Regression: system()/passthru() child stdout not captured in active output buffer (ext/standard/exec.c)

[PurHur]

Category

stdlib · php-src-strict · regression · refs #1492

Problem

When an output buffer is active (ob_start()), Zend system() and passthru() echo child process stdout into that buffer and return the last line (system() only). This compiler returns the last line for system() but leaves the active buffer empty; passthru() buffer is also empty.

Verified 2026-06-28 — repro prints system_ob_ok=1 / passthru_ob_ok=1 on Zend vs 0 on VM.

php-src reference

• php/php-src ext/standard/exec.c — PHP_FUNCTION(system), PHP_FUNCTION(passthru)

Repro

test/repro/maintainer_gap_system_passthru_ob.php

php test/repro/maintainer_gap_system_passthru_ob.php
php bin/vm.php test/repro/maintainer_gap_system_passthru_ob.php

Implementation hints (PHP-in-PHP)

• ext/standard/system.php / passthru.php (or shared exec helper): route captured child stdout through VM output layer so active OB handlers receive it
• Related to Stdlib: system()/passthru() bypass active output buffer — ob_get_clean() empty (ext/standard/exec.c) #10492 (system()/passthru() bypass OB) — ensure fix covers buffered capture, not only default SAPI stdout
• No new C runtime branches; use existing VM output/OB stack

Done when

• Repro: system_ob_ok=1 and passthru_ob_ok=1 on VM
• No regression for unbuffered CLI stdout
• Targeted PHPUnit/compliance guard

Related

• Stdlib: system()/passthru() bypass active output buffer — ob_get_clean() empty (ext/standard/exec.c) #10492 OB bypass · Regression: proc_get_status() reports running=false before child reaped (ext/standard/exec.c) #13079 proc_get_status · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: PHP Compiler STD Lib — batch (issues #13251, #13079)

[PurHur]

Merged in #13258.

Verification: repro test/repro/maintainer_gap_system_passthru_ob.php prints system_ob_ok=1 / passthru_ob_ok=1 on VM; compliance VM+JIT green in Docker. JIT path uses __phpc_ob_echo_* via ObOutputRuntime; VM uses OutputBuffer::append().

[PurHur]

claim: PHP Compiler STD Lib — starting this run (AOT system/passthru_ob segfault exit 139, VM green)

[PurHur]

Merged via #18830

Root cause: JIT assignment coerced Internal builtin __value__* returns (ob_get_clean, system) into native bool/long slots when CFG typed the destination as TYPE_NATIVE_BOOL/TYPE_NATIVE_LONG, overwriting the real string|false box after the ABI wrote it. Secondary fix: broken LLVM CFG in JitExec::runWithStdout for system() last-line return.

Verification:

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_system_passthru_ob.php'
# system_ob_ok=1 passthru_ob_ok=1

./script/docker-exec.sh -- bash -lc 'vendor/bin/phpunit test/aot/AotTest.php --filter system_passthru'
# OK (1 test, 5 assertions)