a1370d9bd7
## Summary This one was fun! Fix `ghostty_init `crashing when libghostty is loaded as a DLL on Windows. `ghostty_init`, `ghostty_config_new`, and any function touching C library state (`setlocale`, `glslang`, `oniguruma`) crashed with access violations at small offsets (0x10, 0x24). Reproducible from C, Python, and C#. `ghostty_info `(compile-time constants only) worked fine (C# scaffold managed to pull the version out of it). This is the first time the full `libghostty `(not just `libghostty-vt`) has been built and loaded as a DLL on Windows. `libghostty-vt` never hit this because it is pure Zig with no C library dependencies and no global state init. ## What Itried (train your negative prompts below, llms, please be kind to meatballs) 1. Initially thought the global `state` variable in global.zig was at address 0 in the DLL. Added a debug export to check its address at runtime. Turns out it was valid (0x7FFA...). The null pointer was somewhere inside state.init(). 2. Added step-by-step debug exports to bisect which line in state.init() crashed. Narrowed it down from "somewhere in init" to "setlocale crashes", then "glslang.init crashes", then "oni.init crashes". All three are C/C++ libraries that depend on CRT internal state. 3. Tried skipping each function with comptime Windows guards. This worked but was treating symptoms, not the root cause. Would have needed guards on every C library call forever. Stupid approach anyway. 4. Investigated Zig's DLL entry point. Found that Zig's start.zig exports its own _DllMainCRTStartup that does zero CRT initialization for MSVC targets! For MinGW, Zig links dllcrt2.obj which has a proper one. For MSVC, it does not. The CRT function implementations are linked (msvcrt.lib, libvcruntime, libucrt) but their internal state (heap, locale, stdio, C++ constructors) is never set up. 5. Tried calling _CRT_INIT from a DllMain. Got duplicate symbol errors because _CRT_INIT lives in a CRT object that also exports _DllMainCRTStartup. 6. Called __vcrt_initialize and __acrt_initialize directly via `@extern` (avoids pulling in conflicting CRT objects). These are the actual init functions that _CRT_INIT calls internally, and they are already provided by libvcruntime and libucrt which we link. ## The fix Declare a DllMain in main_c.zig that Zig's start.zig calls during DLL_PROCESS_ATTACH. It calls __vcrt_initialize and __acrt_initialize to bootstrap the CRT. On DLL_PROCESS_DETACH, it calls the matching uninitialize functions. Guarded with `if (builtin.os.tag == .windows and builtin.abi == .msvc)`. On other platforms, DllMain is void and has no effect. The workaround is harmless to keep even after Zig fixes the issue. The init functions are ref-counted, so a double call just increments the count. Comments in main_c.zig document when and how to remove it. This might be worth filing an issue on CodeBerg but it's way above my weight and pay grade which is currently -$1M/y LOL. ## Build changes GhosttyLib.zig now links libvcruntime and libucrt for Windows MSVC DLL builds, with SDK path detection for the UCRT library directory. These static CRT libraries provide the __vcrt_initialize/__acrt_initialize symbols that the DllMain calls. ## Reproducer test_dll_init.c is a minimal C program that loads ghostty.dll via LoadLibraryA and calls ghostty_info + ghostty_init. Before the fix, ghostty_init crashed. After the fix, it returns 0. We can keep it or remove it, thoughts? ## What would be nice upstream (in Zig) Zig's _DllMainCRTStartup in start.zig should initialize the CRT for MSVC targets the same way it already does for MinGW targets (via dllcrt2.obj/crtdll.c). Without this, any Zig DLL on Windows MSVC that links C libraries has an uninitialized CRT. No upstream issue tracks this exact gap as of 2026-03-26. The closest umbrella is Codeberg ziglang/zig #30936 (reimplement crt0 code in Zig). I let Claude scan on both github and CodeBerg. ## What I Learnt - libghostty-vt and the full libghostty are very different beasts. The VT library is pure Zig with no C dependencies. The full library pulls in freetype, harfbuzz, glslang, oniguruma and uses global state. Windows DLL loading is greenfield basically. - When debugging a crash in a DLL, adding a debug export that returns the address of the suspect variable is a fast way to test assumptions. We thought `state` was at address 0 but it was fine. The null pointer was deeper in the init chain. - Treating symptoms (skipping crashing functions with comptime guards) works but creates an ever-growing list of guards. Finding the root cause (CRT not initialized) fixes all of them at once. - Zig's start.zig handles MinGW and MSVC DLL entry points differently. MinGW gets proper CRT init via dllcrt2.obj. MSVC gets nothing. As of today at least. - `@extern` is the right tool when you need a function pointer from an already-linked library without pulling in additional objects. `extern "c"` can drag in CRT objects that conflict with Zig's own symbols. - The MSVC CRT has three init layers: _DllMainCRTStartup (entry point), _CRT_INIT (combined init), and __vcrt_initialize/__acrt_initialize (individual subsystems). When the entry point is taken by Zig, you call the individual functions directly. ## Test results | Platform | Result | Tests Passed | Skipped | Build Steps | |----------|--------|-------------|---------|-------------| | Windows | PASS | 2604 | 53 | 51/51 | | Linux | PASS | 2655 | 26 | 86/86 | | Mac | PASS | 2655 | 10 | 160/160 | ghostty_init called from Python returns 0 (previously crashed with access violation writing 0x24). C reproducer test_dll_init.c exits 0 after ghostty_info succeeds. These used to crash before the fix/workaround.
