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Merged
merged 2 commits into from
Aug 21, 2025
Merged

Improve temporary file location for atomic writes #1477

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be6762e
(156721664) Temporary files for atomic writes should use _amkrtemp in…
jmschonfeld Aug 13, 2025
bfa7692
Fix build failure
jmschonfeld Aug 21, 2025
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49 changes: 39 additions & 10 deletions Sources/FoundationEssentials/Data/Data+Writing.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -157,9 +157,37 @@ private func createTemporaryFile(at destinationPath: String, inPath: PathOrURL,

let pidString = String(ProcessInfo.processInfo.processIdentifier, radix: 16, uppercase: true)
let template = directoryPath + prefix + pidString + ".XXXXXX"
var count = 0
let maxCount = 7
repeat {
for _ in 0 ..< maxCount {
#if FOUNDATION_FRAMEWORK
let (sandboxResult, amkrErrno) = inPath.withFileSystemRepresentation { inPathFileSystemRep -> ((Int32, String)?, Int32?) in
guard let inPathFileSystemRep else {
return (nil, nil)
}
// First, try _amkrtemp to carry over any sandbox extensions for inPath to the temporary file (even if the application isn't sandboxed)
guard let uniqueTempFile = _amkrtemp(inPathFileSystemRep) else {
return (nil, errno)
}
defer { free(uniqueTempFile) }
let fd = openFileDescriptorProtected(path: uniqueTempFile, flags: O_CREAT | O_EXCL | O_RDWR, options: options)
if fd >= 0 {
// Got a good fd
return ((fd, String(cString: uniqueTempFile)), nil)
}
return (nil, errno)
}

// If _amkrtemp succeeded, return its result
if let sandboxResult {
return sandboxResult
}
// If _amkrtemp failed with EEXIST, just retry
if amkrErrno == EEXIST {
continue
}
// Otherwise, fall through to mktemp below
#endif

let result = try template.withMutableFileSystemRepresentation { templateFileSystemRep -> (Int32, String)? in
guard let templateFileSystemRep else {
throw CocoaError(.fileWriteInvalidFileName)
Expand Down Expand Up @@ -187,7 +215,12 @@ private func createTemporaryFile(at destinationPath: String, inPath: PathOrURL,

// If the file exists, we repeat. Otherwise throw the error.
if errno != EEXIST {
throw CocoaError.errorWithFilePath(inPath, errno: errno, reading: false, variant: variant)
#if FOUNDATION_FRAMEWORK
let debugDescription = "Creating a temporary file via mktemp failed. Creating the temporary file via _amkrtemp previously also failed with errno \(amkrErrno)"
#else
let debugDescription: String? = nil
#endif
throw CocoaError.errorWithFilePath(inPath, errno: errno, reading: false, variant: variant, debugDescription: debugDescription)
}

// Try again
Expand All @@ -196,14 +229,10 @@ private func createTemporaryFile(at destinationPath: String, inPath: PathOrURL,

if let result {
return result
} else {
count += 1
if count > maxCount {
// Prevent an infinite loop; even if the error is obscure
throw CocoaError(.fileWriteUnknown)
}
}
} while true
}
// We hit max count, prevent an infinite loop; even if the error is obscure
throw CocoaError(.fileWriteUnknown)
#endif // os(WASI)
}

Expand Down
52 changes: 30 additions & 22 deletions Sources/FoundationEssentials/Error/CocoaError+FilePath.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -31,12 +31,12 @@ import WinSDK
// MARK: - Error Creation with CocoaError.Code

extension CocoaError {
static func errorWithFilePath(_ code: CocoaError.Code, _ path: String, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
CocoaError(code, path: path, variant: variant, source: source, destination: destination)
static func errorWithFilePath(_ code: CocoaError.Code, _ path: String, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
CocoaError(code, path: path, variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}

static func errorWithFilePath(_ code: CocoaError.Code, _ url: URL, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
CocoaError(code, url: url, variant: variant, source: source, destination: destination)
static func errorWithFilePath(_ code: CocoaError.Code, _ url: URL, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
CocoaError(code, url: url, variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}
}

