clang doesn't make temporary files in all instances, causes build races by not using mk*temp(3) in /tmp

[Garrett Cooper]

On Tue, May 7, 2013 at 1:58 PM, Garrett Cooper <yaneurabeya at gmail.com> wrote:
> Hi Dimitriy,
>     I ran into the following error when trying to execute make
> tinderbox with FreeBSD svn head with ATF changes I'm going to push to
> benno@:
>
> cc  -O -pipe  -DHAVE_CONFIG_H
> -I/scratch/freebsd/head-svn/gnu/lib/libgomp -I.
> -I/scratch/freebsd/head-svn/gnu/lib/libgomp/../../../contrib/gcclibs/libgomp
> -I/scratch/freebsd/head-svn/gnu/lib/libgomp/../../../contrib/gcclibs/libgomp/config/posix
> -std=gnu99 -Qunused-arguments  -c
> /scratch/freebsd/head-svn/gnu/lib/libgomp/../../../contrib/gcclibs/libgomp/config/posix/bar.c
> -o bar.o
> cc: error: unable to make temporary file: /tmp/bar: can't make unique
> filename: Permission denied
> *** [bar.o] Error code 1
>
>     Did some poking around in the clang source and it looks like it's
> doing some less than intelligent things when generating "temporary"
> paths (from contrib/llvm/tools/clang/lib/Driver/Driver.cpp ):
>
> 1598 std::string Driver::GetTemporaryPath(StringRef Prefix, const char *Suffix)
> 1599   const {
> 1600   // FIXME: This is lame; sys::Path should provide this function
> (in particular,
> 1601   // it should know how to find the temporary files dir).
> 1602   std::string Error;
> 1603   const char *TmpDir = ::getenv("TMPDIR");
> 1604   if (!TmpDir)
> 1605     TmpDir = ::getenv("TEMP");
> 1606   if (!TmpDir)
> 1607     TmpDir = ::getenv("TMP");
> 1608   if (!TmpDir)
> 1609     TmpDir = "/tmp";
> 1610   llvm::sys::Path P(TmpDir);
> 1611   P.appendComponent(Prefix);
> 1612   if (P.makeUnique(false, &Error)) {
> 1613     Diag(clang::diag::err_unable_to_make_temp) << Error;
> 1614     return "";
> 1615   }
> 1616
> 1617   // FIXME: Grumble, makeUnique sometimes leaves the file around!?  PR3837.
> 1618   P.eraseFromDisk(false, 0);
> 1619
> 1620   if (Suffix)
> 1621     P.appendSuffix(Suffix);
> 1622   return P.str();
>
>     This logic (line 1612) is racy and incorrect.
>     This _needs_ to be fixed in clang to properly prefix and rename to
> the target path in the filesystem where the compilation is being done
> in order to avoid races with partial compilations, etc.

And I was pointed to these awesome bug reports by someone internal to
Isilon (thanks Anton!):

- http://lists.cs.uiuc.edu/pipermail/llvmbugs/2012-August/024524.html
- http://trac.macports.org/ticket/37834

It looks like the clang folks haven't fixed this issue yet. Arg..

Thanks,
-Garrett