1// Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, [email protected], author Rafael Roquetto <[email protected]>
2// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
3
4#ifndef QTRACE_P_H
5#define QTRACE_P_H
6
7//
8// W A R N I N G
9// -------------
10//
11// This file is not part of the Qt API. It exists purely as an
12// implementation detail. This header file may change from version to
13// version without notice, or even be removed.
14//
15// We mean it.
16//
17
18/*
19 * The Qt tracepoints API consists of only five macros:
20 *
21 * - Q_TRACE(tracepoint, args...)
22 * Fires 'tracepoint' if it is enabled.
23 *
24 * - Q_TRACE_EXIT(tracepoint, args...)
25 * Fires 'tracepoint' if it is enabled when the current scope exists.
26 *
27 * - Q_TRACE_SCOPE(tracepoint, args...)
28 * Wrapper around Q_TRACE/_EXIT to trace entry and exit. First it traces
29 * `${tracepoint}_entry` and then `${tracepoint}_exit` on scope exit.
30 *
31 * - Q_UNCONDITIONAL_TRACE(tracepoint, args...)
32 * Fires 'tracepoint' unconditionally: no check is performed to query
33 * whether 'tracepoint' is enabled.
34 *
35 * - Q_TRACE_ENABLED(tracepoint)
36 * Returns 'true' if 'tracepoint' is enabled; false otherwise.
37 *
38 * When using LTTNG, Q_TRACE, Q_UNCONDITIONAL_TRACE and Q_TRACE_ENABLED map
39 * ultimately to tracepoint(), do_tracepoint() and tracepoint_enabled(),
40 * respectively, described on the lttng-ust manpage (man 3 lttng-ust).
41 *
42 * On ETW, Q_TRACE() and Q_UNCONDITIONAL_TRACE() are equivalent, ultimately
43 * amounting to a call to TraceLoggingWrite(), whereas Q_TRACE_ENABLED()
44 * wraps around TraceLoggingProviderEnabled().
45 *
46 * A tracepoint provider is defined in a separate file, that follows the
47 * following format:
48 *
49 * tracepoint_name(arg_type arg_name, ...)
50 *
51 * For instance:
52 *
53 * qcoreapplication_ctor(int argc, const char * const argv)
54 * qcoreapplication_foo(int argc, const char[10] argv)
55 * qcoreapplication_baz(const char[len] some_string, unsigned int len)
56 * qcoreapplication_qstring(const QString &foo)
57 * qcoreapplication_qrect(const QRect &rect)
58 *
59 * The provider file is then parsed by src/tools/tracegen, which can be
60 * switched to output either ETW, CTF or LTTNG tracepoint definitions. The provider
61 * name is deduced to be basename(provider_file).
62 *
63 * To use the above (inside qtcore), you need to include
64 * <providername_tracepoints_p.h>. After that, the following call becomes
65 * possible:
66 *
67 * Q_TRACE(qcoreapplication_qrect, myRect);
68 *
69 * Currently, all C++ primitive non-pointer types are supported for
70 * arguments. Additionally, char * is supported, and is assumed to
71 * be a NULL-terminated string. Finally, the following subset of Qt types also
72 * currently supported:
73 *
74 * - QString
75 * - QByteArray
76 * - QUrl
77 * - QRect
78 * - QRectF
79 * - QSize
80 * - QSizeF
81 *
82 * Dynamic arrays are supported using the syntax illustrated by
83 * qcoreapplication_baz above.
84 *
85 * One can also add prefix for the generated providername_tracepoints_p.h file
86 * by specifying it inside brackets '{ }' in the tracepoints file. One can
87 * for example add forward declaration for a type:
88 *
89 * {
90 * QT_BEGIN_NAMESPACE
91 * class QEvent;
92 * QT_END_NAMESPACE
93 * }
94 *
95 * Metadata
96 *
97 * Metadata is used to add textual information for different types such
98 * as enums and flags. How this data is handled depends on the used backend.
99 * For ETW, the values are converted to text, for CTF and LTTNG they are used to add
100 * CTF enumerations, which are converted to text after tracing.
101 *
102 * Enumererations are specified using ENUM:
103 *
104 * ENUM {
105 * Enum0 = 0,
106 * Enum1 = 1,
107 * Enum2,
108 * RANGE(RangeEnum, 3 ... 10),
109 * } Name;
110 *
111 * Name must match to one of the enumerations used in the tracepoints. Range of values
112 * can be provided using RANGE(name, first ... last). All values must be unique.
113 *
114 * Flags are specified using FLAGS:
115 *
116 * FLAGS {
117 * Default = 0,
118 * Flag0 = 1,
119 * Flag1 = 2,
120 * Flag2 = 4,
121 * } Name;
122 *
123 * Name must match to one of the flags used in the tracepoints. Each value must be
124 * power of two and unique.
