[llvm] r263749 - [Support] Add ExitOnError utility to support tools that use the exit-on-error
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 17 14:45:14 PDT 2016
On Thu, Mar 17, 2016 at 2:28 PM, Lang Hames via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: lhames
> Date: Thu Mar 17 16:28:49 2016
> New Revision: 263749
>
> URL: http://llvm.org/viewvc/llvm-project?rev=263749&view=rev
> Log:
> [Support] Add ExitOnError utility to support tools that use the
> exit-on-error
> idiom.
>
> Most LLVM tool code exits immediately when an error is encountered and
> prints an
> error message to stderr. The ExitOnError class supports this by providing
> two
> call operators - one for Errors, and one for Expected<T>s. Calls to code
> that
> can return Errors (or Expected<T>s) can use these calls to bail out on
> error,
> and otherwise continue as if the operation had succeeded. E.g.
>
> Error foo();
> Expected<int> bar();
>
> int main(int argc, char *argv[]) {
> ExitOnError ExitOnErr;
>
> ExitOnErr.setBanner(std::string("Error in ") + argv[0] + ":");
>
> // Exit if foo returns an error. No need to manually check error return.
> ExitOnErr(foo());
>
> // Exit if bar returns an error, otherwise unwrap the contained int and
> // continue.
> int X = ExitOnErr(bar());
>
> // ...
>
> return 0;
> }
>
>
> Modified:
> llvm/trunk/include/llvm/Support/Error.h
> llvm/trunk/unittests/Support/ErrorTest.cpp
>
> Modified: llvm/trunk/include/llvm/Support/Error.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Error.h?rev=263749&r1=263748&r2=263749&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/Error.h (original)
> +++ llvm/trunk/include/llvm/Support/Error.h Thu Mar 17 16:28:49 2016
> @@ -519,7 +519,8 @@ inline void handleAllErrors(Error E) {
> /// (allowing clean deallocation of resources, etc.), while reporting
> error
> /// information to the user.
> template <typename... HandlerTs>
> -void logAllUnhandledErrors(Error E, raw_ostream &OS, std::string
> ErrorBanner) {
> +void logAllUnhandledErrors(Error E, raw_ostream &OS,
> + const std::string &ErrorBanner) {
> if (!E)
> return;
> OS << ErrorBanner;
> @@ -742,6 +743,55 @@ inline std::error_code errorToErrorCode(
> return EC;
> }
>
> +/// Helper for check-and-exit error handling.
> +///
> +/// For tool use only. NOT FOR USE IN LIBRARY CODE.
> +///
> +class ExitOnError {
> +public:
> +
> + /// Create an error on exit helper.
> + ExitOnError(std::string Banner = "", int DefaultErrorExitCode = 1)
> + : Banner(Banner),
>
Missing std::move here ^
> + GetExitCode([=](const Error&) { return DefaultErrorExitCode; }) {}
> +
> + /// Set the banner string for any errors caught by operator().
>
Is there much need/benefit to being able to set the banner separately,
rather than just always on construction?
> + void setBanner(std::string Banner) {
> + this->Banner = Banner;
>
Missing std::move here ^
> + }
+
> + /// Set the exit-code mapper function.
> + void setExitCodeMapper(std::function<int(const Error&)> GetExitCode) {
> + this->GetExitCode = GetExitCode;
>
Missing std::move here ^
> + }
> +
> + /// Check Err. If it's in a failure state log the error(s) and exit.
> + void operator()(Error Err) const {
> + checkError(std::move(Err));
> + }
> +
> + /// Check E. If it's in a success state return the contained value. If
> it's
> + /// in a failure state log the error(s) and exit.
> + template <typename T>
> + T operator()(Expected<T> E) const {
> + checkError(E.takeError());
> + return std::move(*E);
>
Maybe take E by rvalue ref (since you're not moving it, just bits of it,
and T might be expensive to copy/non-movable)? Or do you need to be able to
pass copies/lvalues?
> + }
> +
> +private:
> +
> + void checkError(Error Err) const {
> + if (Err) {
> + int ExitCode = GetExitCode(Err);
> + logAllUnhandledErrors(std::move(Err), errs(), Banner);
> + exit(ExitCode);
> + }
> + }
> +
> + std::string Banner;
> + std::function<int(const Error&)> GetExitCode;
> +};
> +
> } // namespace llvm
>
> #endif // LLVM_SUPPORT_ERROR_H
>
> Modified: llvm/trunk/unittests/Support/ErrorTest.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/ErrorTest.cpp?rev=263749&r1=263748&r2=263749&view=diff
>
> ==============================================================================
> --- llvm/trunk/unittests/Support/ErrorTest.cpp (original)
> +++ llvm/trunk/unittests/Support/ErrorTest.cpp Thu Mar 17 16:28:49 2016
> @@ -38,6 +38,7 @@ namespace {
> // - consume_error to consume a "safe" error without any output.
> // - handleAllUnhandledErrors to assert that all errors are handled.
> // - logAllUnhandledErrors to log errors to a stream.
> +// - ExitOnError tests.
> //
> // Expected tests:
> // - Expected<T> with T.
> @@ -50,6 +51,7 @@ namespace {
> // - std::error_code to Error (ECError) in failure mode.
> // - Error to std::error_code in success mode.
> // - Error (ECError) to std::error_code in failure mode.
> +//
>
> // Custom error class with a default base class and some random 'info'
> attached.
> class CustomError : public ErrorInfo<CustomError> {
> @@ -376,6 +378,32 @@ TEST(Error, CheckErrorUtilities) {
> EXPECT_EQ(ErrorInfo, 7)
> << "Failed to handle Error returned from handleErrors.";
> }
> +
> + // Test ExitOnError
>
Probably good to pull it out into a separate test - more specific errors
from gtest/lit, and it means less repetition when running those EXPECT_EXIT
tests (each one has to be run in a separate process, and execute all the
preamble in the same test case until tehy reach the unique EXPECT_EXIT
they're intendting to run - so you might even consider splitting them out
even further)
> + {
> + ExitOnError ExitOnErr;
> + ExitOnErr.setBanner("Error in tool:");
> + ExitOnErr.setExitCodeMapper(
> + [](const Error &E) {
> + if (E.isA<CustomSubError>())
> + return 2;
> + return 1;
> + });
> +
> + // Make sure we don't bail on success.
> + ExitOnErr(Error::success());
> + EXPECT_EQ(ExitOnErr(Expected<int>(7)), 7)
> + << "exitOnError returned an invalid value for Expected";
> +
> + // Exit tests.
> + EXPECT_EXIT(ExitOnErr(make_error<CustomError>(7)),
> + ::testing::ExitedWithCode(1), "Error in tool:")
> + << "exitOnError returned an unexpected error result";
> +
> + EXPECT_EXIT(ExitOnErr(Expected<int>(make_error<CustomSubError>(0,
> 0))),
> + ::testing::ExitedWithCode(2), "Error in tool:")
> + << "exitOnError returned an unexpected error result";
> + }
> }
>
> // Test Expected behavior.
>
>
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