Stdlib: file_get_contents() offset/length args return false — must read slice (ext/standard/file.c)

[PurHur]

Category

stdlib · php-src-strict

Problem

file_get_contents($path, false, null, $offset, $length) must return a substring of the file bytes starting at $offset for at most $length bytes. Zend returns the slice on readable local files; this compiler returns false for the 5-argument form even when the path is valid and readable.

Single-argument and no-offset forms work; failure is specific to $offset + $length operands.

php-src reference

• php/php-src ext/standard/file.c — PHP_FUNCTION(file_get_contents) (offset, maxlen / $length)
• php/php-src ext/standard/streams.c — stream read with offset

Repro (failure today — verified 2026-06-19)

test/repro/maintainer_file_get_contents_offset.php (or inline):

<?php
declare(strict_types=1);
$slice = file_get_contents(__FILE__, false, null, 0, 10);
var_export($slice);
echo "\n";
$mid = file_get_contents(__FILE__, false, null, 5, 5);
var_export($mid);
echo "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/repro/maintainer_file_get_contents_offset.php
php bin/vm.php test/repro/maintainer_file_get_contents_offset.php
'

Probe	Zend PHP 8.2	VM today
file_get_contents(__FILE__, false, null, 0, 10)	first 10 bytes (e.g. '<?php\nvar_')	false ❌
file_get_contents(__FILE__, false, null, 5, 5)	5-byte mid slice	false ❌
file_get_contents(__FILE__)	full file	OK

Scope (PHP-in-PHP first)

Path	Work
ext/standard/file_get_contents.php	Honor $offset + $length in PHP read helper
ext/standard/VmFs.php / stream read	Seek + bounded read; reject only on real I/O failure
lib/JIT/Builtin/FileGetContents.php	Mirror slice semantics or defer with matrix note
Tests	test/compliance/cases/stdlib/file_get_contents_offset_length.phpt

Forbidden: new slice logic in runtime/*.c — port php-src behavior into ext/standard.

Done when (php-src-strict)

• Both repro slices match Zend byte-for-byte on VM
• $offset beyond file length → false / empty string per Zend (document which)
• file_get_contents() with stream context + offset still works
• JIT/AOT match or capability matrix updated
• ./script/ci-fast.sh --filter file_get_contents_offset green

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter file_get_contents_offset 2>/dev/null || true'

Related

• Stdlib: file_get_contents() filename: named parameter rejected (ext/standard/file.c) #10045 named filename: param · Stdlib: stream_context_set_options() inline array literal — $options arrives null (ext/standard/streams.c) #10056 stream_context inline literal · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

Status check (2026-06-19): offset/length slice repro appears fixed on master:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php -r "var_export(file_get_contents(\"/etc/hostname\", false, null, 0, 3));"
php bin/vm.php -r "var_export(file_get_contents(\"/etc/hostname\", false, null, 0, 3));"'
# both: '\''1e9'\''

Close candidate after compliance PHPT lands. Named filename: gap tracked separately in #10045.

[PurHur]

claim: PHP Compiler STD Lib — AOT link for file_get_contents() (__compiler_file_get_contents undefined at link time; VM green, AotTest file_get_contents* failing)

[PurHur]

WIP handoff (branch agent/stdlib-file-get-contents-aot-link):

Root cause: Type/String_.php returns early for LOAD_TYPE_STANDALONE (#13571), so StringFileGetContents::implement() never runs during user-script AOT init — __compiler_file_get_contents stays a link stub.

Fix in progress:

• Register StringFileGetContents + StringReadfile in Context::ensureMinimalUserStandaloneBodies()
• Save/restore LLVM insert block during bridge emit (StreamReadRuntime pattern)
• Restore thin libc open/read bridge (StringFileGetContentsLibc) gated on user-script/bootstrap AOT when nested PHP JIT is unavailable (php-in-php: __compiler_file_get_contents JIT via FileGetContentsJitHelper PHP — drop open/read LLVM (#1492) #15309)

Verification (green):

source script/php-env.sh
unset PHP_COMPILER_AOT_USER_SCRIPT
php bin/compile.php -o /tmp/fgc_aot - <<'PHP'
<?php
$path = 'test/compliance/cases/stdlib/readfile_fixture/data.txt';
echo file_get_contents($path);
PHP
/tmp/fgc_aot
# hello readfile

vendor/bin/phpunit test/compliance/JITTest.php --filter file_get_contents
vendor/bin/phpunit test/unit/FileGetContentsRuntimeShrinkTest.php

Still red:

• vendor/bin/phpunit test/aot/AotTest.php --filter file_get_contents — compile links but run aborts munmap_chunk(): invalid pointer when PHPUnit drives compile via proc_open (direct php bin/compile.php OK). Needs follow-up.
• file_get_contents_offset AOT fixture — compile segfault (139); needs __compiler_file_put_contents link + offset slice path.
• readfile AOT — returns 0 (needs StringReadfileLibc parity).

[PurHur]

Merged via #16710 — user-script AOT links __compiler_file_get_contents (libc bridge for minimal standalone init). AOT fixture file_get_contents.phpt green; offset/maxlen AOT still blocked on file_put_contents standalone link.