[llvm] r354209 - [LLVMSupport]: Remove a severely outdated README.

Kristina Brooks via llvm-commits llvm-commits at lists.llvm.org
Sat Feb 16 17:52:18 PST 2019

Author: kristina
Date: Sat Feb 16 17:52:18 2019
New Revision: 354209

URL: http://llvm.org/viewvc/llvm-project?rev=354209&view=rev
[LLVMSupport]: Remove a severely outdated README.

The LLVM Support library implementation has resided in
//llvm/lib/Support for a significant amount of time now,
with documentation having been updated with all references
to the "System library" being replaced with "Support library".

Since this file mirrors already existing documentation available
for Support library, includes dead links to documentation and
still refers to it as "System library", having it there is
confusing and updating it has very little point as it duplicates
information in documentation, except documentation is a lot more
up to date while this file has not been maintained.

Up to date documentation concerning this can be found here:


Removed: llvm/trunk/lib/Support/README.txt.system
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/README.txt.system?rev=354208&view=auto
--- llvm/trunk/lib/Support/README.txt.system (original)
+++ llvm/trunk/lib/Support/README.txt.system (removed)
@@ -1,43 +0,0 @@
-Design Of lib/System
-The software in this directory is designed to completely shield LLVM from any
-and all operating system specific functionality. It is not intended to be a
-complete operating system wrapper (such as ACE), but only to provide the
-functionality necessary to support LLVM.
-The software located here, of necessity, has very specific and stringent design
-rules. Violation of these rules means that cracks in the shield could form and
-the primary goal of the library is defeated. By consistently using this library,
-LLVM becomes more easily ported to new platforms since the only thing requiring
-porting is this library.
-Complete documentation for the library can be found in the file:
-  llvm/docs/SystemLibrary.html
-or at this URL:
-  http://llvm.org/docs/SystemLibrary.html
-While we recommend that you read the more detailed documentation, for the
-impatient, here's a high level summary of the library's requirements.
- 1. No system header files are to be exposed through the interface.
- 2. Std C++ and Std C header files are okay to be exposed through the interface.
- 3. No exposed system-specific functions.
- 4. No exposed system-specific data.
- 5. Data in lib/System classes must use only simple C++ intrinsic types.
- 6. Errors are handled by returning "true" and setting an optional std::string
- 7. Library must not throw any exceptions, period.
- 8. Interface functions must not have throw() specifications.
- 9. No duplicate function impementations are permitted within an operating
-    system class.
-To accomplish these requirements, the library has numerous design criteria that
-must be satisfied. Here's a high level summary of the library's design criteria:
- 1. No unused functionality (only what LLVM needs)
- 2. High-Level Interfaces
- 3. Use Opaque Classes
- 4. Common Implementations
- 5. Multiple Implementations
- 6. Minimize Memory Allocation
- 7. No Virtual Methods

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