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By default, the GraphWriter code assumes that the generic file open program (`open` on Apple, `xdg-open` on other systems) can wait on the forked proces to complete. When the fork ends, the code would delete the temporary dot files created, and return. On GNU/Linux, the xdg-open program does not have a "wait for your fork to complete before dying" option. So the behaviour was that xdg-open would launch a process, quickly die itself, and then the GraphWriter code would think its OK to quickly delete all the temporary files. Once the temporary files were deleted, the dot viewers would get very upset, and often give you weird errors. This change only waits on the generic open program on Apple platforms. Elsewhere, we don't wait on the process, and hence we don't try and clean up the temporary files. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241250 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