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The name of the game here is to avoid CreateProcessW calls at all costs, and only ever try calling it when we have a real candidate for execution. Secondarily, we want to minimize the number of syscalls used when checking for each PATHEXT-appended version of the app name. An overview of the technique used: - Open the search directory for iteration (either cwd or a path from PATH) - Use NtQueryDirectoryFile with a wildcard filename of `<app name>*` to check if anything that could possibly match either the unappended version of the app name or any of the versions with a PATHEXT value appended exists. - If the wildcard NtQueryDirectoryFile call found nothing, we can exit early without needing to use PATHEXT at all. This allows us to use a <open dir, NtQueryDirectoryFile, close dir> sequence for any directory that doesn't contain any possible matches, instead of having to use a separate look up for each individual filename combination (unappended + each PATHEXT appended). For directories where the wildcard *does* match something, we only need to do a maximum of <number of supported PATHEXT extensions> more NtQueryDirectoryFile calls. --- In addition, we now only evaluate the extensions in PATHEXT that we know we can handle (.COM, .EXE, .BAT, .CMD) and ignore the rest. --- This commit also makes two edge cases match Windows behavior: - If an app name has the extension .exe and it is attempted to be executed, that is now treated as unrecoverable and InvalidExe is immediately returned no matter where the .exe is (cwd or in the PATH). This matches the behavior of the Windows cmd.exe. - If the app name contains more than just a filename (e.g. it has path separators), then it is excluded from PATH searching and only does a cwd search. This matches the behavior of Windows cmd.exe.
A general-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
Resources
- Introduction
- Download & Documentation
- Chapter 0 - Getting Started | ZigLearn.org
- Community
- Contributing
- Code of Conduct
- Frequently Asked Questions
- Community Projects
Installation
- download a pre-built binary
- install from a package manager
- build from source
- bootstrap zig for any target
License
The ultimate goal of the Zig project is to serve users. As a first-order effect, this means users of the compiler, helping programmers to write better software. Even more important, however, are the end-users.
Zig is intended to be used to help end-users accomplish their goals. Zig should be used to empower end-users, never to exploit them financially, or to limit their freedom to interact with hardware or software in any way.
However, such problems are best solved with social norms, not with software licenses. Any attempt to complicate the software license of Zig would risk compromising the value Zig provides.
Therefore, Zig is available under the MIT (Expat) License, and comes with a humble request: use it to make software better serve the needs of end-users.
This project redistributes code from other projects, some of which have other licenses besides MIT. Such licenses are generally similar to the MIT license for practical purposes. See the subdirectories and files inside lib/ for more details.