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84c0f65446
In both the Unix and Windows variants, std::getenv was called and the result passed directly to a function accepting a StringRef. This isn't OK because it might return a null pointer and that causes the StringRef constructor to assert (and generally produces crash-prone code if asserts are disabled). Fix this by independently testing the result as non-null prior to splitting things. This in turn uncovered another bug in the Unix variant where it would infinitely recurse if PATH="", or after this fix if PATH isn't set. There is no need to recurse at all. Slightly re-arrange the code to make it clear that we can just fixup the Paths argument based on the environment if we find anything. I don't know of a particularly useful way to test these routines in LLVM. I'll commit a test to Clang that ensures that its driver correctly handles various settings of PATH. However, I have no idea how to correctly write a Windows test for the PATHEXT change. Any Windows developers who could provide such a test, please have at. =D Many thanks to Nick Lewycky and others for helping debug this. =/ It was quite nasty for us to track down. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223099 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