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Treat permission_denied as no_such_file when stat'ing unit files #8577

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Treat permission_denied as no_such_file when stat'ing unit files #8577

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16 changes: 14 additions & 2 deletions clang/lib/Index/IndexUnitWriter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,17 @@ std::optional<bool> IndexUnitWriter::isUnitUpToDateForOutputFile(

llvm::sys::fs::file_status UnitStat;
if (std::error_code EC = llvm::sys::fs::status(UnitPath.c_str(), UnitStat)) {
if (EC != llvm::errc::no_such_file_or_directory) {
// On Windows, if a file is queried for attributes after another process marks that file for
// deletion but is still holding the file handle, the query will fail with a misleading
// "permission denied" error. This race happens frequently during index generation as many
// clang processes are racing to rename temporary index units to the same destination
// (incurring a delete on the destination file, which is queried in the status call just
// above). Seeing this error code here most likely means that the destination file is just
// marked for deletion, so treat it the same as a "no such file" error. A real permission
// error is unlikely, as the write to this file by another clang process would have already
// failed with "permission denied." Even if this error code is legitimate, the ensuing write
// will fail for the same reason.
if (EC != llvm::errc::no_such_file_or_directory && EC != llvm::errc::permission_denied) {
llvm::raw_string_ostream Err(Error);
Err << "could not access path '" << UnitPath
<< "': " << EC.message();
Expand All @@ -259,7 +269,9 @@ std::optional<bool> IndexUnitWriter::isUnitUpToDateForOutputFile(

llvm::sys::fs::file_status CompareStat;
if (std::error_code EC = llvm::sys::fs::status(*TimeCompareFilePath, CompareStat)) {
if (EC != llvm::errc::no_such_file_or_directory) {
// Treat permission denied errors the same as "no such file" errors, which the status function
// sometimes returns on Windows. See above for more detail.
if (EC != llvm::errc::no_such_file_or_directory && EC != llvm::errc::permission_denied) {
llvm::raw_string_ostream Err(Error);
Err << "could not access path '" << *TimeCompareFilePath
<< "': " << EC.message();
Expand Down