Expand Down Expand Up @@ -81,21 +81,21 @@ extension POSIXError {
}

extension CocoaError {
static func errorWithFilePath(_ pathOrURL: PathOrURL, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
static func errorWithFilePath(_ pathOrURL: PathOrURL, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
switch pathOrURL {
case .path(let path):
return Self.errorWithFilePath(path, errno: errno, reading: reading, variant: variant, source: source, destination: destination)
return Self.errorWithFilePath(path, errno: errno, reading: reading, variant: variant, source: source, destination: destination, debugDescription: debugDescription)
case .url(let url):
return Self.errorWithFilePath(url, errno: errno, reading: reading, variant: variant, source: source, destination: destination)
return Self.errorWithFilePath(url, errno: errno, reading: reading, variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}
}

static func errorWithFilePath(_ path: String, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
CocoaError(Code(fileErrno: errno, reading: reading), path: path, underlying: POSIXError(errno: errno), variant: variant, source: source, destination: destination)
static func errorWithFilePath(_ path: String, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
CocoaError(Code(fileErrno: errno, reading: reading), path: path, underlying: POSIXError(errno: errno), variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}

static func errorWithFilePath(_ url: URL, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
CocoaError(Code(fileErrno: errno, reading: reading), url: url, underlying: POSIXError(errno: errno), variant: variant, source: source, destination: destination)
static func errorWithFilePath(_ url: URL, errno: Int32, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
CocoaError(Code(fileErrno: errno, reading: reading), url: url, underlying: POSIXError(errno: errno), variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}
}

Expand Down Expand Up @@ -144,18 +144,18 @@ extension CocoaError.Code {
}

extension CocoaError {
static func errorWithFilePath(_ path: PathOrURL, win32 dwError: DWORD, reading: Bool) -> CocoaError {
static func errorWithFilePath(_ path: PathOrURL, win32 dwError: DWORD, reading: Bool, debugDescription: String? = nil) -> CocoaError {
switch path {
case let .path(path):
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: path.isEmpty), path: path, underlying: Win32Error(dwError))
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: path.isEmpty), path: path, underlying: Win32Error(dwError), debugDescription: debugDescription)
case let .url(url):
let pathStr = url.withUnsafeFileSystemRepresentation { String(cString: $0!) }
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: pathStr.isEmpty), path: pathStr, url: url, underlying: Win32Error(dwError))
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: pathStr.isEmpty), path: pathStr, url: url, underlying: Win32Error(dwError), debugDescription: debugDescription)
}
}

static func errorWithFilePath(_ path: String? = nil, win32 dwError: DWORD, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil) -> CocoaError {
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: path?.isEmpty), path: path, underlying: Win32Error(dwError), variant: variant, source: source, destination: destination)
static func errorWithFilePath(_ path: String? = nil, win32 dwError: DWORD, reading: Bool, variant: String? = nil, source: String? = nil, destination: String? = nil, debugDescription: String? = nil) -> CocoaError {
return CocoaError(.init(win32: dwError, reading: reading, emptyPath: path?.isEmpty), path: path, underlying: Win32Error(dwError), variant: variant, source: source, destination: destination, debugDescription: debugDescription)
}
}
#endif
Expand Down Expand Up @@ -190,7 +190,8 @@ extension CocoaError {
underlying: (some Error)? = Optional<CocoaError>.none,
variant: String? = nil,
source: String? = nil,
destination: String? = nil
destination: String? = nil,
debugDescription: String? = nil
) {
self.init(
code,
Expand All @@ -199,7 +200,8 @@ extension CocoaError {
underlying: underlying,
variant: variant,
source: source,
destination: destination
destination: destination,
debugDescription: debugDescription
)
}

Expand All @@ -209,7 +211,8 @@ extension CocoaError {
underlying: (some Error)? = Optional<CocoaError>.none,
variant: String? = nil,
source: String? = nil,
destination: String? = nil
destination: String? = nil,
debugDescription: String? = nil
) {
self.init(
code,
Expand All @@ -218,7 +221,8 @@ extension CocoaError {
underlying: underlying,
variant: variant,
source: source,
destination: destination
destination: destination,
debugDescription: debugDescription
)
}

Expand All @@ -229,10 +233,11 @@ extension CocoaError {
underlying: (some Error)? = Optional<CocoaError>.none,
variant: String? = nil,
source: String? = nil,
destination: String? = nil
destination: String? = nil,
debugDescription: String? = nil
) {
#if FOUNDATION_FRAMEWORK
self.init(_uncheckedNSError: NSError._cocoaError(withCode: code.rawValue, path: path, url: url, underlying: underlying, variant: variant, source: source, destination: destination) as NSError)
self.init(_uncheckedNSError: NSError._cocoaError(withCode: code.rawValue, path: path, url: url, underlying: underlying, variant: variant, source: source, destination: destination, debugDescription: debugDescription) as NSError)
#else
var userInfo: [String : Any] = [:]
if let path {
Expand All @@ -253,6 +258,9 @@ extension CocoaError {
if let variant {
userInfo[NSUserStringVariantErrorKey] = [variant]
}
if let debugDescription {
userInfo[NSDebugDescriptionErrorKey] = debugDescription
}

self.init(code, userInfo: userInfo)
#endif
Expand Down