fix(debug): disable .debug_names to fix GDB warning with multi-CU binaries by ghaith · Pull Request #1675 · PLC-lang/rusty

ghaith · 2026-04-15T12:12:06Z

Summary

Adds a C++ wrapper in plc_llvm that calls DIBuilder::createCompileUnit with NameTableKind::None, since the LLVM C API doesn't expose
this parameter
Disables .debug_names emission by default when compiling with -g (DWARF 5), matching clang's default behavior
Adds --gpubnames CLI flag to opt back into .debug_names emission

Context

When compiling multiple ST files with DWARF 5 debug info, each compilation unit generates its own .debug_names accelerator table. lld
concatenates these into a single ELF section, but GDB cannot parse concatenated tables and warns:
warning: Section .debug_names length X does not match section length Y, ignoring .debug_names.

Neither GCC nor clang emit .debug_names by default — clang explicitly sets nameTableKind: None on its DICompileUnit. The LLVM C API (LLVMDIBuilderCreateCompileUnit) does not expose the NameTableKind parameter, so we bypass it with a C++ wrapper that calls the C++ DIBuilder::createCompileUnit directly.

…control The LLVM C API (LLVMDIBuilderCreateCompileUnit) does not expose the NameTableKind parameter, which controls .debug_names accelerator table emission. This adds a C++ wrapper that calls DIBuilder::createCompileUnit directly, allowing us to set NameTableKind::None (matching clang's default) or NameTableKind::Default for opt-in .debug_names emission. The Rust side exposes a safe `create_debug_info()` function that hides all raw pointer handling and transmutes behind a friendly inkwell-typed API.

…ility When compiling multiple ST files with DWARF 5 debug info, each compilation unit gets its own .debug_names table. The linker (lld) concatenates them, but GDB cannot parse concatenated tables and warns: "Section .debug_names length X does not match section length Y" This matches clang's default behavior of setting nameTableKind: None on DICompileUnit. A new --gpubnames CLI flag allows opting back into .debug_names emission when needed (e.g. for lldb-only workflows).

All debug test snapshots now include nameTableKind: None in the DICompileUnit metadata, reflecting the new default behavior.

github-actions · 2026-04-15T12:18:15Z

Build Artifacts

🐧 Linux

Artifact	Link	Size
`deb-x86_64`	Download	38.6 MB
`schema`	Download	0.0 MB
`stdlib`	Download	33.0 MB
`plc-x86_64`	Download	43.6 MB
`deb-aarch64`	Download	30.9 MB
`plc-aarch64`	Download	43.5 MB

From workflow run

🪟 Windows

Artifact	Link	Size
`stdlib.lib`	Download	4.3 MB
`stdlib.dll`	Download	0.1 MB
`plc.exe`	Download	38.4 MB

From workflow run

Copilot

Pull request overview

This PR changes how DWARF compile units are created so .debug_names (DWARF v5 accelerator table) is disabled by default to avoid GDB warnings when linking multi-compilation-unit binaries, while adding a CLI opt-in to re-enable it.

Changes:

Add a plc_llvm C++/FFI wrapper around llvm::DIBuilder::createCompileUnit to control DICompileUnit::DebugNameTableKind.
Thread a new generate_pubnames option from plc_driver CLI (--gpubnames) through codegen into debug info creation.
Update debug-info-related snapshot expectations to include nameTableKind: None.

Reviewed changes

Copilot reviewed 46 out of 46 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
compiler/plc_driver/src/cli.rs	Adds `--gpubnames` flag to opt into `.debug_names` emission.
compiler/plc_driver/src/lib.rs	Adds `generate_pubnames` to `CompileOptions` with default `false`.
compiler/plc_driver/src/pipelines.rs	Propagates CLI flag into `CompileOptions` and into `CodeGen::new`.
compiler/plc_llvm/src/cpp/llvm_wrapper.cpp	Implements C++ wrapper `createCompileUnit` selecting `DebugNameTableKind::{None,Default}`.
compiler/plc_llvm/src/lib.rs	Adds `create_debug_info` API that calls the C++ wrapper and returns inkwell debug builder/CU wrappers.
src/codegen.rs	Extends `CodeGen::new` to accept and pass through `generate_pubnames`.
src/codegen/debug.rs	Switches to `plc_llvm::create_debug_info(...)` and forwards `generate_pubnames`.
src/test_utils.rs	Updates test helper `CodeGen::new` call sites for the new parameter.
compiler/plc_driver/src/tests/snapshots/plc_driver__tests__multi_files__multiple_files_with_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
compiler/plc_driver/src/tests/snapshots/plc_driver__tests__multi_files__multiple_files_in_different_locations_with_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
tests/integration/snapshots/tests__integration__cfc__ir__actions_debug.snap	Snapshot update to expect `nameTableKind: None`.
tests/integration/snapshots/tests__integration__cfc__ir__conditional_return_debug.snap	Snapshot update to expect `nameTableKind: None`.
tests/integration/snapshots/tests__integration__cfc__ir__jump_debug.snap	Snapshot update to expect `nameTableKind: None`.
tests/integration/snapshots/tests__integration__cfc__ir__sink_source_debug.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/oop_tests/debug_tests.rs	Updates embedded IR expectations for `nameTableKind: None`.
src/codegen/tests/debug_tests.rs	Updates embedded IR expectations for `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__dwarf_version_override.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_alias_type.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_array_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_byteseq_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_float_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_int_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_nested_struct_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_pointer_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_string_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/snapshots/rusty__codegen__tests__debug_tests__global_var_struct_added_to_debug_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__aggregate_return_value_variable_in_function.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__array_size_correctly_set_in_dwarf_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__assignment_statement_have_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__case_conditions_location_marked.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__exit_statement_have_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__external_impl_is_not_added_as_external_subroutine.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__for_conditions_location_marked.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__function_calls_have_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__function_calls_in_expressions_have_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__if_conditions_location_marked.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__implementation_added_as_subroutine.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__nested_function_calls_get_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__non_callable_expressions_have_no_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__non_function_pous_have_struct_as_param.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__repeat_conditions_location_marked.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__return_statement_have_location.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__string_size_correctly_set_in_dwarf_info.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__var_and_vartemp_variables_in_pous_added_as_local.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__var_in_out_inout_in_function_added_as_params.snap	Snapshot update to expect `nameTableKind: None`.
src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__while_conditions_location_marked.snap	Snapshot update to expect `nameTableKind: None`.

