1//===- ErrorHandler.h -------------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// We designed lld's error handlers with the following goals in mind:
10//
11// - Errors can occur at any place where we handle user input, but we don't
12// want them to affect the normal execution path too much. Ideally,
13// handling errors should be as simple as reporting them and exit (but
14// without actually doing exit).
15//
16// In particular, the design to wrap all functions that could fail with
17// ErrorOr<T> is rejected because otherwise we would have to wrap a large
18// number of functions in lld with ErrorOr. With that approach, if some
19// function F can fail, not only F but all functions that transitively call
20// F have to be wrapped with ErrorOr. That seemed too much.
21//
22// - Finding only one error at a time is not sufficient. We want to find as
23// many errors as possible with one execution of the linker. That means the
24// linker needs to keep running after a first error and give up at some
25// checkpoint (beyond which it would find cascading, false errors caused by
26// the previous errors).
27//
28// - We want a simple interface to report errors. Unlike Clang, the data we
29// handle is compiled binary, so we don't need an error reporting mechanism
30// that's as sophisticated as the one that Clang has.
31//
32// The current lld's error handling mechanism is simple:
33//
34// - When you find an error, report it using error() and continue as far as
35// you can. An internal error counter is incremented by one every time you
36// call error().
37//
38// A common idiom to handle an error is calling error() and then returning
39// a reasonable default value. For example, if your function handles a
40// user-supplied alignment value, and if you find an invalid alignment
41// (e.g. 17 which is not 2^n), you may report it using error() and continue
42// as if it were alignment 1 (which is the simplest reasonable value).
43//
44// Note that you should not continue with an invalid value; that breaks the
45// internal consistency. You need to maintain all variables have some sane
46// value even after an error occurred. So, when you have to continue with
47// some value, always use a dummy value.
48//
49// - Find a reasonable checkpoint at where you want to stop the linker, and
50// add code to return from the function if errorCount() > 0. In most cases,
51// a checkpoint already exists, so you don't need to do anything for this.
52//
53// This interface satisfies all the goals that we mentioned above.
54//
55// You should never call fatal() except for reporting a corrupted input file.
56// fatal() immediately terminates the linker, so the function is not desirable
57// if you are using lld as a subroutine in other program, and with that you
58// can find only one error at a time.
59//
60// warn() doesn't do anything but printing out a given message.
61//
62// It is not recommended to use llvm::outs() or lld::errs() directly in lld
63// because they are not thread-safe. The functions declared in this file are
64// thread-safe.
65//
66//===----------------------------------------------------------------------===//
67
68#ifndef LLD_COMMON_ERRORHANDLER_H
69#define LLD_COMMON_ERRORHANDLER_H
70
71#include "lld/Common/LLVM.h"
72
73#include "llvm/ADT/STLExtras.h"
74#include "llvm/Support/Error.h"
75#include "llvm/Support/FileOutputBuffer.h"
76
77namespace llvm {
78class DiagnosticInfo;
79class raw_ostream;
80}
81
82namespace lld {
83
84// We wrap stdout and stderr so that you can pass alternative stdout/stderr as
85// arguments to lld::*::link() functions.
86extern llvm::raw_ostream *stdoutOS;
87extern llvm::raw_ostream *stderrOS;
88
89llvm::raw_ostream &outs();
90llvm::raw_ostream &errs();
91
92enum class ErrorTag { LibNotFound, SymbolNotFound };
93
94class ErrorHandler {
95public:
96 uint64_t errorCount = 0;
97 uint64_t errorLimit = 20;
98 StringRef errorLimitExceededMsg = "too many errors emitted, stopping now";
99 StringRef errorHandlingScript;
100 StringRef logName = "lld";
101 bool exitEarly = true;
102 bool fatalWarnings = false;
103 bool verbose = false;
104 bool vsDiagnostics = false;
105 bool disableOutput = false;
106 std::function<void()> cleanupCallback;
107
108 void error(const Twine &msg);
109 void error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args);
110 LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &msg);
111 void log(const Twine &msg);
112 void message(const Twine &msg);
113 void warn(const Twine &msg);
114
115 void reset() {
116 if (cleanupCallback)
117 cleanupCallback();
118 *this = ErrorHandler();
119 }
120
121 std::unique_ptr<llvm::FileOutputBuffer> outputBuffer;
122
123private:
124 using Colors = raw_ostream::Colors;
125
126 std::string getLocation(const Twine &msg);
127};
128
129/// Returns the default error handler.
130ErrorHandler &errorHandler();
131
132inline void error(const Twine &msg) { errorHandler().error(msg); }
133inline void error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args) {
134 errorHandler().error(msg, tag, args);
135}
136inline LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &msg) {
137 errorHandler().fatal(msg);
138}
139inline void log(const Twine &msg) { errorHandler().log(msg); }
140inline void message(const Twine &msg) { errorHandler().message(msg); }
141inline void warn(const Twine &msg) { errorHandler().warn(msg); }
142inline uint64_t errorCount() { return errorHandler().errorCount; }
143
144LLVM_ATTRIBUTE_NORETURN void exitLld(int val);
145
146void diagnosticHandler(const llvm::DiagnosticInfo &di);
147void checkError(Error e);
148
149// check functions are convenient functions to strip errors
150// from error-or-value objects.
151template <class T> T check(ErrorOr<T> e) {
152 if (auto ec = e.getError())
153 fatal(ec.message());
154 return std::move(*e);
155}
156
157template <class T> T check(Expected<T> e) {
158 if (!e)
159 fatal(llvm::toString(e.takeError()));
160 return std::move(*e);
161}
162
163// Don't move from Expected wrappers around references.
164template <class T> T &check(Expected<T &> e) {
165 if (!e)
166 fatal(llvm::toString(e.takeError()));
167 return *e;
168}
169
170template <class T>
171T check2(ErrorOr<T> e, llvm::function_ref<std::string()> prefix) {
172 if (auto ec = e.getError())
173 fatal(prefix() + ": " + ec.message());
174 return std::move(*e);
175}
176
177template <class T>
178T check2(Expected<T> e, llvm::function_ref<std::string()> prefix) {
179 if (!e)
180 fatal(prefix() + ": " + toString(e.takeError()));
181 return std::move(*e);
182}
183
184inline std::string toString(const Twine &s) { return s.str(); }
185
186// To evaluate the second argument lazily, we use C macro.
187#define CHECK(E, S) check2((E), [&] { return toString(S); })
188
189} // namespace lld
190
191#endif
192