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548f2b6e8f
Owning the buffer is somewhat inflexible. Some Binaries have sub Binaries (like Archive) and we had to create dummy buffers just to handle that. It is also a bad fit for IRObjectFile where the Module wants to own the buffer too. Keeping this ownership would make supporting IR inside native objects particularly painful. This patch focuses in lib/Object. If something elsewhere used to own an Binary, now it also owns a MemoryBuffer. This patch introduces a few new types. * MemoryBufferRef. This is just a pair of StringRefs for the data and name. This is to MemoryBuffer as StringRef is to std::string. * OwningBinary. A combination of Binary and a MemoryBuffer. This is needed for convenience functions that take a filename and return both the buffer and the Binary using that buffer. The C api now uses OwningBinary to avoid any change in semantics. I will start a new thread to see if we want to change it and how. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216002 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