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Copilot · 2026-04-16T06:59:54Z

+                let (debug_info, compile_unit) = plc_llvm::create_debug_info(
+                    module,
                    true,
                    inkwell::debug_info::DWARFSourceLanguage::C, //TODO: Own lang
                    filename,
                    root.to_str().unwrap_or_default(),
                    "RuSTy Structured text Compiler",
                    optimization.is_optimized(),
-                    "",
                    0,
-                    "",
                    debug_level.into(),
-                    0,
-                    false,
-                    false,
-                    "",
-                    "",
+                    generate_pubnames,
                );


New behavior is gated on generate_pubnames, but the updated snapshots only cover the default (false) path. Add a test (or a snapshot variant) that sets generate_pubnames = true / passes --gpubnames and asserts the compile unit uses the non-None nameTableKind (i.e., .debug_names is emitted) so this opt-in path can’t regress silently.

Copilot · 2026-04-16T06:59:54Z

+            assert!(size_of::<DebugInfoBuilder>() == size_of::<usize>() + size_of::<PhantomData<&()>>());
+            assert!(
+                size_of::<DICompileUnit>()
+                    == size_of::<DIFile>() + size_of::<usize>() + size_of::<PhantomData<&()>>()
+            );


The compile-time layout verification block won’t compile as written: size_of isn’t in scope and the generic inkwell types require an explicit lifetime parameter (e.g., DebugInfoBuilder<'_>, DICompileUnit<'_>, DIFile<'_>). Use std::mem::size_of::<...>() with <'_> (or import size_of) so this crate builds.

Suggested change

assert!(size_of::<DebugInfoBuilder>() == size_of::<usize>() + size_of::<PhantomData<&()>>());

assert!(

size_of::<DICompileUnit>()

== size_of::<DIFile>() + size_of::<usize>() + size_of::<PhantomData<&()>>()

);

assert!(

std::mem::size_of::<DebugInfoBuilder<'_>>()

== std::mem::size_of::<usize>() + std::mem::size_of::<PhantomData<&()>>()

);

assert!(

std::mem::size_of::<DICompileUnit<'_>>()

== std::mem::size_of::<DIFile<'_>>()

+ std::mem::size_of::<usize>()

+ std::mem::size_of::<PhantomData<&()>>()

);

Copilot · 2026-04-16T06:59:55Z

+        let debug_info: DebugInfoBuilder<'ctx> = std::mem::transmute(builder_ref);
+        let compile_unit: DICompileUnit<'ctx> =
+            std::mem::transmute((file_ref, cu_ref, PhantomData::<&'ctx ()>));
+


std::mem::transmute is being used to construct DebugInfoBuilder/DICompileUnit from raw pointers/tuples. This is only sound if those inkwell wrapper types have a guaranteed representation compatible with the transmuted values; size checks + debug asserts don’t make the layout guarantee in release builds. Prefer an API that constructs these wrappers from raw LLVM pointers (or add such a constructor in a small local wrapper layer) to avoid relying on inkwell’s private layout.

ghaith added 4 commits April 15, 2026 14:07

test: update debug info snapshots for nameTableKind: None

14bb2e2

All debug test snapshots now include nameTableKind: None in the DICompileUnit metadata, reflecting the new default behavior.

Merge branch 'master' into debug_names_length

ecc7b44

ghaith marked this pull request as ready for review April 16, 2026 06:53

ghaith requested a review from Copilot April 16, 2026 06:53

Copilot started reviewing on behalf of ghaith April 16, 2026 06:54 View session

Copilot AI reviewed Apr 16, 2026

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ghaith marked this pull request as draft April 22, 2026 07:10

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fix(debug): disable .debug_names to fix GDB warning with multi-CU binaries#1675

fix(debug): disable .debug_names to fix GDB warning with multi-CU binaries#1675
ghaith wants to merge 4 commits into
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debug_names_length

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ghaith commented Apr 15, 2026

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