144 lines
4 KiB
Text
144 lines
4 KiB
Text
--- ./gcc/doc/extend.texi.orig Sat Aug 6 15:26:27 2005
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+++ ./gcc/doc/extend.texi Mon Aug 22 00:14:05 2005
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@@ -79,6 +79,7 @@
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* Pragmas:: Pragmas accepted by GCC.
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* Unnamed Fields:: Unnamed struct/union fields within structs/unions.
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* Thread-Local:: Per-thread variables.
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+* Binary constants:: Binary constants using the @samp{0b} prefix.
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@end menu
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@node Statement Exprs
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@@ -9742,6 +9743,28 @@
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Non-@code{static} members shall not be @code{__thread}.
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@end quotation
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@end itemize
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+
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+@node Binary constants
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+@section Binary constants using the @samp{0b} prefix
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+@cindex Binary constants using the @samp{0b} prefix
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+
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+Integer constants can be written as binary constants, consisting of a
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+sequence of @samp{0} and @samp{1} digits, prefixed by @samp{0b} or
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+@samp{0B}. This is particularly useful in environments that operate a
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+lot on the bit-level (like microcontrollers).
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+
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+The following statements are identical:
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+
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+@smallexample
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+i = 42;
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+i = 0x2a;
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+i = 052;
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+i = 0b101010;
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+@end smallexample
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+
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+The type of these constants follows the same rules as for octal or
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+hexadecimal integer constants, so suffixes like @samp{L} or @samp{UL}
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+can be applied.
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@node C++ Extensions
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@chapter Extensions to the C++ Language
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--- ./libcpp/include/cpplib.h.orig Wed Jun 29 04:34:39 2005
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+++ ./libcpp/include/cpplib.h Mon Aug 22 00:14:05 2005
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@@ -729,6 +729,7 @@
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#define CPP_N_DECIMAL 0x0100
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#define CPP_N_HEX 0x0200
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#define CPP_N_OCTAL 0x0400
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+#define CPP_N_BINARY 0x0800
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#define CPP_N_UNSIGNED 0x1000 /* Properties. */
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#define CPP_N_IMAGINARY 0x2000
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--- ./libcpp/expr.c.orig Wed Jun 29 04:34:36 2005
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+++ ./libcpp/expr.c Mon Aug 22 12:02:28 2005
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@@ -171,6 +171,11 @@
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radix = 16;
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str++;
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}
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+ else if ((*str == 'b' || *str == 'B') && (str[1] == '0' || str[1] == '1'))
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+ {
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+ radix = 2;
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+ str++;
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+ }
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}
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/* Now scan for a well-formed integer or float. */
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@@ -209,10 +214,22 @@
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radix = 10;
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if (max_digit >= radix)
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- SYNTAX_ERROR2 ("invalid digit \"%c\" in octal constant", '0' + max_digit);
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+ {
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+ if (radix == 2)
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+ SYNTAX_ERROR2 ("invalid digit \"%c\" in binary constant", '0' + max_digit);
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+ else
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+ SYNTAX_ERROR2 ("invalid digit \"%c\" in octal constant", '0' + max_digit);
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+ }
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if (float_flag != NOT_FLOAT)
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{
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+ if (radix == 2)
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+ {
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+ cpp_error (pfile, CPP_DL_ERROR,
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+ "invalid prefix \"0b\" for floating constant");
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+ return CPP_N_INVALID;
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+ }
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+
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if (radix == 16 && CPP_PEDANTIC (pfile) && !CPP_OPTION (pfile, c99))
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cpp_error (pfile, CPP_DL_PEDWARN,
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"use of C99 hexadecimal floating constant");
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@@ -288,11 +305,16 @@
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if ((result & CPP_N_IMAGINARY) && CPP_PEDANTIC (pfile))
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cpp_error (pfile, CPP_DL_PEDWARN,
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"imaginary constants are a GCC extension");
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+ if (radix == 2 && CPP_PEDANTIC (pfile))
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+ cpp_error (pfile, CPP_DL_PEDWARN,
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+ "binary constants are a GCC extension");
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if (radix == 10)
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result |= CPP_N_DECIMAL;
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else if (radix == 16)
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result |= CPP_N_HEX;
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+ else if (radix == 2)
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+ result |= CPP_N_BINARY;
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else
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result |= CPP_N_OCTAL;
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@@ -343,6 +365,11 @@
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base = 16;
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p += 2;
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}
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+ else if ((type & CPP_N_RADIX) == CPP_N_BINARY)
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+ {
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+ base = 2;
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+ p += 2;
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+ }
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/* We can add a digit to numbers strictly less than this without
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needing the precision and slowness of double integers. */
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@@ -398,12 +425,25 @@
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append_digit (cpp_num num, int digit, int base, size_t precision)
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{
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cpp_num result;
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- unsigned int shift = 3 + (base == 16);
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+ unsigned int shift;
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bool overflow;
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cpp_num_part add_high, add_low;
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- /* Multiply by 8 or 16. Catching this overflow here means we don't
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+ /* Multiply by 2, 8 or 16. Catching this overflow here means we don't
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need to worry about add_high overflowing. */
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+ switch (base)
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+ {
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+ case 2:
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+ shift = 1;
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+ break;
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+
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+ case 16:
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+ shift = 4;
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+ break;
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+
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+ default:
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+ shift = 3;
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+ }
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overflow = !!(num.high >> (PART_PRECISION - shift));
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result.high = num.high << shift;
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result.low = num.low << shift;
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