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cpp.texi: Update multichar charconst docs.

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doc:
	* cpp.texi: Update multichar charconst docs.
testsuite:
	* gcc.dg/cpp/charconst-3.c: New test.

From-SVN: r53202
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Neil Booth 2002-05-05 23:45:06 +00:00 committed by Neil Booth
parent 49f8e94b6b
commit 95ff5d3fad
4 changed files with 65 additions and 8 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2002-05-06 Neil Booth <neil@daikokuya.demon.co.uk>
doc:
* cpp.texi: Update multichar charconst docs.
2002-05-06 Neil Booth <neil@daikokuya.demon.co.uk>
* cpplex.c (cpp_interpret_charconst): Sign-extend each

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gcc/doc/cpp.texi
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@ -3508,17 +3508,25 @@ same column as it did in the original source file.
@item The numeric value of character constants in preprocessor expressions.
The preprocessor and compiler interpret character constants in the same
way; escape sequences such as @samp{\a} are given the values they would
have on the target machine.
The preprocessor and compiler interpret character constants in the
same way; i.e.@: escape sequences such as @samp{\a} are given the
values they would have on the target machine.
Multi-character character constants are interpreted a character at a
time, shifting the previous result left by the number of bits per
character on the host, and adding the new character. For example, 'ab'
on an 8-bit host would be interpreted as @w{'a' * 256 + 'b'}. If there
are more characters in the constant than can fit in the widest native
integer type on the host, usually a @code{long}, the excess characters
are ignored and a diagnostic is given.
target character and adding the sign-extended value of the new
character. They have type @code{int}, and are treated as signed
regardless of whether single characters are signed or not. If there
are more characters in the constant than would fit in the target
@code{int}, a diagnostic is given, and the excess leading characters
are ignored. This methodology is not fully compatible with versions
3.1 and earlier of GCC, which used a confusing and inconsistent
valuation technique.
For example, 'ab' for a target with an 8-bit @code{char} would be
interpreted as @w{'a' * 256 + 'b'}, and 'a\234' as @w{'a' * 256 +
'\234'}. GCC 3.1 and earlier would give a different value for the
latter example, probably @w{'a' * 256 + (unsigned char) '\234'}.
@item Source file inclusion.

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gcc/testsuite/ChangeLog
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2002-05-06 Neil Booth <neil@daikokuya.demon.co.uk>
* gcc.dg/cpp/charconst-3.c: New test.
2002-05-05 Neil Booth <neil@daikokuya.demon.co.uk>
* gcc.dg/cpp/charconst.c: Update tests.

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gcc/testsuite/gcc.dg/cpp/charconst-3.c Normal file
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/* Copyright (C) 2001 Free Software Foundation, Inc. */
/* { dg-do compile } */
/* { dg-options -Wno-multichar } */
/* This tests values and signedness of multichar charconsts.
Neil Booth, 5 May 2002. */
#include <limits.h>
int main ()
{
/* These tests require at least 2-byte ints. 8-) */
#if INT_MAX > 127
int scale = (int) (unsigned char) -1 + 1;
if ('ab' != ('a' * scale + 'b'))
abort ();
if ('\234b' != ('\234' * scale + 'b'))
abort ();
if ('b\234' != ('b' * scale + '\234'))
abort ();
/* Multichar charconsts have type int and should be signed. */
#if INT_MAX == 32767
if ('\234a' > 0)
abort ();
#elif INT_MAX == 2147483647
if ('\234aaa' > 0)
abort ();
#elif INT_MAX == 9223372036854775807
if ('\234aaaaaaa' > 0)
abort ();
#endif
#endif
return 0;
}