swr: fix build with mingw
[mesa.git] / src / gallium / README.portability
1 CROSS-PLATFORM PORTABILITY GUIDELINES FOR GALLIUM3D
2
3
4 = General Considerations =
5
6 The frontend and winsys driver support a rather limited number of
7 platforms. However, the pipe drivers are meant to run in a wide number of
8 platforms. Hence the pipe drivers, the auxiliary modules, and all public
9 headers in general, should strictly follow these guidelines to ensure
10
11
12 = Compiler Support =
13
14 * Include the p_compiler.h.
15
16 * Cast explicitly when converting to integer types of smaller sizes.
17
18 * Cast explicitly when converting between float, double and integral types.
19
20 * Don't use named struct initializers.
21
22 * Don't use variable number of macro arguments. Use static inline functions
23 instead.
24
25 * Don't use C99 features.
26
27 = Standard Library =
28
29 * Avoid including standard library headers. Most standard library functions are
30 not available in Windows Kernel Mode. Use the appropriate p_*.h include.
31
32 == Memory Allocation ==
33
34 * Use MALLOC, CALLOC, FREE instead of the malloc, calloc, free functions.
35
36 * Use align_pointer() function defined in u_memory.h for aligning pointers
37 in a portable way.
38
39 == Debugging ==
40
41 * Use the functions/macros in p_debug.h.
42
43 * Don't include assert.h, call abort, printf, etc.
44
45
46 = Code Style =
47
48 == Inherantice in C ==
49
50 The main thing we do is mimic inheritance by structure containment.
51
52 Here's a silly made-up example:
53
54 /* base class */
55 struct buffer
56 {
57 int size;
58 void (*validate)(struct buffer *buf);
59 };
60
61 /* sub-class of bufffer */
62 struct texture_buffer
63 {
64 struct buffer base; /* the base class, MUST COME FIRST! */
65 int format;
66 int width, height;
67 };
68
69
70 Then, we'll typically have cast-wrapper functions to convert base-class
71 pointers to sub-class pointers where needed:
72
73 static inline struct vertex_buffer *vertex_buffer(struct buffer *buf)
74 {
75 return (struct vertex_buffer *) buf;
76 }
77
78
79 To create/init a sub-classed object:
80
81 struct buffer *create_texture_buffer(int w, int h, int format)
82 {
83 struct texture_buffer *t = malloc(sizeof(*t));
84 t->format = format;
85 t->width = w;
86 t->height = h;
87 t->base.size = w * h;
88 t->base.validate = tex_validate;
89 return &t->base;
90 }
91
92 Example sub-class method:
93
94 void tex_validate(struct buffer *buf)
95 {
96 struct texture_buffer *tb = texture_buffer(buf);
97 assert(tb->format);
98 assert(tb->width);
99 assert(tb->height);
100 }
101
102
103 Note that we typically do not use typedefs to make "class names"; we use
104 'struct whatever' everywhere.
105
106 Gallium's pipe_context and the subclassed psb_context, etc are prime examples
107 of this. There's also many examples in Mesa and the Mesa state tracker.