Language: __COMPILER_HALT_OFFSET__ magic constant (phase 2 of #3479, zend_compile.c)

[PurHur]

Category

language

Problem

__halt_compiler() lowering landed (#3479), but the companion magic constant __COMPILER_HALT_OFFSET__ is still undefined at runtime. PHAR stubs and codegen tools rely on the byte offset of the first halt instruction.

Verified 2026-06-04: halt stops execution, but reading the constant fatals.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_halt_compiler() sets ZEND_COMPILE_HALT_OFFSET
• php/php-src Zend/zend_language_scanner.l — T_COMPILER_HALT_OFFSET
• php/php-src ext/phar/phar.c — stub layout uses offset

Repro

<?php
echo __COMPILER_HALT_OFFSET__, "\n";
__halt_compiler();
TRAILING

./script/docker-exec.sh bash -lc 'php repro.php'          # prints int offset (e.g. 89)
./script/docker-exec.sh bash -lc 'php bin/vm.php repro.php' # Error: Undefined constant "__COMPILER_HALT_OFFSET__"

Engine	Expected
Zend	int(N) — byte offset of halt in compiled file
This compiler	same int on VM and AOT

Scope (this repo)

Layer	Path
Compiler	lib/Compiler.php — record halt byte offset per compilation unit (extend existing #3479 trailing-bytes fields)
php-cfg / parse	expose offset from Stmt\HaltCompiler site
VM	lower as script magic constant like __LINE__ / __FILE__
JIT/AOT	constexpr per module; no host \__COMPILER_HALT_OFFSET__
Tests	test/compliance/cases/language/compiler_halt_offset.phpt

Done when

• Repro prints the same integer offset as Zend for the same source file
• Constant available before and after __halt_compiler() call (Zend allows both)
• ./script/ci-fast.sh --filter compiler_halt_offset green
• Language: __halt_compiler() — stop parsing and preserve trailing bytes (Zend zend_compile.c parity) #3479 checklist references this for phase 2 close-out

Related

• Language: __halt_compiler() — stop parsing and preserve trailing bytes (Zend zend_compile.c parity) #3479 — __halt_compiler() parse stop + trailing bytes
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 — PHAR / self-host tooling may depend on offset

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

Merged via #5482

Verification

• php bin/vm.php test/repro-maintainer/compiler_halt_offset.php → 61 (matches Zend)
• PHPUnit: HaltCompilerVMTest::testCompilerHaltOffsetMatchesTrailingBoundary, compiler_halt_offset.phpt — OK

Offset is the byte position where trailing data after __halt_compiler(); begins (same as Zend strlen(source) - strlen(remaining)).