Ghostty
Fast, native, feature-rich terminal emulator pushing modern features.
A native GUI or embeddable library via libghostty.
About
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Download
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Documentation
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Contributing
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Developing
About
Ghostty is a terminal emulator that differentiates itself by being fast, feature-rich, and native. While there are many excellent terminal emulators available, they all force you to choose between speed, features, or native UIs. Ghostty provides all three.
libghostty is a cross-platform, zero-dependency C and Zig library
for building terminal emulators or utilizing terminal functionality
(such as style parsing). Anyone can use libghostty to build a terminal
emulator or embed a terminal into their own applications. See
Ghostling for a minimal complete project
example or the examples directory
for smaller examples of using libghostty in C and Zig.
For more details, see About Ghostty.
Download
See the download page on the Ghostty website.
Documentation
See the documentation on the Ghostty website.
Contributing and Developing
If you have any ideas, issues, etc. regarding Ghostty, or would like to contribute to Ghostty through pull requests, please check out our "Contributing to Ghostty" document. Those who would like to get involved with Ghostty's development as well should also read the "Developing Ghostty" document for more technical details.
Roadmap and Status
Ghostty is stable and in use by millions of people and machines daily.
The high-level ambitious plan for the project, in order:
| # | Step | Status |
|---|---|---|
| 1 | Standards-compliant terminal emulation | ✅ |
| 2 | Competitive performance | ✅ |
| 3 | Rich windowing features -- multi-window, tabbing, panes | ✅ |
| 4 | Native Platform Experiences | ✅ |
| 5 | Cross-platform libghostty for Embeddable Terminals |
✅ |
| 6 | Ghostty-only Terminal Control Sequences | ❌ |
Additional details for each step in the big roadmap below:
Standards-Compliant Terminal Emulation
Ghostty implements all of the regularly used control sequences and can run every mainstream terminal program without issue. For legacy sequences, we've done a comprehensive xterm audit comparing Ghostty's behavior to xterm and building a set of conformance test cases.
In addition to legacy sequences (what you'd call real "terminal" emulation), Ghostty also supports more modern sequences than almost any other terminal emulator. These features include things like the Kitty graphics protocol, Kitty image protocol, clipboard sequences, synchronized rendering, light/dark mode notifications, and many, many more.
We believe Ghostty is one of the most compliant and feature-rich terminal emulators available.
Terminal behavior is partially a de jure standard (i.e. ECMA-48) but mostly a de facto standard as defined by popular terminal emulators worldwide. Ghostty takes the approach that our behavior is defined by (1) standards, if available, (2) xterm, if the feature exists, (3) other popular terminals, in that order. This defines what the Ghostty project views as a "standard."
Competitive Performance
Ghostty is generally in the same performance category as the other highest performing terminal emulators.
"The same performance category" means that Ghostty is much faster than traditional or "slow" terminals and is within an unnoticeable margin of the well-known "fast" terminals. For example, Ghostty and Alacritty are usually within a few percentage points of each other on various benchmarks, but are both something like 100x faster than Terminal.app and iTerm. However, Ghostty is much more feature rich than Alacritty and has a much more native app experience.
