DX: debuggable binaries — DWARF line info via LLVM DIBuilder, PHP-level stack traces with file:line on uncaught exceptions, `phpc build --debug`, `--asan`, and a `phpc profile` that maps perf samples back to PHP functions (lib/JIT/AotDebugSymbols.php, lib/JIT/Context.php, lib/AOT/Linker.php)

[PurHur]

Category

Tooling: · developer experience when something goes wrong · child of #36379

Why

When an AOT binary misbehaves today the user gets phpc: fatal signal (segfault) after c:main_before_php or a 672 KB IR dump. There is no line info in the binary (AotDebugSymbols.php exists but emits no DWARF), uncaught exceptions print no PHP trace with file:line under AOT, and profiling shows PHPCompiler_ext_standard_… symbols with no mapping to user code. Every wave-1 diagnosis needed objdump and /proc — that is not a workflow users will follow.

Deliverable

• --debug: emit DICompileUnit/DISubprogram/DILocation for user functions and statements via the bound LLVMDIBuilder* API (in ffi/llvm9.php), keep symbols, no -s; gdb/perf show file.php:line.
• Uncaught exception / fatal under AOT prints the Zend-shaped trace (#0 file(line): fn()), including for exceptions crossing helper units; debug_backtrace() returns file/line/function.
• --asan: link with -fsanitize=address runtime and the runtime's own allocations instrumented (poison on free); used by Stdlib: count, array_key_exists, is_object and VM fixes #19's CI job.
• phpc profile <binary> [args]: runs under perf record, resolves symbols through a generated symbol → PHP function map, prints a flat + callgraph report; documented in docs/performance.md.
• Crash handler: on SIGSEGV/SIGABRT print the PHP-level trace of the current frame stack (frame pointers are kept in debug builds) before exiting 139.

Done when

• gdb on a --debug hello shows hello.php:1; uncaught-exception trace matches Zend on the Stdlib: floatval, boolval, gettype(null) and expanded PHPT specs #5 corpus
• phpc profile output for benchmarks/v2/nbody names the PHP function at the top; documented

[PurHur]

claim: implementer-worker-lane-b — starting this run (lane B tie-break #36394 % 3 == 1; lane overflow: #36143–#36148 closed). First slice: AOT uncaught nested stack matches Zend (e18 is skipped today because the printer hardcodes #0 {main}).

[PurHur]

Merged #36502 — first slice only: AOT nested uncaught traces match Zend (e18 / test/repro/aot_uncaught_nested_trace_36394.php; stderr byte-identical, rc 255).

Still open vs issue Done-when: gdb on --debug hello (file.php:1), phpc profile nbody map, --asan link. Those were not in this PR; file a successor if they remain in scope.