Introduce a flag in SourceManager to treat non-system source files
as "volatile", meaning there's a high enough chance that they may
change while we are trying to use them.
This flag is only enabled by libclang.
Currently "volatile" source files will be stat'ed immediately
before opening them, because the file size stat info
may not be accurate since when we got it (e.g. from the PCH).
This avoids crashes when trying to reference mmap'ed memory
from a file whose size is not what we expect.
Note that there's still a window for a racing issue to occur
but the window for it should be way smaller than before.
We can consider later on to avoid mmap completely on such files.
rdar://11612916
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160074 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/FileManager.cpp b/lib/Basic/FileManager.cpp
index ddf8934..b921f3e 100644
--- a/lib/Basic/FileManager.cpp
+++ b/lib/Basic/FileManager.cpp
@@ -488,15 +488,21 @@
}
llvm::MemoryBuffer *FileManager::
-getBufferForFile(const FileEntry *Entry, std::string *ErrorStr) {
+getBufferForFile(const FileEntry *Entry, std::string *ErrorStr,
+ bool isVolatile) {
OwningPtr<llvm::MemoryBuffer> Result;
llvm::error_code ec;
+ uint64_t FileSize = Entry->getSize();
+ // If there's a high enough chance that the file have changed since we
+ // got its size, force a stat before opening it.
+ if (isVolatile)
+ FileSize = -1;
+
const char *Filename = Entry->getName();
// If the file is already open, use the open file descriptor.
if (Entry->FD != -1) {
- ec = llvm::MemoryBuffer::getOpenFile(Entry->FD, Filename, Result,
- Entry->getSize());
+ ec = llvm::MemoryBuffer::getOpenFile(Entry->FD, Filename, Result, FileSize);
if (ErrorStr)
*ErrorStr = ec.message();
@@ -508,7 +514,7 @@
// Otherwise, open the file.
if (FileSystemOpts.WorkingDir.empty()) {
- ec = llvm::MemoryBuffer::getFile(Filename, Result, Entry->getSize());
+ ec = llvm::MemoryBuffer::getFile(Filename, Result, FileSize);
if (ec && ErrorStr)
*ErrorStr = ec.message();
return Result.take();
@@ -516,7 +522,7 @@
SmallString<128> FilePath(Entry->getName());
FixupRelativePath(FilePath);
- ec = llvm::MemoryBuffer::getFile(FilePath.str(), Result, Entry->getSize());
+ ec = llvm::MemoryBuffer::getFile(FilePath.str(), Result, FileSize);
if (ec && ErrorStr)
*ErrorStr = ec.message();
return Result.take();