[LLVMdev] The Next Win32 File System Problem

[Jeff Cohen]

Yep, you found another bug.  Unlike Unix, Windows does not allow a file 
to be implicitly replaced via renaming.  I'll fix it.

Greg Pettyjohn wrote:
> Fixing one bug uncovers the next one...
>
> To reproduce:
>  llvm-ar  rc ./libgcc.a libgcc/./_muldi3.o <and-lots-more-.o-files...>
>
> The result:
>   C:\msys\1.0\home\llvm_home\install\bin\llvm-ar.exe: Can't move './libgcc.a-000003' to './libgcc.a-000002': Cannot create a file when that file already exists.
>
> So apparently, we're trying to move one file on top of another.
>
> The error is generated in:
>
> Path::renamePathOnDisk(const Path& newName) {
>   if (!MoveFile(path.c_str(), newName.c_str()))
>     ThrowError("Can't move '" + path +
>                "' to '" + newName.path + "': ");
>   return true;
> }
>
> I'm guessing that the last part of the error message ("Cannot create a
> file when that file already exists") is the result of a GetLastError() ?
>
> Here's a stack trace just before the exception is thrown:
> Breakpoint 1, llvm::sys::Path::renamePathOnDisk(llvm::sys::Path const&) (
>     this=0x22fc00, newName=@0x22fd20)
>     at
> C:/msys/1.0/home/llvm_home/llvm-build/../llvm/lib/System/Win32/Path.inc:685
> 685       if (!MoveFile(path.c_str(), newName.c_str()))
> (gdb) n
> 686         ThrowError("Can't move '" + path +
> (gdb) bt
> #0  llvm::sys::Path::renamePathOnDisk(llvm::sys::Path const&)
> (this=0x22fc00,
>     newName=@0x22fd20)
>     at
> C:/msys/1.0/home/llvm_home/llvm-build/../llvm/lib/System/Win32/Path.inc:686
> #1  0x004871c3 in llvm::Archive::writeToDisk(bool, bool, bool)
> (this=0x3d5110,
>     CreateSymbolTable=true, TruncateNames=false, Compress=false)
>     at
> C:/msys/1.0/home/llvm_home/llvm-build/../llvm/lib/Bytecode/Archive/ArchiveWriter.cpp:461
> #2  0x00403d4d in doReplaceOrInsert() ()
>     at
> C:/msys/1.0/home/llvm_home/llvm-build/../llvm/tools/llvm-ar/llvm-ar.cpp:645
> #3  0x004042b5 in main (argc=64, argv=0x3d4ca0)
>     at
> C:/msys/1.0/home/llvm_home/llvm-build/../llvm/tools/llvm-ar/llvm-ar.cpp:704
> (gdb)
>
>
> So how to fix this?:
> 1. These are both temp files right? Why are we trying to overwrite an
> existing file during a MoveFile? Can we just choose a different temp file
> name that doesn't exist yet?
>
> 2. Is it deliberate? Should we be deleting the target file and then
> performing the MoveFile?
>
>
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>
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