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Stdlib: ob_get_contents()/ob_get_length()/ob_end_clean() — JIT/AOT lowering (phase 2 of #3236) #4914

Closed
#17653
Closed
Stdlib: ob_get_contents()/ob_get_length()/ob_end_clean() — JIT/AOT lowering (phase 2 of #3236)#4914
#17653
Labels
area:compilerCompiler / CFG / JITarea:vmVirtual machineenhancementNew feature or requestimplementation-readySpec complete: repro, php-src ref, done-when — safe for workers to claimphase-4:stdlibPhase 4 – stdlib for web apps

Description

@PurHur
PurHur
opened on Jun 3, 2026

Category

stdlib · runtime

Problem

Output-buffer read/discard builtins (ob_get_contents, ob_get_length, ob_end_clean) are VM-only (LogicException in JIT call()), although VM parity landed in #3236. Scripts compiled with JIT/AOT cannot use the OB stack API without VM fallback.

php-src reference

Repro

<?php
ob_start();
echo 'x';
var_export(ob_get_contents());
var_export(ob_get_length());
var_export(ob_end_clean());
HARNESS_DOCKER_RUN_OPTS='--memory=8g --cpus=2' ./script/docker-exec.sh -- bash -lc '
  source script/php-env.sh
  php bin/jit.php -r "ob_start(); echo \"x\"; var_export(ob_get_contents());"
'
Mode ob_get_contents() after ob_start(); echo x;
Zend / VM 'x'
JIT LogicException: ob_get_contents() is VM-only in this compiler build

Same for ob_get_length() and ob_end_clean() (ext/standard/ob_*.php).

Scope (this repo)

Area Files
VM ext/standard/VmOb.php (existing stack)
JIT ext/standard/ob_get_contents.php, ob_get_length.php, ob_end_clean.php — implement call() via shared helper (see JitObGetFlush.php)
AOT compliance .phpt under test/fixtures/aot/cases/
Matrix script/capability-matrix.php notes

Done when

Links

Activity

  1. PurHur
    added
    enhancementNew feature or request
    phase-4:stdlibPhase 4 – stdlib for web apps
    area:compilerCompiler / CFG / JIT
    area:vmVirtual machine
    implementation-readySpec complete: repro, php-src ref, done-when — safe for workers to claim
    on Jun 3, 2026

  2. PurHur commented on Jun 13, 2026

    @PurHur
    PurHur
    on Jun 13, 2026
    OwnerAuthor

    claim: PHP Compiler STD Lib — starting this run

  3. PurHur commented on Jun 13, 2026

    @PurHur
    PurHur
    on Jun 13, 2026
    OwnerAuthor

    Unclaiming: ob_get_contents()/ob_get_length()/ob_end_clean() JIT/AOT already green on master. JitObGetContents/JitObGetLength/JitObEndClean wired; JIT repro prints 'x'1true. AOT fixture ob_get_contents.phpt exists. Recommend closing as duplicate of #3236/#4877 family unless repro differs.

  4. PurHur commented on Jul 5, 2026

    @PurHur
    PurHur
    on Jul 5, 2026
    OwnerAuthor

    claim: PHP Compiler STD Lib — starting this run

  5. PurHur commented on Jul 5, 2026

    @PurHur
    PurHur
    on Jul 5, 2026
    OwnerAuthor

    claim released: already green on master — JIT repro ob_start/echo/ob_get_contents prints 'x'; capabilities.md shows yes/yes/yes for ob_get_contents/ob_get_length/ob_end_clean with AOT PHPT. Pivoting.

  6. PurHur commented on Jul 6, 2026

    @PurHur
    PurHur
    on Jul 6, 2026
    OwnerAuthor

    claim: PHP Compiler STD Lib — starting this run (JIT/AOT ob_get_contents/ob_get_length/ob_end_clean)

  7. PurHur commented on Jul 6, 2026

    @PurHur
    PurHur
    on Jul 6, 2026
    OwnerAuthor

    WIP handoff (2026-07-06):

    Root cause (AOT): User-script AOT installs EmbedObEchoBridge direct-write(2) echo before ob_start(). Exec-capture ob stack (ObOutputExecCaptureJitHelper) buffers via __phpc_ob_append_bytes, but echo never routes there — hello hits stdout, then ob_get_contents reads an empty/corrupt buffer → segfault.

