducing an ABI is already too late for PHP 8.4, so this fix should probably only get into PHP 8.5 (or 9.0, whatever comes next).

Just to add on to this then to clarify this (and get some feedback if there might be an issue): for the php.ini directive: output_buffering=0 => off, behaves like chunk_size 1 output_buffering=1 => on, behaves like chunk_size 0 output_buffering=2 (or higher value) => on, behaves like chunk_size 2 (or higher value)

This might be something that should perhaps be clarified in the docs, as it's an easy mistake to make when switching between .ini and PHP

Oh, good catch! Since there is special handling for 0 and 1

php-src/main/main.c

Lines 1862 to 1863 in 95fa39d

	} else if (PG(output_buffering)) {
	php_output_start_user(NULL, PG(output_buffering) > 1 ? PG(output_buffering) : 0, PHP_OUTPUT_HANDLER_STDFLAGS);

we should document that.