blob: 14a9dee33fc34f89a581de7d4d7c99ec13a3a526 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
|
CENV(9)
========
:doctype: manpage
:man source: X15
:man manual: X15 C environment
NAME
----
cenv - C environment
DESCRIPTION
-----------
This document describes the C environment of the kernel, including
available standard headers and interfaces.
Standard
~~~~~~~~
X15 must be built with a C compiler supporting the ISO/IEC 9899:2011
(C11) specification with some GCC extensions. It can currently be built
with the GCC and Clang compilers.
Environment
~~~~~~~~~~~
The kernel uses the freestanding execution environment. This means the
compiler is expected to provide the following headers :
** cheader:float
** cheader:iso646
** cheader:limits
** cheader:stdalign
** cheader:stdarg
** cheader:stdbool
** cheader:stddef
** cheader:stdint
** cheader:stdnoreturn
X15 augments the environment with a small subset of the functions provided
in hosted environments. The additional headers are :
** cheader:assert
** cheader:errno
** cheader:limits
** cheader:stdio
** cheader:string
Note that these headers do not provide the complete set of interfaces
expected in a hosted environment.
Formatting functions
~~~~~~~~~~~~~~~~~~~~
Of particular interest is the cheader:stdio header which provides a subset
of the printf and scanf family of functions.
The supported functions are :
** cfunction:getchar
** cfunction:putchar
** cfunction:sprintf
** cfunction:snprintf
** cfunction:vsprintf
** cfunction:vsnprintf
** cfunction:sscanf
** cfunction:vsscanf
The *EOF* macro is also provided.
The formatting functions only implement a subset of what the standard
defines, namely :
** cfunction:sprintf :
*** flags: # 0 - ' ' (space) +
*** field width is supported
*** precision is supported
** cfunction:sscanf :
*** flags: *
*** field width is supported
** common to both :
*** modifiers: hh h l ll z t
*** specifiers: d i o u x X c s p n %
Floating point conversions are currently not supported, but this may change
in the future.
SEE
---
manpage:intro
{x15-operating-system}
|
