1/****************************************************************************
2**
3** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Rafael Roquetto <rafael.roquetto@kdab.com>
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39
40#ifndef QTRACE_P_H
41#define QTRACE_P_H
42
43//
44// W A R N I N G
45// -------------
46//
47// This file is not part of the Qt API. It exists purely as an
48// implementation detail. This header file may change from version to
49// version without notice, or even be removed.
50//
51// We mean it.
52//
53
54/*
55 * The Qt tracepoints API consists of only five macros:
56 *
57 * - Q_TRACE(tracepoint, args...)
58 * Fires 'tracepoint' if it is enabled.
59 *
60 * - Q_TRACE_EXIT(tracepoint, args...)
61 * Fires 'tracepoint' if it is enabled when the current scope exists.
62 *
63 * - Q_TRACE_SCOPE(tracepoint, args...)
64 * Wrapper around Q_TRACE/_EXIT to trace entry and exit. First it traces
65 * `${tracepoint}_entry` and then `${tracepoint}_exit` on scope exit.
66 *
67 * - Q_UNCONDITIONAL_TRACE(tracepoint, args...)
68 * Fires 'tracepoint' unconditionally: no check is performed to query
69 * whether 'tracepoint' is enabled.
70 *
71 * - Q_TRACE_ENABLED(tracepoint)
72 * Returns 'true' if 'tracepoint' is enabled; false otherwise.
73 *
74 * When using LTTNG, Q_TRACE, Q_UNCONDITIONAL_TRACE and Q_TRACE_ENABLED map
75 * ultimately to tracepoint(), do_tracepoint() and tracepoint_enabled(),
76 * respectively, described on the lttng-ust manpage (man 3 lttng-ust).
77 *
78 * On ETW, Q_TRACE() and Q_UNCONDITIONAL_TRACE() are equivalent, ultimately
79 * amounting to a call to TraceLoggingWrite(), whereas Q_TRACE_ENABLED()
80 * wraps around TraceLoggingProviderEnabled().
81 *
82 * A tracepoint provider is defined in a separate file, that follows the
83 * following format:
84 *
85 * tracepoint_name(arg_type arg_name, ...)
86 *
87 * For instance:
88 *
89 * qcoreapplication_ctor(int argc, const char * const argv)
90 * qcoreapplication_foo(int argc, const char[10] argv)
91 * qcoreapplication_baz(const char[len] some_string, unsigned int len)
92 * qcoreapplication_qstring(const QString &foo)
93 * qcoreapplication_qrect(const QRect &rect)
94 *
95 * The provider file is then parsed by src/tools/tracegen, which can be
96 * switched to output either ETW or LTTNG tracepoint definitions. The provider
97 * name is deduced to be basename(provider_file).
98 *
99 * To use the above (inside qtcore), you need to include
100 * <providername_tracepoints_p.h>. After that, the following call becomes
101 * possible:
102 *
103 * Q_TRACE(qcoreapplication_qrect, myRect);
104 *
105 * Currently, all C++ primitive non-pointer types are supported for
106 * arguments. Additionally, char * is supported, and is assumed to
107 * be a NULL-terminated string. Finally, the following subset of Qt types also
108 * currently supported:
109 *
110 * - QString
111 * - QByteArray
112 * - QUrl
113 * - QRect
114 *
115 * Dynamic arrays are supported using the syntax illustrated by
116 * qcoreapplication_baz above.
117 */
118
119#include <QtCore/qglobal.h>
120#include <QtCore/qscopeguard.h>
121
122QT_BEGIN_NAMESPACE
123
124#if defined(Q_TRACEPOINT) && !defined(QT_BOOTSTRAPPED)
125# define Q_HAS_TRACEPOINTS 1
126# define Q_TRACE(x, ...) QtPrivate::trace_ ## x(__VA_ARGS__)
127# define Q_TRACE_EXIT(x, ...) \
128 const auto qTraceExit_ ## x ## __COUNTER__ = qScopeGuard([&]() { Q_TRACE(x, __VA_ARGS__); });
129# define Q_TRACE_SCOPE(x, ...) \
130 Q_TRACE(x ## _entry, __VA_ARGS__); \
131 Q_TRACE_EXIT(x ## _exit);
132# define Q_UNCONDITIONAL_TRACE(x, ...) QtPrivate::do_trace_ ## x(__VA_ARGS__)
133# define Q_TRACE_ENABLED(x) QtPrivate::trace_ ## x ## _enabled()
134#else
135# define Q_HAS_TRACEPOINTS 0
136# define Q_TRACE(x, ...)
137# define Q_TRACE_EXIT(x, ...)
138# define Q_TRACE_SCOPE(x, ...)
139# define Q_UNCONDITIONAL_TRACE(x, ...)
140# define Q_TRACE_ENABLED(x) false
141#endif // defined(Q_TRACEPOINT) && !defined(QT_BOOTSTRAPPED)
142
143QT_END_NAMESPACE
144
145#endif // QTRACE_P_H
146