125 */
126
127#include <QtCore/private/qglobal_p.h>
128#include <QtCore/qscopeguard.h>
129
130QT_BEGIN_NAMESPACE
131
132#if defined(Q_TRACEPOINT) && !defined(QT_BOOTSTRAPPED)
133# define Q_HAS_TRACEPOINTS 1
134# define Q_TRACE(x, ...) QtPrivate::trace_ ## x(__VA_ARGS__)
135# define Q_TRACE_EXIT(x, ...) \
136 const auto qTraceExit_ ## x ## __COUNTER__ = qScopeGuard([&]() { Q_TRACE(x, __VA_ARGS__); });
137# define Q_TRACE_SCOPE(x, ...) \
138 Q_TRACE(x ## _entry, __VA_ARGS__); \
139 Q_TRACE_EXIT(x ## _exit);
140# define Q_UNCONDITIONAL_TRACE(x, ...) QtPrivate::do_trace_ ## x(__VA_ARGS__)
141# define Q_TRACE_ENABLED(x) QtPrivate::trace_ ## x ## _enabled()
142#else
143# define Q_HAS_TRACEPOINTS 0
144# define Q_TRACE(x, ...)
145# define Q_TRACE_EXIT(x, ...)
146# define Q_TRACE_SCOPE(x, ...)
147# define Q_UNCONDITIONAL_TRACE(x, ...)
148# define Q_TRACE_ENABLED(x) false
149#endif // defined(Q_TRACEPOINT) && !defined(QT_BOOTSTRAPPED)
150
151
152/*
153 * The Qt tracepoints can also be defined directly in the source files using
154 * the following macros. If using these macros, the tracepoints file is automatically
155 * generated using the tracepointgen tool. The tool scans the input files for
156 * these macros. These macros are ignored during compile time. Both automatic
157 * generation and manually specifying tracepoints in a file can't be done at the same
158 * time for the same provider.
159 *
160 * - Q_TRACE_INSTRUMENT(provider)
161 * Generate entry/exit tracepoints for a function. For example, member function
162 *
163 * void SomeClass::method(int param1, float param2)
164 * {
165 * ...
166 * }
167 *
168 * converted to use tracepoints:
169 *
170 * void Q_TRACE_INSTRUMENT(provider) SomeClass::method(int param1, float param2)
171 * {
172 * Q_TRACE_SCOPE(SomeClass_method, param1, param2);
173 * ...
174 * }
175 *
176 * generates following tracepoints in provider.tracepoints file:
177 *
178 * SomeClass_method_entry(int param1, float param2)
179 * SomeClass_method_exit()
180 *
181 * - Q_TRACE_PARAM_REPLACE(in, out)
182 * Can be used with Q_TRACE_INSTRUMENT to replace parameter type in with type out.
183 * If a parameter type is not supported by the tracegen tool, one can use this to
184 * change it to another supported type.
185 *
186 * void Q_TRACE_INSTRUMENT(provider) SomeClass::method(int param1, UserType param2)
187 * {
188 * Q_TRACE_PARAM_REPLACE(UserType, QString);
189 * Q_TRACE_SCOPE(SomeClass_method, param1, param2.toQString());
190 * }
191 *
192 * - Q_TRACE_POINT(provider, tracepoint, ...)
193 * Manually specify tracepoint for the provider. 'tracepoint' is the full name
194 * of the tracepoint and ... can be zero or more parameters.
195 *
196 * Q_TRACE_POINT(provider, SomeClass_function_entry, int param1, int param2);
197 *
198 * generates following tracepoint:
199 *
200 * SomeClass_function_entry(int param1, int param2)
201 *
202 * - Q_TRACE_PREFIX(provider, prefix)
203 * Provide prefix for the tracepoint. Multiple prefixes can be specified for the same
204 * provider in different files, they are all concatenated into one in the
205 * provider.tracepoints file.
206 *
207 * Q_TRACE_PREFIX(provider,
208 * "QT_BEGIN_NAMESPACE" \
209 * "class QEvent;" \
210 * "QT_END_NAMESPACE")
211 *
212 * - Q_TRACE_METADATA(provider, metadata)
213 * Provides metadata for the tracepoint provider.
214 *
215 * Q_TRACE_METADATA(qtgui,
216 * "ENUM {" \
217 * "Format_Invalid," \
218 * "Format_Mono," \
219 * "Format_MonoLSB," \
220 * "Format_Indexed8," \
221 * ...
222 * "} QImage::Format;" \
223 * );
224 *
225 * If the content of enum is empty or contains keyword AUTO, then the tracepointgen tool
226 * tries to find the enumeration from header files.
227 *
228 * Q_TRACE_METADATA(qtcore, "ENUM { AUTO, RANGE User ... MaxUser } QEvent::Type;");
229 */
230#define Q_TRACE_INSTRUMENT(provider)
231#define Q_TRACE_PARAM_REPLACE(in, out)
232#define Q_TRACE_POINT(provider, tracepoint, ...)
233#define Q_TRACE_PREFIX(provider, prefix)
234#define Q_TRACE_METADATA(provider, metadata)
235
236QT_END_NAMESPACE
237
238#endif // QTRACE_P_H
239

source code of qtbase/src/corelib/global/qtrace_p.h