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268 lines
9.2 KiB
268 lines
9.2 KiB
// AsmJit - Machine code generation for C++
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//
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// * Official AsmJit Home Page: https://asmjit.com
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// * Official Github Repository: https://github.com/asmjit/asmjit
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//
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// Copyright (c) 2008-2020 The AsmJit Authors
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//
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// This software is provided 'as-is', without any express or implied
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// warranty. In no event will the authors be held liable for any damages
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// arising from the use of this software.
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//
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// Permission is granted to anyone to use this software for any purpose,
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// including commercial applications, and to alter it and redistribute it
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// freely, subject to the following restrictions:
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//
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// 1. The origin of this software must not be misrepresented; you must not
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// claim that you wrote the original software. If you use this software
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// in a product, an acknowledgment in the product documentation would be
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// appreciated but is not required.
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// 2. Altered source versions must be plainly marked as such, and must not be
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// misrepresented as being the original software.
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// 3. This notice may not be removed or altered from any source distribution.
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#ifndef ASMJIT_CORE_ERRORHANDLER_H_INCLUDED
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#define ASMJIT_CORE_ERRORHANDLER_H_INCLUDED
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#include "../core/globals.h"
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ASMJIT_BEGIN_NAMESPACE
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//! \addtogroup asmjit_error_handling
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//! \{
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// ============================================================================
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// [Forward Declarations]
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// ============================================================================
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class BaseEmitter;
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// ============================================================================
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// [asmjit::ErrorHandler]
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// ============================================================================
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//! Error handler can be used to override the default behavior of error handling.
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//!
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//! It's available to all classes that inherit `BaseEmitter`. Override
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//! \ref ErrorHandler::handleError() to implement your own error handler.
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//!
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//! The following use-cases are supported:
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//!
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//! - Record the error and continue code generation. This is the simplest
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//! approach that can be used to at least log possible errors.
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//! - Throw an exception. AsmJit doesn't use exceptions and is completely
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//! exception-safe, but it's perfectly legal to throw an exception from
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//! the error handler.
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//! - Use plain old C's `setjmp()` and `longjmp()`. Asmjit always puts Assembler,
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//! Builder and Compiler to a consistent state before calling \ref handleError(),
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//! so `longjmp()` can be used without issues to cancel the code-generation if
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//! an error occurred. This method can be used if exception handling in your
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//! project is turned off and you still want some comfort. In most cases it
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//! should be safe as AsmJit uses \ref Zone memory and the ownership of memory
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//! it allocates always ends with the instance that allocated it. If using this
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//! approach please never jump outside the life-time of \ref CodeHolder and
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//! \ref BaseEmitter.
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//!
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//! \ref ErrorHandler can be attached to \ref CodeHolder or \ref BaseEmitter,
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//! which has a priority. The example below uses error handler that just prints
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//! the error, but lets AsmJit continue:
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//!
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//! ```
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//! // Error Handling #1 - Logging and returing Error.
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//! #include <asmjit/x86.h>
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//! #include <stdio.h>
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//!
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//! using namespace asmjit;
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//!
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//! // Error handler that just prints the error and lets AsmJit ignore it.
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//! class SimpleErrorHandler : public ErrorHandler {
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//! public:
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//! Error err;
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//!
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//! inline SimpleErrorHandler() : err(kErrorOk) {}
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//!
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//! void handleError(Error err, const char* message, BaseEmitter* origin) override {
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//! this->err = err;
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//! fprintf(stderr, "ERROR: %s\n", message);
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//! }
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//! };
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//!
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//! int main() {
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//! JitRuntime rt;
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//! SimpleErrorHandler eh;
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//!
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//! CodeHolder code;
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//! code.init(rt.environment());
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//! code.setErrorHandler(&eh);
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//!
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//! // Try to emit instruction that doesn't exist.
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//! x86::Assembler a(&code);
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//! a.emit(x86::Inst::kIdMov, x86::xmm0, x86::xmm1);
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//!
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//! if (eh.err) {
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//! // Assembler failed!
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//! return 1;
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//! }
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//!
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//! return 0;
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//! }
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//! ```
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//!
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//! If error happens during instruction emitting / encoding the assembler behaves
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//! transactionally - the output buffer won't advance if encoding failed, thus
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//! either a fully encoded instruction or nothing is emitted. The error handling
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//! shown above is useful, but it's still not the best way of dealing with errors
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//! in AsmJit. The following example shows how to use exception handling to handle
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//! errors in a more C++ way:
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//!
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//! ```
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//! // Error Handling #2 - Throwing an exception.
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//! #include <asmjit/x86.h>
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//! #include <exception>
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//! #include <string>
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//! #include <stdio.h>
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//!
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//! using namespace asmjit;
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//!
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//! // Error handler that throws a user-defined `AsmJitException`.
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//! class AsmJitException : public std::exception {
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//! public:
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//! Error err;
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//! std::string message;
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//!
