[PATCH] D64939: Add a proposal for a libc project under the LLVM umbrella.

[Siva Chandra via Phabricator via llvm-commits]

sivachandra created this revision.
sivachandra added reviewers: chandlerc, dlj, echristo, hfinkel, jfb, zturner.
Herald added subscribers: llvm-commits, dexonsmith.
Herald added a project: LLVM.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D64939

Files:
  llvm/docs/Proposals/LLVMLibC.rst


Index: llvm/docs/Proposals/LLVMLibC.rst
===================================================================
--- /dev/null
+++ llvm/docs/Proposals/LLVMLibC.rst
@@ -0,0 +1,93 @@
+==============================
+"llvm-libc" C Standard Library
+==============================
+
+.. contents:: Table of Contents
+  :depth: 4
+  :local:
+
+Introduction
+============
+
+This is a proposal to start *llvm-libc*, an implementation of the
+C standard library targeting C17 and above, as part of the LLVM project.
+llvm-libc will also provide platform specific extensions as relevant.
+For example, on Linux it also provides pthreads, librt and other POSIX
+extension libraries.
+
+Features
+========
+
+llvm-libc will be developed to have a certain minimum set of features:
+
+- C17 and upwards conformant. Since the C17 standard is only a bugfix
+  upgrade of the C11 standard, llvm-libc is effectively C11 and
+  upwards conformant.
+- A modular libc with individual pieces implemented in the "as a
+  library" philosophy of the LLVM project.
+- Ability to layer this libc over the system libc.
+- Provide C symbols as specified by the standards, but take advantage
+  and use C++ language facilities for the core implementation.
+- Provides POSIX extensions on POSIX compliant platforms.
+- Provides system-specific extensions as appropriate. For example,
+  provides the Linux API on Linux.
+- Vendor extensions if and only if necessary.
+- Designed and developed from the start to work with LLVM tooling and
+  testing like fuzz testing and sanitizer-supported testing.
+- ABI independent implementation as far as possible.
+- Use source based implementations as far possible rather than
+  assembly. Will try to *fix* the compiler rather than use assembly
+  language workarounds.
+- Extensive unit testing and standards conformance testing. If relevant
+  and possible, differential testing: We want to be able
+  to test llvm-libc against another battle-tested libc. This is
+  essentially to understand how we differ from other libcs. Also if
+  relevant and possible, test against the testsuite of an another
+  battle-tested libc implementation.
+
+Why a new C Standard Library?
+=============================
+
+Implementing a libc is no small task and is not be taken lightly. A
+natural question to ask is, "why a new implementation of the C
+standard library?" There is no single answer to this question, but
+some of the major reasons are as follows:
+
+- Most libc implementations are monolithic. It is a non-trivial
+  porting task to pick and choose only the pieces relevant to one's
+  platform. The llvm-libc will be developed with sufficient modularity to
+  make picking and choosing a straightforward task.
+- Most libc implementations break when built with sanitizer specific
+  compiler options. The llvm-libc will be developed from the start to
+  work with those specialized compiler options.
+- The llvm-libc will be developed to support and employ fuzz testing
+  from the start.
+- Most libc implementations use a good amount of assembly language,
+  and assume specific ABIs (may be platform dependent). With the llvm-libc
+  implementation, we want to use normal source code as much as possible so
+  that compiler-based changes to the ABI are easy. Moreover, as part of the
+  LLVM project, we want to use this opportunity to fix performance related
+  compiler bugs rather than using assembly workarounds.
+- A large hole in the llvm toolchain will be plugged with llvm-libc.
+  With the broad platform expertise in the LLVM community, and the
+  strong license and project structure, we think that llvm-libc will
+  be more tunable and robust, without sacrificing the simplicity and
+  accessibility typical of the LLVM project.
+
+Platform Support
+================
+
+We envision that llvm-libc will support a variety of platforms in the coming
+years. Interested parties are encouraged to participate in the design and
+implementation, and add support for their favorite platforms.
+
+Current Status
+==============
+
+llvm-libc development is still in the planning phase.
+
+Build Bots
+==========
+
+Once the development starts, there will be llvm-libc focused builders added to
+the LLVM BuildBot.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D64939.210640.patch
Type: text/x-patch
Size: 4231 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190718/adcfdddf/attachment.bin>