    Progress this run:

    • Added ObOutputRuntime::ensureReadApiLinked() + extended ObOutputExecCaptureJitHelper with getContents/getLength/endClean/getLevel.
    • Wired JitObGetContents / JitObGetLength / JitObEndClean / JitObGetLevel to lazy-link read API.
    • AOT link fixed (was undefined __phpc_ob_*); ob_end_clean_no_buffer AOT now runs (notice/return-value still wrong: prints null not false).
    • VM + JIT compliance for ob_get_contents.phpt remain green.
    • Registered ob_get_contents / ob_get_length / ob_end_clean in AOT_USER_SCRIPT_REAL_OUTPUT.

    Next step to merge: When read API is linked, replace or bypass user-script direct echo with ObOutputEchoJitEmit::implementAll (append-bytes path), or teach EmbedObEchoBridge to consult active ob depth before write(2). Then fix ob_end_clean AOT bool return + notice emission.

  8. PurHur commented on Jul 7, 2026

    @PurHur
    PurHur
    on Jul 7, 2026
    OwnerAuthor

    claim: PHP Compiler STD Lib — starting this run (continue AOT ob_get_contents echo routing handoff)

  9. PurHur commented on Jul 7, 2026

    @PurHur
    PurHur
    on Jul 7, 2026
    OwnerAuthor

    claim: PHP Runtime → PHP — starting this run.

  10. PurHur commented on Jul 7, 2026

    @PurHur
    PurHur
    on Jul 7, 2026
    OwnerAuthor

    claim follow-up — runtime investigation (#4914)

    Status this run

    JIT path: already green (hello50 via bin/jit.php).

    AOT user-script path: blocked on two layers:

    1. Link: __phpc_ob_get_contents / __phpc_ob_get_length / __phpc_ob_end_clean / __phpc_ob_get_level are declared by ObOutputUserScriptLlvm but only echo bridges are emitted; read/discard ABIs are missing at link time.

    2. Runtime (when stubs added): exec-capture LLVM bridges compile+link but AOT binaries segfault in ob_get_clean/ob_get_contents even on master — value-returning JitNestedHelperCoerce path on ObOutputExecCaptureJitHelper appears broken for user-script AOT. Full ObOutputJitBridge::implementObStack fixes semantics but nested-JIT of ObOutputJitHelper.php fails module verify (STDOUT / __compiler_is_stream_filter_resource) under PHP_COMPILER_AOT_USER_SCRIPT=1.

    Partial progress landed on branch agent/issue-4914-ob-read-api-aot

    Recommended next step

    Emit read/discard ABIs on the same exec-capture static stack (extend ObOutputExecCaptureJitHelper + LLVM bridges in one nested-JIT unit), or add a prelinked helper-runtime unit for ObOutputJitHelper.php and route user-script read APIs through ObOutputJitBridge without inline nested JIT during bin/compile.php.

    Verification target:

    HARNESS_DOCKER_RUN_OPTS='--memory=8g --cpus=2' ./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter ob_get_contents'

  11. PurHur commented on Jul 10, 2026

    @PurHur
    PurHur
    on Jul 10, 2026
    OwnerAuthor

    claim: PHP Compiler STD Lib — starting this run (#4914 ob_get_contents/ob_get_length/ob_end_clean AOT link symbols)

  12. PurHur commented on Jul 10, 2026

    @PurHur
    PurHur
    on Jul 10, 2026
    OwnerAuthor

    Merged via #17653.

    Root cause: User-script AOT used ObOutputExecCaptureLlvm for ob_start/echo capture but never emitted __phpc_ob_get_contents, __phpc_ob_get_length, __phpc_ob_end_clean, or __phpc_ob_get_level — link failed while JIT/VM were green.

    Fix: LLVM read/discard bridges on existing ObStorageGlobals stack + lazy link from JitOb* lowering.

    Verification: vendor/bin/phpunit --filter ob_get_contents OK (3 tests incl. AOT ob_get_contents.phpt); JIT smoke prints hello50.

  13. PurHur
    added a commit that references this issue on Jul 10, 2026

    Stdlib/AOT: link ob_get_contents/get_length/end_clean for user-script (…

    de3eb58
  14. PurHur
    closed this as completedin #17653on Jul 10, 2026
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