[LLVMdev] Driver::GetProgramPath is unable to find programs with file extension in name

[Oleg Ranevskyy]

Hello,

We are having a problem with linker lookup on Windows.

When the driver tries to locate a program by its name, e.g. a linker, it 
scans the paths provided by the toolchain using ScanDirForExecutable and 
then, if fails, uses llvm::sys::findProgramByName, which on Windows 
searches the CWD and system path. ScanDirForExecutable disregards file 
extensions, so search in the toolchain-provided dirs on Windows fails. 
llvm::sys::findProgramByName is aware of extensions via the "PATHEXT" 
env variable (it also has ".exe" hardcoded). However, our linker is not 
in the CWD or system path, thus search fails.

ScanDirForExecutable should respect file extenstions like 
findProgramByName does. One way of doing so is to make the system 
dependent llvm::sys::path::access function aware of extensions similarly 
to findProgramByName. Or the whole ScanDirForExecutable can be made 
system dependent and add an extension on Windows before passing the path 
to llvm::sys::fs::can_execute.

Does such a patch look reasonable? Any opinions / ideas will be much 
appreciated.

Thanks.
Kind regards,
Oleg