RFA: fix PR 2506

[Tom Tromey <tromey@redhat.com>]

PR 2506 is about string concatenation.

Something like "x" "y" is a valid C expression.  However, gdb does not
parse it.

The simplest fix was to add a new production that handles string
concatenation.  I looked at doing this in the lexer, but that is
tricky due to macro expansion.

The memory allocation is handled the way it is in order to ensure that
strings are always freed.  (If we allocated a new string in the lexer
it would leak if the string occurred in a syntactically invalid
place.)

Built & regtested on x86-64 (compile farm).
New test case included.

Ok?

Tom

2008-08-20  Tom Tromey  <tromey@redhat.com>

	PR gdb/2506:
	* c-exp.y (string_exp): New production.
	(exp): Use it.

2008-08-20  Tom Tromey  <tromey@redhat.com>

	* gdb.base/exprs.exp (test_expr): Add test for string
	concatenation.

diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index bd04dc2..be79f15 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -182,7 +182,7 @@ static int parse_number (char *, int, int, YYSTYPE *);
 %token <ssym> NAME /* BLOCKNAME defined below to give it higher precedence. */
 %token <voidval> COMPLETE
 %token <tsym> TYPENAME
-%type <sval> name
+%type <sval> name string_exp
 %type <ssym> name_not_typename
 %type <tsym> typename
 
@@ -560,7 +560,36 @@ exp	:	SIZEOF '(' type ')'	%prec UNARY
 			  write_exp_elt_opcode (OP_LONG); }
 	;
 
-exp	:	STRING
+string_exp:
+		STRING
+			{
+			  /* We copy the string here, and not in the
+			     lexer, to guarantee that we do not leak a
+			     string.  Note that we follow the
+			     NUL-termination convention of the
+			     lexer.  */
+			  $$.length = $1.length;
+			  $$.ptr = xmalloc ($1.length + 1);
+			  memcpy ($$.ptr, $1.ptr, $1.length + 1);
+			}
+
+	|	string_exp STRING
+			{
+			  /* Note that we NUL-terminate here, but just
+			     for convenience.  */
+			  struct stoken t;
+			  t.length = $1.length + $2.length;
+			  t.ptr = xmalloc (t.length + 1);
+			  memcpy (t.ptr, $1.ptr, $1.length);
+			  memcpy (t.ptr + $1.length, $2.ptr, $2.length);
+			  t.ptr[t.length] = '\0';
+			  xfree ($1.ptr);
+			  xfree ($2.ptr);
+			  $$ = t;
+			}
+		;
+
+exp	:	string_exp
 			{ /* C strings are converted into array constants with
 			     an explicit null byte added at the end.  Thus
 			     the array upper bound is the string length.
@@ -581,7 +610,9 @@ exp	:	STRING
 			  write_exp_elt_opcode (OP_ARRAY);
 			  write_exp_elt_longcst ((LONGEST) 0);
 			  write_exp_elt_longcst ((LONGEST) ($1.length));
-			  write_exp_elt_opcode (OP_ARRAY); }
+			  write_exp_elt_opcode (OP_ARRAY);
+			  xfree ($1.ptr);
+			}
 	;
 
 /* C++.  */
diff --git a/gdb/testsuite/gdb.base/exprs.exp b/gdb/testsuite/gdb.base/exprs.exp
index e25de77..ad60aad 100644
--- a/gdb/testsuite/gdb.base/exprs.exp
+++ b/gdb/testsuite/gdb.base/exprs.exp
@@ -248,3 +248,6 @@ gdb_test "print (void*) ((long long) (unsigned long) -1 + 1)" \
 if [expr ! $ok] { setup_xfail "*-*-*" }
 gdb_test "print (void*) (~((long long)(unsigned long) -1) - 1)" \
 	"warning: value truncated.*" "truncate (void*) 0xffffffff00000000 - 1"
+
+# String concatentation.
+test_expr "print \"x\" \"y\"" "\\$\[0-9\]* = \"xy\""