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VS: Replace generation timestamp file atomically 

Since commit 34c882a9 (Allow VS 7 project Rebuild and Solution Rebuild to
work, 2007-11-10) we use a "CMakeFiles/generated.stamp" and some
associated files in the build tree to avoid re-running CMake when the
inputs have not changed but VS has cleaned the outputs it knows about.

When we do not really need to re-run we restore the generated.stamp file.
The non-re-run case can happen in multiple targets in parallel in VS >= 10
so we must restore the file atomically to avoid races.  Write the stamp
file to a random temporary name and then atomically rename it to the real
stamp file.
This commit is contained in:
Brad King 2013-02-12 10:46:22 -05:00
parent da6109df0f
commit 2dc17f88dd
1 changed files with 12 additions and 3 deletions
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15
Source/cmake.cxx
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@ -4033,10 +4033,18 @@ static bool cmakeCheckStampFile(const char* stampName)
}
// The build system is up to date. The stamp file has been removed
// by the VS IDE due to a "rebuild" request. Just restore it.
std::ofstream stamp(stampName);
// by the VS IDE due to a "rebuild" request. Restore it atomically.
cmOStringStream stampTempStream;
stampTempStream << stampName << ".tmp" << cmSystemTools::RandomSeed();
std::string stampTempString = stampTempStream.str();
const char* stampTemp = stampTempString.c_str();
{
// TODO: Teach cmGeneratedFileStream to use a random temp file (with
// multiple tries in unlikely case of conflict) and use that here.
std::ofstream stamp(stampTemp);
stamp << "# CMake generation timestamp file this directory.\n";
if(stamp)
}
if(cmSystemTools::RenameFile(stampTemp, stampName))
{
// Notify the user why CMake is not re-running. It is safe to
// just print to stdout here because this code is only reachable
@ -4047,6 +4055,7 @@ static bool cmakeCheckStampFile(const char* stampName)
}
else
{
cmSystemTools::RemoveFile(stampTemp);
cmSystemTools::Error("Cannot restore timestamp ", stampName);
return false;
}