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
77 namespace llvm {
78 class DiagnosticInfo;
79 class raw_ostream;
80 }
81
82 namespace lld {
83
84 // We wrap stdout and stderr so that you can pass alternative stdout/stderr as
85 // arguments to lld::*::link() functions.
86 extern llvm::raw_ostream *stdoutOS;
87 extern llvm::raw_ostream *stderrOS;
88
89 llvm::raw_ostream &outs();
90 llvm::raw_ostream &errs();
91
92 enum class ErrorTag { LibNotFound, SymbolNotFound };
93
94 class ErrorHandler {
95 public:
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
reset()115 void reset() {
116 if (cleanupCallback)
117 cleanupCallback();
118 *this = ErrorHandler();
119 }
120
121 std::unique_ptr<llvm::FileOutputBuffer> outputBuffer;
122
123 private:
124 using Colors = raw_ostream::Colors;
125
126 std::string getLocation(const Twine &msg);
127 };
128
129 /// Returns the default error handler.
130 ErrorHandler &errorHandler();
131
error(const Twine & msg)132 inline void error(const Twine &msg) { errorHandler().error(msg); }
error(const Twine & msg,ErrorTag tag,ArrayRef<StringRef> args)133 inline void error(const Twine &msg, ErrorTag tag, ArrayRef<StringRef> args) {
134 errorHandler().error(msg, tag, args);
135 }
fatal(const Twine & msg)136 inline LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &msg) {
137 errorHandler().fatal(msg);
138 }
log(const Twine & msg)139 inline void log(const Twine &msg) { errorHandler().log(msg); }
message(const Twine & msg)140 inline void message(const Twine &msg) { errorHandler().message(msg); }
warn(const Twine & msg)141 inline void warn(const Twine &msg) { errorHandler().warn(msg); }
errorCount()142 inline uint64_t errorCount() { return errorHandler().errorCount; }
143
144 LLVM_ATTRIBUTE_NORETURN void exitLld(int val);
145
146 void diagnosticHandler(const llvm::DiagnosticInfo &di);
147 void checkError(Error e);
148
149 // check functions are convenient functions to strip errors
150 // from error-or-value objects.
check(ErrorOr<T> e)151 template <class T> T check(ErrorOr<T> e) {
152 if (auto ec = e.getError())
153 fatal(ec.message());
154 return std::move(*e);
155 }
156
check(Expected<T> e)157 template <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.
check(Expected<T &> e)164 template <class T> T &check(Expected<T &> e) {
165 if (!e)
166 fatal(llvm::toString(e.takeError()));
167 return *e;
168 }
169
170 template <class T>
check2(ErrorOr<T> e,llvm::function_ref<std::string ()> prefix)171 T 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
177 template <class T>
check2(Expected<T> e,llvm::function_ref<std::string ()> prefix)178 T 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
toString(const Twine & s)184 inline 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