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
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
|
--- gcc/cpplib.h.orig Mon Feb 9 13:23:51 2004
+++ gcc/cpplib.h Thu Apr 29 12:24:10 2004
@@ -630,6 +630,7 @@
#define CPP_N_DECIMAL 0x0100
#define CPP_N_HEX 0x0200
#define CPP_N_OCTAL 0x0400
+#define CPP_N_BINARY 0x0800
#define CPP_N_UNSIGNED 0x1000 /* Properties. */
#define CPP_N_IMAGINARY 0x2000
--- gcc/cppexp.c.orig Thu Feb 12 00:52:56 2004
+++ gcc/cppexp.c Thu Apr 29 12:29:40 2004
@@ -22,6 +22,9 @@
#include "system.h"
#include "cpplib.h"
#include "cpphash.h"
+#include "flags.h"
+#include "coretypes.h"
+#include "toplev.h"
#define PART_PRECISION (sizeof (cpp_num_part) * CHAR_BIT)
#define HALF_MASK (~(cpp_num_part) 0 >> (PART_PRECISION / 2))
@@ -75,6 +78,9 @@
#define SYNTAX_ERROR2(msgid, arg) \
do { cpp_error (pfile, CPP_DL_ERROR, msgid, arg); goto syntax_error; } \
while(0)
+#define SYNTAX_ERROR3(msgid, arg1, arg2) \
+ do { cpp_error (pfile, CPP_DL_ERROR, msgid, arg1, arg2); goto syntax_error; } \
+ while(0)
/* Subroutine of cpp_classify_number. S points to a float suffix of
length LEN, possibly zero. Returns 0 for an invalid suffix, or a
@@ -171,6 +177,11 @@
radix = 16;
str++;
}
+ else if ((*str == 'b' || *str == 'B') && (str[1] == '0' || str[1] == '1'))
+ {
+ radix = 2;
+ str++;
+ }
}
/* Now scan for a well-formed integer or float. */
@@ -209,7 +220,8 @@
radix = 10;
if (max_digit >= radix)
- SYNTAX_ERROR2 ("invalid digit \"%c\" in octal constant", '0' + max_digit);
+ SYNTAX_ERROR3 ("invalid digit \"%c\" in %s constant", '0' + max_digit,
+ radix == 2? "binary": "octal");
if (float_flag != NOT_FLOAT)
{
@@ -288,11 +300,16 @@
if ((result & CPP_N_IMAGINARY) && CPP_PEDANTIC (pfile))
cpp_error (pfile, CPP_DL_PEDWARN,
"imaginary constants are a GCC extension");
+ if (radix == 2 && CPP_PEDANTIC (pfile))
+ cpp_error (pfile, CPP_DL_PEDWARN,
+ "binary constants are a GCC extension");
if (radix == 10)
result |= CPP_N_DECIMAL;
else if (radix == 16)
result |= CPP_N_HEX;
+ else if (radix == 2)
+ result |= CPP_N_BINARY;
else
result |= CPP_N_OCTAL;
@@ -341,6 +358,11 @@
else if ((type & CPP_N_RADIX) == CPP_N_HEX)
{
base = 16;
+ p += 2;
+ }
+ else if ((type & CPP_N_RADIX) == CPP_N_BINARY)
+ {
+ base = 2;
p += 2;
}
--- gcc/doc/extend.texi.orig Wed Jun 9 20:31:59 2004
+++ gcc/doc/extend.texi Wed Jul 7 20:51:58 2004
@@ -475,6 +475,7 @@
* Pragmas:: Pragmas accepted by GCC.
* Unnamed Fields:: Unnamed struct/union fields within structs/unions.
* Thread-Local:: Per-thread variables.
+* Binary constants:: Binary constants using the `0b' prefix.
@end menu
@node Statement Exprs
@@ -7648,6 +7649,26 @@
Non-@code{static} members shall not be @code{__thread}.
@end quotation
@end itemize
+
+@node Binary constants
+@section Binary constants using the `0b' prefix
+@cindex Binary constants using the `0b' prefix
+
+@emph{Note:} This is currently a private extension of AVR-GCC.
+
+Integer constants can be written as binary constants, consisting of a
+sequence of `0' and `1' digits, prefixed by `0b'. This is
+particularly useful in environments that operate a lot on the
+bit-level (like microcontrollers).
+
+The following statements are identical:
+
+@smallexample
+i = 42;
+i = 0x2a;
+i = 052;
+i = 0b101010;
+@end smallexample
@node C++ Extensions
@chapter Extensions to the C++ Language
|
