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Re: [patch] fix pre-/post- in-/decrement
On Wednesday, October 13, 2010 9:00:28 pm Tom Tromey wrote:
> Ken> I don't see how to control the type of the result of an operator
> Ken> there. I'm still quite new to the GDB parsing internals and would
> Ken> appreciate any insights.
>
> It is probably a bit of a pain, since the IR generated by the parser is
> a bit unusual (as compilers go).
>
> However, it seems to me that it would be much friendlier for users to
> report this as a parse error rather than a runtime error.
>
> One option would be to write a C/C++ implementation of the language_defn
> la_post_parser method, which would look at the expression to see if this
> constraint is violated.
>
> Another option would be to try to implement it in the grammar.
Ok - I see. Thanks for your suggestions. This seems to be something bigger and
could be implemented as part of a future patch :). I think for now the non-
language dependent parts of the patch would be sufficient.
The attached patch only contains the fix for the post in-/decrement operators
as this is what the vec_unop patch (http://sourceware.org/ml/gdb-
patches/2010-10/msg00031.html) prevents from going upstream.
Tested on i686-*-linux-gnu with no regressions.
OK to apply?
Regards
Ken
ChangeLog:
2010-10-18 Ken Werner <ken.werner@de.ibm.com>
* value.h (value_non_lval): Declare.
* value.c (value_non_lval): New function.
* eval.c (evaluate_subexp_standard) <UNOP_POSTINCREMENT,
UNOP_POSTDECREMENT>: Call value_non_lval to ensure to return a
non-lvalue.
testsuite/ChangeLog:
2010-10-18 Ken Werner <ken.werner@de.ibm.com>
* gdb.base/exprs.exp: Add tests for pre-/post- in-/decrement operators.
Index: gdb/eval.c
===================================================================
RCS file: /cvs/src/src/gdb/eval.c,v
retrieving revision 1.139
diff -p -u -r1.139 eval.c
--- gdb/eval.c 11 Aug 2010 16:48:26 -0000 1.139
+++ gdb/eval.c 18 Oct 2010 17:43:52 -0000
@@ -2739,6 +2739,8 @@ evaluate_subexp_standard (struct type *e
}
else
{
+ arg3 = value_non_lval (arg1);
+
if (ptrmath_type_p (exp->language_defn, value_type (arg1)))
arg2 = value_ptradd (arg1, 1);
else
@@ -2751,7 +2753,7 @@ evaluate_subexp_standard (struct type *e
}
value_assign (arg1, arg2);
- return arg1;
+ return arg3;
}
case UNOP_POSTDECREMENT:
@@ -2764,6 +2766,8 @@ evaluate_subexp_standard (struct type *e
}
else
{
+ arg3 = value_non_lval (arg1);
+
if (ptrmath_type_p (exp->language_defn, value_type (arg1)))
arg2 = value_ptradd (arg1, -1);
else
@@ -2776,7 +2780,7 @@ evaluate_subexp_standard (struct type *e
}
value_assign (arg1, arg2);
- return arg1;
+ return arg3;
}
case OP_THIS:
Index: gdb/value.c
===================================================================
RCS file: /cvs/src/src/gdb/value.c,v
retrieving revision 1.113
diff -p -u -r1.113 value.c
--- gdb/value.c 30 Sep 2010 18:58:07 -0000 1.113
+++ gdb/value.c 18 Oct 2010 17:43:52 -0000
@@ -826,6 +826,26 @@ value_copy (struct value *arg)
return val;
}
+/* Return a version of ARG that is non-lvalue. */
+
+struct value *
+value_non_lval (struct value *arg)
+{
+ if (VALUE_LVAL (arg) != not_lval)
+ {
+ struct type *enc_type = value_enclosing_type (arg);
+ struct value *val = allocate_value (enc_type);
+
+ memcpy (value_contents_all_raw (val), value_contents_all (arg),
+ TYPE_LENGTH (enc_type));
+ val->type = arg->type;
+ set_value_embedded_offset (val, value_embedded_offset (arg));
+ set_value_pointed_to_offset (val, value_pointed_to_offset (arg));
+ return val;
+ }
+ return arg;
+}
+
void
set_value_component_location (struct value *component,
const struct value *whole)
Index: gdb/value.h
===================================================================
RCS file: /cvs/src/src/gdb/value.h,v
retrieving revision 1.162
diff -p -u -r1.162 value.h
--- gdb/value.h 15 Oct 2010 18:54:13 -0000 1.162
+++ gdb/value.h 18 Oct 2010 17:43:52 -0000
@@ -711,6 +711,8 @@ extern void preserve_values (struct objf
extern struct value *value_copy (struct value *);
+extern struct value *value_non_lval (struct value *);
+
extern void preserve_one_value (struct value *, struct objfile *, htab_t);
/* From valops.c */
Index: gdb/testsuite/gdb.base/exprs.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/exprs.exp,v
retrieving revision 1.19
diff -p -u -r1.19 exprs.exp
--- gdb/testsuite/gdb.base/exprs.exp 10 Jun 2010 19:48:19 -0000 1.19
+++ gdb/testsuite/gdb.base/exprs.exp 18 Oct 2010 17:43:52 -0000
@@ -253,3 +253,12 @@ gdb_test "set output-radix 8" ".*"
test_expr "print red" "\\$\[0-9\]* = red"
test_expr "print/d red" "\\$\[0-9\]* = 0"
gdb_test "set output-radix 10" ".*"
+
+# Pre-/post in-/decrement tests.
+gdb_test "set variable v_int = 1" ""
+gdb_test "print v_int++" "\\$\[0-9\]* = 1"
+gdb_test "print ++v_int" "\\$\[0-9\]* = 3"
+gdb_test "print v_int--" "\\$\[0-9\]* = 3"
+gdb_test "print --v_int" "\\$\[0-9\]* = 1"
+gdb_test "print v_int++ = 5" "Left operand of assignment is not an lvalue."
+gdb_test "print v_int-- = 5" "Left operand of assignment is not an lvalue."