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4a03a9f089
Summary: I would like to add printing of registered targets to clang's version information. For this to work correctly, the VersionPrinter logic in CommandLine.cpp should support printing to arbitrary raw_ostreams, instead of always defaulting to outs(). Add a raw_ostream& parameter to the function pointer type used for VersionPrinter, and while doing so, introduce a typedef for convenience. Note that VersionPrinter::print() will still default to using outs(), the clang part will necessarily go into a separate review. Reviewers: beanz, chandlerc, dberris, mehdi_amini, zturner Reviewed By: mehdi_amini Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D33899 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304835 91177308-0d34-0410-b5e6-96231b3b80d8
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