[fornwall]

The lib-vt Zig compilation unit was emitted as one text and data section, so linker garbage collection retained the entire C API.

Enable per-function and per-data sections for static artifacts. Force LLVM code generation because the self-hosted x86 backend accepts these flags without splitting the unit, while leaving shared artifacts unchanged.

Ghostling size impact

Ghostling PR #17 updates Ghostling for the current lib-vt API and Zig 0.16. Its branch links the shared ghostty-vt target, while current Ghostty provides a ghostty-vt-static imported target with GHOSTTY_STATIC and the platform link dependencies. Changing that one target makes Ghostling build successfully against the static lib-vt.

I built the PR #17 branch twice against adjacent Ghostty commits, changing only whether this patch was applied: f64f4ac before and f848494 after.

Static Ghostling	Stripped bytes	Linked ghostty_* definitions
Before	3,500,600	189
With this PR	3,115,576	64
Savings	385,024 (376 KiB, 11.00%)	125

For context, the stripped shared build was 1,433,088 bytes for ghostling plus 2,006,064 bytes for libghostty-vt.so, or 3,439,152 bytes together. The patched static executable was 323,576 bytes (9.41%) smaller than that two-file payload.

Seeing similar savings in another internal program embedding libghostty.

Measurement environment

• Linux 7.0.0-29-generic x86_64
• Ghostling PR #17 at 89da5be, Raylib 5.5, and current Ghostty (f64f4ac versus this PR's f848494)
• Zig 0.16.0 from /home/linuxbrew/.linuxbrew/bin/zig, GCC 15.2.0, GNU ld/strip 2.46, CMake 4.2.3, and Ninja 1.13.2
• X11 development libraries from Linuxbrew, including libXinerama 1.1.6

Both static variants changed Ghostling's link target to ghostty-vt-static and used:

cmake -B build -G Ninja \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_EXE_LINKER_FLAGS_RELEASE=-Wl,--gc-sections \
  -DFETCHCONTENT_SOURCE_DIR_GHOSTTY=<ghostty-worktree> \
  -DFETCHCONTENT_SOURCE_DIR_RAYLIB=<raylib-5.5-source> \
  -DCMAKE_INCLUDE_PATH=/home/linuxbrew/.linuxbrew/include \
  -DCMAKE_LIBRARY_PATH=/home/linuxbrew/.linuxbrew/lib
cmake --build build
strip --strip-all ghostling

This compiles Ghostling and Raylib with -O3 -DNDEBUG. Ghostty's CMake wrapper maps the Release configuration to Zig ReleaseFast and invokes zig build -Demit-lib-vt -Doptimize=ReleaseFast.

Verification

• A native Debug build emits 6,519 text sections in the Zig object instead of one; a ReleaseFast build emits 1,150.
• A minimal embedder referencing one C API function retains one ghostty_* symbol instead of all 189.
• The stripped ReleaseFast minimal test executable is 82 KiB with section GC versus 2.1 MiB without it.
• Native Linux, cross-compiled Windows, and cross-compiled macOS builds pass. COFF emits .text$... and .rdata$... sections; Mach-O emits MH_SUBSECTIONS_VIA_SYMBOLS.

Tradeoffs

• The ReleaseFast static archive grew from 18,975,324 to 19,497,556 bytes (522,232 bytes, 2.75%) because it contains more section metadata. Consumers only realize the size reduction when their linker enables section garbage collection.
• More input sections can increase linker work and memory use. This was not benchmarked.
• Forcing LLVM is necessary for the flags to take effect on the self-hosted x86 backend. It means static lib-vt builds require an LLVM-enabled Zig compiler and may use more compile time or memory, especially for Debug builds. Shared lib-vt builds are unchanged.

LLVM references

• Clang -ffunction-sections
• Clang -fdata-sections
• LLVM TargetMachine section controls
• LLD section-GC retention guidance