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//! AsmJitException(Error err, const char* message) noexcept
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//! : err(err),
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//! message(message) {}
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//!
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//! const char* what() const noexcept override { return message.c_str(); }
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//! };
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//!
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//! class ThrowableErrorHandler : public ErrorHandler {
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//! public:
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//! // Throw is possible, functions that use ErrorHandler are never 'noexcept'.
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//! void handleError(Error err, const char* message, BaseEmitter* origin) override {
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//! throw AsmJitException(err, message);
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//! }
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//! };
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//!
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//! int main() {
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//! JitRuntime rt;
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//! ThrowableErrorHandler eh;
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//!
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//! CodeHolder code;
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//! code.init(rt.environment());
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//! code.setErrorHandler(&eh);
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//!
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//! x86::Assembler a(&code);
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//!
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//! // Try to emit instruction that doesn't exist.
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//! try {
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//! a.emit(x86::Inst::kIdMov, x86::xmm0, x86::xmm1);
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//! }
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//! catch (const AsmJitException& ex) {
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//! printf("EXCEPTION THROWN: %s\n", ex.what());
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//! return 1;
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//! }
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//!
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//! return 0;
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//! }
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//! ```
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//!
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//! If C++ exceptions are not what you like or your project turns off them
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//! completely there is still a way of reducing the error handling to a minimum
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//! by using a standard setjmp/longjmp approach. AsmJit is exception-safe and
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//! cleans up everything before calling the ErrorHandler, so any approach is
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//! safe. You can simply jump from the error handler without causing any
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//! side-effects or memory leaks. The following example demonstrates how it
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//! could be done:
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//!
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//! ```
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//! // Error Handling #3 - Using setjmp/longjmp if exceptions are not allowed.
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//! #include <asmjit/x86.h>
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//! #include <setjmp.h>
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//! #include <stdio.h>
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//!
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//! class LongJmpErrorHandler : public asmjit::ErrorHandler {
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//! public:
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//! inline LongJmpErrorHandler() : err(asmjit::kErrorOk) {}
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//!
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//! void handleError(asmjit::Error err, const char* message, asmjit::BaseEmitter* origin) override {
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//! this->err = err;
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//! longjmp(state, 1);
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//! }
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//!
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//! jmp_buf state;
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//! asmjit::Error err;
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//! };
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//!
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//! int main(int argc, char* argv[]) {
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//! using namespace asmjit;
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//!
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//! JitRuntime rt;
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//! LongJmpErrorHandler eh;
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//!
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//! CodeHolder code;
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//! code.init(rt.rt.environment());
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//! code.setErrorHandler(&eh);
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//!
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//! x86::Assembler a(&code);
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//!
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//! if (!setjmp(eh.state)) {
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//! // Try to emit instruction that doesn't exist.
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//! a.emit(x86::Inst::kIdMov, x86::xmm0, x86::xmm1);
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//! }
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//! else {
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//! Error err = eh.err;
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//! printf("ASMJIT ERROR: 0x%08X [%s]\n", err, DebugUtils::errorAsString(err));
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//! }
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//!
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//! return 0;
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//! }
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//! ```
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class ASMJIT_VIRTAPI ErrorHandler {
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public:
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ASMJIT_BASE_CLASS(ErrorHandler)
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// --------------------------------------------------------------------------
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// [Construction / Destruction]
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// --------------------------------------------------------------------------
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//! Creates a new `ErrorHandler` instance.
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ASMJIT_API ErrorHandler() noexcept;
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//! Destroys the `ErrorHandler` instance.
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ASMJIT_API virtual ~ErrorHandler() noexcept;
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// --------------------------------------------------------------------------
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// [Handle Error]
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// --------------------------------------------------------------------------
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//! Error handler (must be reimplemented).
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//!
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//! Error handler is called after an error happened and before it's propagated
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//! to the caller. There are multiple ways how the error handler can be used:
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//!
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//! 1. User-based error handling without throwing exception or using C's
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//! `longjmp()`. This is for users that don't use exceptions and want
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//! customized error handling.
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//!
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//! 2. Throwing an exception. AsmJit doesn't use exceptions and is completely
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//! exception-safe, but you can throw exception from your error handler if
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//! this way is the preferred way of handling errors in your project.
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//!
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//! 3. Using plain old C's `setjmp()` and `longjmp()`. Asmjit always puts
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//! `BaseEmitter` to a consistent state before calling `handleError()`
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//! so `longjmp()` can be used without any issues to cancel the code
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//! generation if an error occurred. There is no difference between
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//! exceptions and `longjmp()` from AsmJit's perspective, however,
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//! never jump outside of `CodeHolder` and `BaseEmitter` scope as you
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//! would leak memory.
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virtual void handleError(Error err, const char* message, BaseEmitter* origin) = 0;
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};
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//! \}
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ASMJIT_END_NAMESPACE
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#endif // ASMJIT_CORE_ERRORHANDLER_H_INCLUDED
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