[llvm-objcopy] Make .build-id linking atomic
This change makes linking into .build-id atomic and safe to use.
Some users under particular workflows are reporting that this races
more than half the time under particular conditions.
llvm-svn: 356404
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 202248c..902df74 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -169,25 +169,6 @@
SmallVectorImpl<char> &ResultPath, bool MakeAbsolute,
unsigned Mode, FSEntity Type,
sys::fs::OpenFlags Flags = sys::fs::OF_None) {
- SmallString<128> ModelStorage;
- Model.toVector(ModelStorage);
-
- if (MakeAbsolute) {
- // Make model absolute by prepending a temp directory if it's not already.
- if (!sys::path::is_absolute(Twine(ModelStorage))) {
- SmallString<128> TDir;
- sys::path::system_temp_directory(true, TDir);
- sys::path::append(TDir, Twine(ModelStorage));
- ModelStorage.swap(TDir);
- }
- }
-
- // From here on, DO NOT modify model. It may be needed if the randomly chosen
- // path already exists.
- ResultPath = ModelStorage;
- // Null terminate.
- ResultPath.push_back(0);
- ResultPath.pop_back();
// Limit the number of attempts we make, so that we don't infinite loop. E.g.
// "permission denied" could be for a specific file (so we retry with a
@@ -195,13 +176,7 @@
// Checking which is racy, so we try a number of times, then give up.
std::error_code EC;
for (int Retries = 128; Retries > 0; --Retries) {
- // Replace '%' with random chars.
- for (unsigned i = 0, e = ModelStorage.size(); i != e; ++i) {
- if (ModelStorage[i] == '%')
- ResultPath[i] =
- "0123456789abcdef"[sys::Process::GetRandomNumber() & 15];
- }
-
+ sys::fs::createUniquePath(Model, ResultPath, MakeAbsolute);
// Try to open + create the file.
switch (Type) {
case FS_File: {
@@ -762,6 +737,32 @@
return std::error_code();
}
+void createUniquePath(const Twine &Model, SmallVectorImpl<char> &ResultPath,
+ bool MakeAbsolute) {
+ SmallString<128> ModelStorage;
+ Model.toVector(ModelStorage);
+
+ if (MakeAbsolute) {
+ // Make model absolute by prepending a temp directory if it's not already.
+ if (!sys::path::is_absolute(Twine(ModelStorage))) {
+ SmallString<128> TDir;
+ sys::path::system_temp_directory(true, TDir);
+ sys::path::append(TDir, Twine(ModelStorage));
+ ModelStorage.swap(TDir);
+ }
+ }
+
+ ResultPath = ModelStorage;
+ ResultPath.push_back(0);
+ ResultPath.pop_back();
+
+ // Replace '%' with random chars.
+ for (unsigned i = 0, e = ModelStorage.size(); i != e; ++i) {
+ if (ModelStorage[i] == '%')
+ ResultPath[i] = "0123456789abcdef"[sys::Process::GetRandomNumber() & 15];
+ }
+}
+
std::error_code createUniqueFile(const Twine &Model, int &ResultFd,
SmallVectorImpl<char> &ResultPath,
unsigned Mode) {