Improve TemporaryFile implementation for Windows (#736)

On Windows, multiple ccache process could race each other to create,
rename and delete temporary files, because they would attempt to
generate the same sequence of temporary file names
(`tmp.cpp_stdout.iG2Kb7`, `tmp.cpp_stdout.P1kAlM`,
`tmp.cpp_stdout.FzP5tM`, ...).

This is because ccache used mingw-w64's [implementation of mkstemp][1],
which uses `rand()` to generate temporary file names, and ccache was
never seeding the thread-local PRNG used by `rand()`.

Replace ccache's use of `mkstemp()` on Windows with an implementation
based on OpenBSD. This allows us to sidestep mingw-w64's problematic
implementation, and allows us to build using MSVC again. (MSVC's C
standard library does not provide `mkstemp()`.)

Example errors:

- Some ccache process is in the process of deleting a temporary file:

      ccache: error: Failed to create temporary file for C:\Users\someuser/.ccache/tmp/tmp.cpp_stdout.FzP5tM: Access is denied.

- Some ccache process has destination file open, so it can't be overwritten:

      ccache: error: failed to rename C:\Users\someuser/.ccache/tmp/tmp.cpp_stdout.iG2Kb7 to C:\Users\someuser/.ccache/tmp/tmp.cpp_stdout.iG2Kb7.ii: Access is denied.

- Source file has been deleted by some other ccache process:

      ccache: error: failed to rename C:\Users\someuser/.ccache/tmp/tmp.cpp_stdout.P1kAlM to C:\Users\someuser/.ccache/tmp/tmp.cpp_stdout.P1kAlM.ii: The system cannot find the file specified.

[1]: https://github.com/mirror/mingw-w64/blob/v8.0.0/mingw-w64-crt/misc/mkstemp.c

1 files changed, 24 insertions, 0 deletions

diff --git a/LICENSE.adoc b/LICENSE.adoc
index 3c15c572..a9e5b9da 100644
--- a/LICENSE.adoc
+++ b/LICENSE.adoc
@@ -638,6 +638,30 @@ The full license text can be found in LGPL-3.0.txt and at
 https://www.gnu.org/licenses/lgpl-3.0.html.
 
 
+src/third_party/win32/mktemp.*
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This implementation of `mkstemp()` for Win32 was adapted from
+<https://github.com/openbsd/src/blob/99b791d14c0f1858d87a0c33b55880fb9b00be66/lib/libc/stdio/mktemp.c>
+and has the folowing license text:
+
+-------------------------------------------------------------------------------
+Copyright (c) 1996-1998, 2008 Theo de Raadt
+Copyright (c) 1997, 2008-2009 Todd C. Miller
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+-------------------------------------------------------------------------------
+
 src/third_party/xxh*
 ~~~~~~~~~~~~~~~~~~~~