feat: add C++ header-only exporter for embedded/MCU use by SoundMatt · Pull Request #526 · COVESA/vss-tools

SoundMatt · 2026-05-22T21:57:14Z

Summary

Adds vspec export cpp-header (new file src/vss_tools/exporters/cpp_header.py)
Emits a single .hpp with a VssSignal struct and one constexpr aggregate per leaf signal
Allowed-value lists become null-terminated constexpr const char*[] arrays declared immediately above their signal
VssSignal.cpp_type maps VSS datatypes to C++ equivalents (uint8_t, float, const char*, bool, …) using the same type table as datatypes.py
--namespace (default vss) and --include-branches/--no-include-branches CLI flags
No new runtime dependencies; header requires only <cstddef> and <cstdint>

Resolves #513.

Test plan

uv run pytest tests/vspec/test_cpp_header/ passes
vspec export cpp-header -s <spec> -o out.hpp produces valid C++ (compile-checked manually with g++ -std=c++17 -c out.hpp)
Signals with no allowed values emit nullptr for allowed_values
Signals with allowed values emit a named null-terminated array above the aggregate

erikbosch · 2026-05-29T08:23:54Z

@@ -0,0 +1,215 @@
+# Copyright (c) 2024 Contributors to COVESA


New file, change to 2026 unless copied in full from somewhere else

erikbosch · 2026-05-29T08:24:54Z

@@ -0,0 +1,81 @@
+// SPDX-FileCopyrightText: Copyright (c) 2024 Contributors to COVESA


New file, use 2026

By the way - does our license checker complains if this file does not have a license text? If this tool is intended to be used by customers the output does not necessarily needs to be with a MPL license, and copyright is not necessarily only COVESA as it is based on signal definitions that might be proprietary.

I am thinking of removing the copyright/license part here, and if needed adjust the license reviewer so it does not care about this file.

erikbosch · 2026-05-29T08:30:15Z

@JMorceaux - is this what you need?

erikbosch · 2026-05-29T08:32:47Z

Awaiting feedback from Jeremy. before merging the file https://github.com/COVESA/vss-tools/blob/master/docs/vspec.md shall be expanded and reference a file cpp-header.mdthat gives a short overview of this tool. See how other tools are documented

JMorceaux · 2026-06-01T08:01:46Z

Thanks @erikbosch for the ping ! Just came back from vacation, I'll definitely look at at this PR in details because it might indeed be exactly what I need :)

JMorceaux · 2026-06-01T08:03:00Z

+@click.option(
+    "--include-branches/--no-include-branches",
+    default=False,
+    show_default=True,
+    help="Include branch nodes in addition to leaf signals.",
+)


@SoundMatt Thank you for this PR. In the current state, your exporter would export the entire vss specs and put all signals in the .hpp. The VSS specs is starting to be a bit heavy and I fear the .text/.bss is gonna be huge if we export all signals. I think it would be nice if the user could give the tool a list of signals (as an option) to export and only these signals would be exported. This would reduce .text/.bss and better suited for MCU use.

JMorceaux · 2026-06-01T08:15:22Z

+    "sensor",
+    "float",
+    "float",
+    "km",


The advantage of using const char*/string is that it's pretty robust to change but if we want to make an exporter for embedded system, it is best to think about memory footprint.

I think it would be best if an enum was created for unit/type/datatype/cpp_type

Same thing for the min/max value, I don't think a string is appropriate here

Adds `vspec export cpp-header` which emits a single `.hpp` containing a `VssSignal` struct and one `constexpr` instance per leaf signal. Allowed-value lists become null-terminated `constexpr const char*[]` arrays declared immediately above the signal aggregate. The struct includes a `cpp_type` field that maps VSS datatypes to their C++ equivalents (uint8_t, float, const char*, bool, etc.) derived from the existing Datatypes enum. Resolves COVESA#513. Signed-off-by: Matt Jones <47545907+SoundMatt@users.noreply.github.com>

Signed-off-by: Matt Jones <47545907+SoundMatt@users.noreply.github.com>

Adds docs/cpp-header.md covering the exporter's purpose, CLI flags (--namespace, --include-branches), VSS→C++ type mapping table, and a concrete model.vspec → vss.hpp example. Adds a reference link in docs/vspec.md alongside the other exporter docs. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Signed-off-by: Matt Jones <47545907+SoundMatt@users.noreply.github.com>

…or min/max Replace all const char* metadata fields in VssSignal with typed enums: - VssNodeType (sensor/actuator/attribute/branch) - VssDataType (all VSS primitive and array types) - VssCppType (all C++ type mappings) - VssUnit (per-export enum of units actually present; kNone for unset) min_value/max_value change from const char* to double (kNoValue sentinel = std::numeric_limits<double>::quiet_NaN() for unset). Requires <limits>. Also updates copyright year to 2026 in the exporter source and generated header output. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Signed-off-by: Matt Jones <47545907+SoundMatt@users.noreply.github.com>

