c-common.c (warn_multichar): New.

	* c-common.c (warn_multichar): New.
	(c_common_init): Set CPP's warn_multichar.
	* c-common.h (warn_multichar): New.
	* c-decl.c (warn_multichar): Remove.
	* c-lex.c (lex_charconst): Update.
	* c-tree.h (warn_multichar): Remove.
	* cppexp.c (eval_token): Sign-extend charconst value.
	* cppinit.c (cpp_create_reader): Set warn_multichar.
	* cpplex.c (cpp_interpret_charconst): Don't sign-extend
	each character.  Update prototype.  Sign-extend the result.
	* cpplib.h: Fix conditions.
	(struct cpp_options): Add new warning flag.
	(cpp_interpret_charconst): Update prototype.
cp:
	* Make-lang.in (decl2.o): Update.
	* cp-tree.h (warn_multichar): Remove.
	* decl2.c: Include c-common.h.
	(warn_multichar): Remove.
doc:
	* cpp.texi: Update documentation.
testsuite:
	* gcc.dg/cpp/charconst-3.c: Correct tests accordingly.

From-SVN: r53240

1 files changed, 9 insertions, 11 deletions

diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 7ba498d..0e7d9e8 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -3514,19 +3514,17 @@ 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
-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.
+target character and or-ing the value of the new character truncated
+to the width of a target character.  They have type @code{int}, and
+are treated as signed regardless of whether single characters are
+signed or not (a slight change from versions 3.1 and earlier of GCC).
+If there are more characters in the constant than would fit in the
+target @code{int} an error is issued.
 
 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'}.
+interpreted as @w{(int) ((unsigned char) 'a' * 256 + (unsigned char)
+'b')}, and 'a\234' as @w{(int) ((unsigned char) 'a' * 256 + (unsigned
+char) '\234')}.
 
 @item Source file inclusion.