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39
40#include "qplatformdefs.h"
41
42#include <stdlib.h>
43#include <string.h>
44
45/*
46 Define the container allocation functions in a separate file, so that our
47 users can easily override them.
48*/
49
50QT_BEGIN_NAMESPACE
51
52#if !QT_DEPRECATED_SINCE(5, 0)
53// Make sure they're defined to be exported
54Q_CORE_EXPORT void *qMalloc(size_t size) Q_ALLOC_SIZE(1);
55Q_CORE_EXPORT void qFree(void *ptr);
56Q_CORE_EXPORT void *qRealloc(void *ptr, size_t size) Q_ALLOC_SIZE(2);
57#endif
58
59
60void *qMalloc(size_t size)
61{
62 return ::malloc(size: size);
63}
64
65void qFree(void *ptr)
66{
67 ::free(ptr: ptr);
68}
69
70void *qRealloc(void *ptr, size_t size)
71{
72 return ::realloc(ptr: ptr, size: size);
73}
74
75void *qMallocAligned(size_t size, size_t alignment)
76{
77 return qReallocAligned(ptr: nullptr, size, oldsize: 0, alignment);
78}
79
80void *qReallocAligned(void *oldptr, size_t newsize, size_t oldsize, size_t alignment)
81{
82 // fake an aligned allocation
83 void *actualptr = oldptr ? static_cast<void **>(oldptr)[-1] : nullptr;
84 if (alignment <= sizeof(void*)) {
85 // special, fast case
86 void **newptr = static_cast<void **>(realloc(ptr: actualptr, size: newsize + sizeof(void*)));
87 if (!newptr)
88 return nullptr;
89 if (newptr == actualptr) {
90 // realloc succeeded without reallocating
91 return oldptr;
92 }
93
94 *newptr = newptr;
95 return newptr + 1;
96 }
97
98 // malloc returns pointers aligned at least at sizeof(size_t) boundaries
99 // but usually more (8- or 16-byte boundaries).
100 // So we overallocate by alignment-sizeof(size_t) bytes, so we're guaranteed to find a
101 // somewhere within the first alignment-sizeof(size_t) that is properly aligned.
102
103 // However, we need to store the actual pointer, so we need to allocate actually size +
104 // alignment anyway.
105
106 void *real = realloc(ptr: actualptr, size: newsize + alignment);
107 if (!real)
108 return nullptr;
109
110 quintptr faked = reinterpret_cast<quintptr>(real) + alignment;
111 faked &= ~(alignment - 1);
112 void **faked_ptr = reinterpret_cast<void **>(faked);
113
114 if (oldptr) {
115 qptrdiff oldoffset = static_cast<char *>(oldptr) - static_cast<char *>(actualptr);
116 qptrdiff newoffset = reinterpret_cast<char *>(faked_ptr) - static_cast<char *>(real);
117 if (oldoffset != newoffset)
118 memmove(dest: faked_ptr, src: static_cast<char *>(real) + oldoffset, n: qMin(a: oldsize, b: newsize));
119 }
120
121 // now save the value of the real pointer at faked-sizeof(void*)
122 // by construction, alignment > sizeof(void*) and is a power of 2, so
123 // faked-sizeof(void*) is properly aligned for a pointer
124 faked_ptr[-1] = real;
125
126 return faked_ptr;
127}
128
129void qFreeAligned(void *ptr)
130{
131 if (!ptr)
132 return;
133 void **ptr2 = static_cast<void **>(ptr);
134 free(ptr: ptr2[-1]);
135}
136
137QT_END_NAMESPACE
138
139

source code of qtbase/src/corelib/global/qmalloc.cpp