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11a3aeeae3
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
Merged-In: I1e7d3a8820a79362245041251057fbeed2f7979b
Change-Id: I1e7d3a8820a79362245041251057fbeed2f7979b
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|---|---|---|
| adb | ||
| adf | ||
| base | ||
| bootstat | ||
| cpio | ||
| debuggerd | ||
| demangle | ||
| fastboot | ||
| fingerprintd | ||
| fs_mgr | ||
| gatekeeperd | ||
| healthd | ||
| include | ||
| init | ||
| libappfuse | ||
| libbacktrace | ||
| libbinderwrapper | ||
| libcrypto_utils | ||
| libcutils | ||
| libdiskconfig | ||
| libion | ||
| libkeyutils | ||
| liblog | ||
| libmemtrack | ||
| libmemunreachable | ||
| libmetricslogger | ||
| libnativebridge | ||
| libnativeloader | ||
| libnetutils | ||
| libpackagelistparser | ||
| libpixelflinger | ||
| libprocessgroup | ||
| libprocinfo | ||
| libsparse | ||
| libsuspend | ||
| libsync | ||
| libsystem | ||
| libsysutils | ||
| libunwindstack | ||
| libusbhost | ||
| libutils | ||
| libziparchive | ||
| lmkd | ||
| logcat | ||
| logd | ||
| logwrapper | ||
| mkbootimg | ||
| reboot | ||
| rootdir | ||
| run-as | ||
| sdcard | ||
| shell_and_utilities | ||
| toolbox | ||
| trusty | ||
| .clang-format | ||
| .clang-format-2 | ||
| .clang-format-4 | ||
| .gitignore | ||
| Android.bp | ||
| Android.mk | ||
| CleanSpec.mk | ||
| MODULE_LICENSE_APACHE2 | ||
| NOTICE | ||
| platform_tools_tool_version.mk | ||
| PREUPLOAD.cfg | ||