@retrovm/nobj

Generate native linkable object files — COFF, Mach-O and ELF64 — containing exported read-only data symbols, directly from TypeScript/Bun.

No native dependencies. No spawn. No temp files. Just a Buffer out.

The problem

Embedding binary assets in a C/C++ project is usually done as a static array:

// generated by xxd or similar
static const unsigned char font_data[] = {
    0x00, 0x01, 0x02, 0x03, /* ... 512 KB of this ... */
};

This works, but it doesn't scale. Clang has to parse, lex and codegen every single byte as a numeric literal. A 1 MB asset becomes a translation unit with a million tokens — compilation slows to a crawl and RAM usage spikes. With several large assets the build becomes the bottleneck.

The right fix is to put the data in a proper object file and let the linker handle placement. This library generates that object file in pure TypeScript, with no external tools required.

Install

bun add @retrovm/nobj

Usage

import { encodeSymbols } from '@retrovm/nobj'

const buf = encodeSymbols([
  { name: 'font_data',   obj: Buffer.from(await Bun.file('font.bin').bytes()) },
  { name: 'shader_src',  obj: '#version 330\nvoid main() {}' },
  { name: 'sample_rate', obj: 44100.0 },
])

await Bun.write('assets.o', buf)

Link normally:

# Any Os
clang main.c assets.o -o app

Reference from C with no runtime overhead:

extern const unsigned char font_data[];
extern const char          shader_src[];
extern const double        sample_rate;

API

encodeObject(name, obj, arch?, platform?)

Encodes a single symbol.

const buf = encodeObject('palette', paletteBuffer)

encodeSymbols(symbols[], arch?, platform?)

Encodes multiple symbols into one object file. Preferred for production — one file, one link step.

const buf = encodeSymbols([
  { name: 'icon_png',  obj: iconBuffer },
  { name: 'main_glsl', obj: shaderSource },
])

Symbol values

| TypeScript type | C declaration | Notes | |-----------------|--------------------------|----------------------------------------| | Uint8Array | const uint8_t[] | Raw bytes, no transformation | | string | const char[] | ASCII, null-terminated (except macOS) | | number | const double | IEEE 754, 8 bytes |

Cross-compilation

By default both platform and architecture are inferred from the running process. Override to cross-compile:

encodeSymbols(symbols, 'arm64', 'linux')   // Linux/arm64
encodeSymbols(symbols, 'x64',   'win32')   // Windows/x64
encodeSymbols(symbols, 'arm64', 'macos')   // macOS/arm64

| TargetPlatform | Format | Section | |------------------|--------|-----------| | 'win32' | COFF | .rdata | | 'macos' | Mach-O | __const | | 'linux' | ELF64 | .rodata |

| TargetArch | COFF machine | Mach-O cputype | |--------------|--------------|----------------| | 'x64' | 0x8664 | 0x1000007 | | 'arm64' | 0xAA64 | 0x100000C |

Format notes

The generated files are minimal but correct — accepted by clang, lld and ld without warnings, and readable by llvm-readobj, dumpbin and objdump.

• COFF — includes a .drectve section with /EXPORT directives and @feat.00 to satisfy MSVC/clang-cl safe-SEH requirements.
• Mach-O — emits LC_BUILD_VERSION targeting macOS 10.9 so modern ld accepts the file without deprecation warnings. Symbol values are section-relative offsets, as required for relocatable objects.
• ELF64 — uses a single .strtab as both sh_strtab and symbol string table. Includes an empty .note.GNU-stack to mark the stack as non-executable.

License

Copyright (c) 2026 Juan Carlos González Amestoy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.