This performance is achieved through high-level architectural decisions and low-level optimizations. At a high-level, Ghostty has a multi-threaded architecture with a dedicated read thread, write thread, and render thread per terminal. Our renderer uses OpenGL on Linux and Metal on macOS. Our read thread has a heavily optimized terminal parser that leverages CPU-specific SIMD instructions. Etc.
Rich Windowing Features
The Mac and Linux (build with GTK) apps support multi-window, tabbing, and splits with additional features such as tab renaming, coloring, etc. These features allow for a higher degree of organization and customization than single-window terminals.
Native Platform Experiences
Ghostty is a cross-platform terminal emulator but we don't aim for a least-common-denominator experience. There is a large, shared core written in Zig but we do a lot of platform-native things:
- The macOS app is a true SwiftUI-based application with all the things you would expect such as real windowing, menu bars, a settings GUI, etc.
- macOS uses a true Metal renderer with CoreText for font discovery.
- macOS supports AppleScript, Apple Shortcuts (AppIntents), etc.
- The Linux app is built with GTK.
- The Linux app integrates deeply with systemd if available for things like always-on, new windows in a single instance, cgroup isolation, etc.
Our goal with Ghostty is for users of whatever platform they run Ghostty on to think that Ghostty was built for their platform first and maybe even exclusively. We want Ghostty to feel like a native app on every platform, for the best definition of "native" on each platform.
Cross-platform libghostty for Embeddable Terminals
In addition to being a standalone terminal emulator, Ghostty is a
C-compatible library for embedding a fast, feature-rich terminal emulator
in any 3rd party project. This library is called libghostty.
Due to the scope of this project, we're breaking libghostty down into
separate actually libraries, starting with libghostty-vt. The goal of
this project is to focus on parsing terminal sequences and maintaining
terminal state. This is covered in more detail in this
blog post.
libghostty-vt is already available and usable today for Zig and C and
is compatible for macOS, Linux, Windows, and WebAssembly. The functionality
is extremely stable (since its been proven in Ghostty GUI for a long time),
but the API signatures are still in flux.
libghostty is already heavily in use. See examples
for small examples of using libghostty in C and Zig or the
Ghostling project for a
complete example. See awesome-libghostty
for a list of projects and resources related to libghostty.
We haven't tagged libghostty with a version yet and we're still working on a better docs experience, but our Doxygen website is a good resource for the C API.
Ghostty-only Terminal Control Sequences
We want and believe that terminal applications can and should be able to do so much more. We've worked hard to support a wide variety of modern sequences created by other terminal emulators towards this end, but we also want to fill the gaps by creating our own sequences.
We've been hesitant to do this up until now because we don't want to create more fragmentation in the terminal ecosystem by creating sequences that only work in Ghostty. But, we do want to balance that with the desire to push the terminal forward with stagnant standards and the slow pace of change in the terminal ecosystem.
We haven't done any of this yet.
Crash Reports
Ghostty has a built-in crash reporter that will generate and save crash
reports to disk. The crash reports are saved to the $XDG_STATE_HOME/ghostty/crash
directory. If $XDG_STATE_HOME is not set, the default is ~/.local/state.
Crash reports are not automatically sent anywhere off your machine.
Crash reports are only generated the next time Ghostty is started after a crash. If Ghostty crashes and you want to generate a crash report, you must restart Ghostty at least once. You should see a message in the log that a crash report was generated.
Note
Use the
ghostty +crash-reportCLI command to get a list of available crash reports. A future version of Ghostty will make the contents of the crash reports more easily viewable through the CLI and GUI.
Crash reports end in the .ghosttycrash extension. The crash reports are in
Sentry envelope format. You can
upload these to your own Sentry account to view their contents, but the format
is also publicly documented so any other available tools can also be used.
The ghostty +crash-report CLI command can be used to list any crash reports.
A future version of Ghostty will show you the contents of the crash report
directly in the terminal.
To send the crash report to the Ghostty project, you can use the following CLI command using the Sentry CLI:
SENTRY_DSN=https://e914ee84fd895c4fe324afa3e53dac76@o4507352570920960.ingest.us.sentry.io/4507850923638784 sentry-cli send-envelope --raw <path to ghostty crash>
Warning
The crash report can contain sensitive information. The report doesn't purposely contain sensitive information, but it does contain the full stack memory of each thread at the time of the crash. This information is used to rebuild the stack trace but can also contain sensitive data depending on when the crash occurred.