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f6411a2366
As the intended use for LaunchError::mFunction is telemetry, avoid the possibility of accidental exfiltration of PII by requiring that LaunchError be constructed from `StaticString`. Additionally, remove the Windows-specific constructor overloads in favor of an explicit factory function, and explicitly document that `mError` is a generic bag of bits rather than any kind of strict error type. No functional changes. Differential Revision: https://phabricator.services.mozilla.com/D209712
71 lines
2.6 KiB
C++
71 lines
2.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_ipc_LaunchError_h
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#define mozilla_ipc_LaunchError_h
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#include "mozilla/StaticString.h"
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#include "nsError.h" // for nsresult
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#if defined(XP_WIN)
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# include <windows.h>
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# include <winerror.h>
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#endif
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namespace mozilla::ipc {
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class LaunchError {
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public:
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// The context of an error code (at the very least, the function that emitted
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// it and where it was called) is fundamentally necessary to interpret its
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// value. Since we should have that, we're not too fussed about integral
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// coercions, so long as we don't lose any bits.
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//
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// Under POSIX, the usual OS-error type is `int`. Under Windows, the usual
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// error type is `HRESULT`, which (despite having bitfield semantics) is
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// ultimately a typedef for a flavor of (signed) `long`. For simplicity, and
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// in the absence of other constraints, our "error type" container is simply
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// the join of these two.
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using ErrorType = long;
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// Constructor.
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//
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// The default of `0` is intended for failure cases where we don't have an
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// error code -- usually because the function we've called to determine
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// failure has only a boolean return, but also for when we've detected some
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// internal failure and there's no appropriate `nsresult` for it.
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explicit LaunchError(StaticString aFunction, ErrorType aError = 0)
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: mFunction(aFunction), mError(aError) {}
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#ifdef WIN32
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// The error code returned by ::GetLastError() is (usually) not an HRESULT.
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// This convenience-function maps its return values to the segment of
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// HRESULT's namespace reserved for that.
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//
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// This is not formally necessary -- the error location should suffice to
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// disambiguate -- but it's nice to have it converted when reading through
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// error-values: `0x80070005` is marginally more human-meaningful than `5`.
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static LaunchError FromWin32Error(StaticString aFunction, DWORD aError) {
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return LaunchError(aFunction, HRESULT_FROM_WIN32(aError));
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}
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#endif
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// By design, `nsresult` does not implicitly coerce to an integer.
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LaunchError(StaticString aFunction, nsresult aError)
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: mFunction(aFunction), mError((ErrorType)aError) {}
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StaticString FunctionName() const { return mFunction; }
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ErrorType ErrorCode() const { return mError; }
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private:
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StaticString mFunction;
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ErrorType mError;
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};
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} // namespace mozilla::ipc
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#endif // ifndef mozilla_ipc_LaunchError_h
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