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9773c3dd6d
except for CompareAndSwap. That is the only one still being used anywhere now that statistics have been moved onto std::atomic. Also, add a warning to the header that we shouldn't introduce more uses of these old style atomics and instead should be using C++11's std::atomic facilities. Really hoping that we can hammer out the last couple of users here and replace them with something more localized and/or principled, but figured this was a pretty good start. =] Note that this patch will need to be reverted if r271504 needs to be reverted as that removes the last user of these. However, the biggest risk for that patch was MSVC 2013 and at least one bot has already passed where it would have failed there. I've tested MSVC 2015 using their web interfaces and other platforms seem fine, so I'm optimistic. Differential Revision: http://reviews.llvm.org/D20901 llvm-svn: 271540
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