[llvm] r176226 - [PathV2] In llvm::sys::fs::unique_file, make sure it doesn't fall into an infinite loop by constantly trying

[Robinson, Paul]

We ran into a case in this area on Windows a while back, just haven't gotten around to delivering it upstream.
I'll bump it up on my list.
--paulr

From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Argyrios Kyrtzidis
Sent: Wednesday, February 27, 2013 6:19 PM
To: Aaron Ballman
Cc: llvm-commits
Subject: Re: [llvm] r176226 - [PathV2] In llvm::sys::fs::unique_file, make sure it doesn't fall into an infinite loop by constantly trying

On Feb 27, 2013, at 4:42 PM, Aaron Ballman <aaron at aaronballman.com<mailto:aaron at aaronballman.com>> wrote:


Can we fall into the same trap in the Windows version of this code too?

I don't have a windows machine to test.
For anyone interested, the way I tested the fix was like this:

$ mkdir temp
$ cd temp
$ touch empty.c
$ lldb -- /path/to/clang -cc1 empty.c -emit-pch -o empty.pch
(stop at the "rety_open_create:" label of unique_file function)

Now delete 'temp' directory and make sure the function does not get stuck.

-Argyrios



~Aaron

On Wed, Feb 27, 2013 at 7:38 PM, Argyrios Kyrtzidis <akyrtzi at gmail.com<mailto:akyrtzi at gmail.com>> wrote:

Author: akirtzidis
Date: Wed Feb 27 18:38:19 2013
New Revision: 176226

URL: http://llvm.org/viewvc/llvm-project?rev=176226&view=rev
Log:
[PathV2] In llvm::sys::fs::unique_file, make sure it doesn't fall into an infinite loop by constantly trying
to create the parent path.

This can happen if the path is a relative filename and the current directory was removed.
Thanks to Daniel D. for the hint in fixing it.

Modified:
   llvm/trunk/lib/Support/Unix/PathV2.inc

Modified: llvm/trunk/lib/Support/Unix/PathV2.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/PathV2.inc?rev=176226&r1=176225&r2=176226&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Unix/PathV2.inc (original)
+++ llvm/trunk/lib/Support/Unix/PathV2.inc Wed Feb 27 18:38:19 2013
@@ -417,6 +417,10 @@ retry_random_path:
      RandomPath[i] = "0123456789abcdef"[sys::Process::GetRandomNumber() & 15];
  }

+  // Make sure we don't fall into an infinite loop by constantly trying
+  // to create the parent path.
+  bool TriedToCreateParent = false;
+
  // Try to open + create the file.
rety_open_create:
  int RandomFD = ::open(RandomPath.c_str(), O_RDWR | O_CREAT | O_EXCL, mode);
@@ -427,7 +431,9 @@ rety_open_create:
      goto retry_random_path;
    // If path prefix doesn't exist, try to create it.
    if (SavedErrno == errc::no_such_file_or_directory &&
-        !exists(path::parent_path(RandomPath))) {
+        !exists(path::parent_path(RandomPath)) &&
+        !TriedToCreateParent) {
+      TriedToCreateParent = true;
      StringRef p(RandomPath);
      SmallString<64> dir_to_create;
      for (path::const_iterator i = path::begin(p),


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