init tries to propagate error information up to build context before
logging errors. This is a good thing, however too often init has the
overly verbose paradigm for error handling, below:
bool CalculateResult(const T& input, U* output, std::string* err)
bool CalculateAndUseResult(const T& input, std::string* err) {
U output;
std::string calculate_result_err;
if (!CalculateResult(input, &output, &calculate_result_err)) {
*err = "CalculateResult " + input + " failed: " +
calculate_result_err;
return false;
}
UseResult(output);
return true;
}
Even more common are functions that return only true/false but also
require passing a std::string* err in order to see the error message.
This change introduces a Result<T> that is use to either hold a
successful return value of type T or to hold an error message as a
std::string. If the functional only returns success or a failure with
an error message, Result<Success> may be used. The classes Error and
ErrnoError are used to indicate a failed Result<T>.
A successful Result<T> is constructed implicitly from any type that
can be implicitly converted to T or from the constructor arguments for
T. This allows you to return a type T directly from a function that
returns Result<T>.
Error and ErrnoError are used to construct a Result<T> has
failed. Each of these classes take an ostream as an input and are
implicitly cast to a Result<T> containing that failure. ErrnoError()
additionally appends ": " + strerror(errno) to the end of the failure
string to aid in interacting with C APIs.
The end result is that the above code snippet is turned into the much
clearer example below:
Result<U> CalculateResult(const T& input);
Result<Success> CalculateAndUseResult(const T& input) {
auto output = CalculateResult(input);
if (!output) {
return Error() << "CalculateResult " << input << " failed: "
<< output.error();
}
UseResult(*output);
return Success();
}
This change also makes this conversion for some of the util.cpp
functions that used the old paradigm.
Test: boot bullhead, init unit tests
Change-Id: I1e7d3a8820a79362245041251057fbeed2f7979b
This change splits out the selinux initialization and supporting
functionality into selinux.cpp and splits the security related
initialization of the rng, etc to security.cpp. It also provides
additional documentation for SEPolicy loading as this has been
requested by some teams.
It additionally cleans up sehandle and sehandle_prop. The former is
static within selinux.cpp and new wrapper functions are created around
selabel_lookup*() to better serve the users. The latter is moved to
property_service.cpp as it is isolated to that file for its usage.
Test: boot bullhead
Merged-In: Idc95d493cebc681fbe686b5160502f36af149f60
Change-Id: Idc95d493cebc681fbe686b5160502f36af149f60
(cherry picked from commit 9afb86b25d8675927cb37c86119a7ecf19f74819)
Tom Cherry