SoundMatt · 2026-06-15T13:46:15Z

Updated in the latest commit:

Enums for type/datatype/cpp_type/unit — VssNodeType, VssDataType, VssCppType are fixed enums covering all VSS types. VssUnit is a per-export enum containing only the units present in the output (so the emitted enum stays small on a filtered spec). All four replace the previous const char* fields.
double for min/max — min_value/max_value are now double with a kNoValue = std::numeric_limits<double>::quiet_NaN() sentinel for unset values (requires <limits>).
Copyright year — updated to 2026 in both the exporter source and the generated header.

@JMorceaux — on the --signals filter: before I build it, can you describe the expected UX? My current thinking is a repeatable --signal option that accepts dotted paths, e.g.:

vspec export cpp-header --signal Vehicle.Speed --signal Vehicle.Body.Lights.IsBackupOn -s spec/... -o out.hpp

Only the named paths (and their parent branches, if --include-branches is set) would be emitted. Glob patterns welcome too (Vehicle.ADAS.*).

Does that match what you had in mind, or did you want something different (e.g., a file listing paths, prefix-based filtering, etc.)? Happy to implement once we're aligned on scope.

sschleemilch · 2026-07-21T12:25:52Z

+
+namespace vss {
+
+struct VssSignal {


Why not just Signal. Its already in the vss namespace

sschleemilch · 2026-07-21T12:27:10Z

+from vss_tools.tree import VSSNode
+
+_CPP_TYPE_MAP: dict[str, str] = {
+    "uint8": "uint8_t",


should use datatypes.py definitions

sschleemilch · 2026-07-21T12:27:43Z

+}
+
+_NODE_TYPE_ENUM: dict[str, str] = {
+    "sensor": "VssNodeType::kSensor",


Why not just NodeType?

sschleemilch · 2026-07-21T12:27:53Z

+}
+
+_DATATYPE_ENUM: dict[str, str] = {
+    "uint8": "VssDataType::kUint8",


sschleemilch · 2026-07-21T12:28:57Z

+}
+
+_CPP_TYPE_ENUM: dict[str, str] = {
+    "uint8_t": "VssCppType::kUint8T",


Suggested change

"uint8_t": "VssCppType::kUint8T",

"uint8_t": "kUint8T",

sschleemilch · 2026-07-21T12:30:22Z

+    """Convert a VSS unit string to a C++ enum member name prefixed with k."""
+    s = unit
+    s = s.replace("/", "_Per_")
+    s = s.replace("^", "_Pow_")


what vss unit contains those symbols?

sschleemilch · 2026-07-21T12:33:34Z

+    else:
+        allowed_ref = "nullptr"
+
+    lines.append(f"constexpr VssSignal {ident} = {{")


I feel like this should be a real template engine like jinja2

sschleemilch · 2026-07-21T12:34:26Z

+    unit_map = {u: f"VssUnit::{m}" for u, m in seen_units.items()}
+
+    out: list[str] = []
+    out.append("// SPDX-FileCopyrightText: Copyright (c) 2026 Contributors to COVESA")


sschleemilch · 2026-07-21T12:34:54Z

        "yaml": "vss_tools.exporters.yaml:cli",
        "tree": "vss_tools.exporters.tree:cli",
        "samm": "vss_tools.exporters.samm:cli",
+        "cpp-header": "vss_tools.exporters.cpp_header:cli",


how about hpp?

erikbosch reviewed May 29, 2026

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erikbosch mentioned this pull request May 29, 2026

C++ exporter (and why not Rust later) #513

Open

JMorceaux reviewed Jun 1, 2026

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SoundMatt added 4 commits June 15, 2026 06:40

fix: resolve ruff lint/format violations in cpp_header exporter

37d3f80

Signed-off-by: Matt Jones <47545907+SoundMatt@users.noreply.github.com>

SoundMatt force-pushed the feat/cpph-exporter branch from 75c7b8e to 274e05f Compare June 15, 2026 13:46

sschleemilch reviewed Jul 21, 2026

View reviewed changes

		@@ -0,0 +1,215 @@
		# Copyright (c) 2024 Contributors to COVESA

		@@ -0,0 +1,81 @@
		// SPDX-FileCopyrightText: Copyright (c) 2024 Contributors to COVESA

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SoundMatt commented May 22, 2026

Summary

Test plan

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erikbosch commented May 29, 2026

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SoundMatt commented Jun 15, 2026

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JMorceaux Jun 1, 2026 •

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