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39
40#ifndef QV4_ALLOCA_H
41#define QV4_ALLOCA_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#include <QtCore/private/qglobal_p.h>
55
56#if QT_CONFIG(alloca_h)
57# include <alloca.h>
58#elif QT_CONFIG(alloca_malloc_h)
59# include <malloc.h>
60// This does not matter unless compiling in strict standard mode.
61# ifdef Q_CC_MSVC
62# define alloca _alloca
63# endif
64#else
65# include <stdlib.h>
66#endif
67
68// Define Q_ALLOCA_VAR macro to be used instead of #ifdeffing
69// the occurrences of alloca() in case it's not supported.
70// Q_ALLOCA_DECLARE and Q_ALLOCA_ASSIGN macros separate
71// memory allocation from the declaration and RAII.
72#define Q_ALLOCA_VAR(type, name, size) \
73 Q_ALLOCA_DECLARE(type, name); \
74 Q_ALLOCA_ASSIGN(type, name, size)
75
76#if QT_CONFIG(alloca)
77
78#define Q_ALLOCA_DECLARE(type, name) \
79 type *name = 0
80
81#define Q_ALLOCA_ASSIGN(type, name, size) \
82 name = static_cast<type*>(alloca(size))
83
84#else
85QT_BEGIN_NAMESPACE
86class Qt_AllocaWrapper
87{
88public:
89 Qt_AllocaWrapper() { m_data = 0; }
90 ~Qt_AllocaWrapper() { free(m_data); }
91 void *data() { return m_data; }
92 void allocate(int size) { m_data = malloc(size); memset(m_data, 0, size); }
93private:
94 void *m_data;
95};
96QT_END_NAMESPACE
97
98#define Q_ALLOCA_DECLARE(type, name) \
99 Qt_AllocaWrapper _qt_alloca_##name; \
100 type *name = nullptr
101
102#define Q_ALLOCA_ASSIGN(type, name, size) \
103 _qt_alloca_##name.allocate(size); \
104 name = static_cast<type*>(_qt_alloca_##name.data())
105
106#endif
107
108#endif
109

source code of qtdeclarative/src/qml/common/qv4alloca_p.h