From 3bce82377f683870cc89925ff43aefb7dcce4a77 Mon Sep 17 00:00:00 2001 From: Sanimir Agovic Date: Wed, 5 Feb 2014 16:22:08 +0000 Subject: vla: evaluate operand of sizeof if its type is a vla The c99 standard in "6.5.3.4 The sizeof operator" states: If the type of the operand is a variable length array type, the operand is evaluated;[...] This patch mirrors the following c99 semantic in gdb: 1| int vla[n][m]; 2| int i = 1; 3| sizeof(vla[i++][0]); // No sideffect 4| assert (i == 1); 5| sizeof(vla[i++]); // With sideffect 6| assert (i == 2); Note: ptype/whatsis still do not allow any sideeffects. This patch was motivated by: https://sourceware.org/ml/gdb-patches/2014-01/msg00732.html * eval.c (evaluate_subexp_for_sizeof): Add enum noside argument. (evaluate_subexp_standard): Pass noside argument. (evaluate_subexp_for_sizeof) : Handle subscript case if noside equals EVAL_NORMAL. If the subscript yields a vla type re-evaluate subscript operation with EVAL_NORMAL to enable sideffects. * gdbtypes.c (resolve_dynamic_bounds): Mark bound as evaluated. * gdbtypes.h (enum range_flags): Add RANGE_EVALUATED case. testsuite/gdb.base/ * vla-sideeffect.c: New file. * vla-sideeffect.exp: New file. --- gdb/eval.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) (limited to 'gdb/eval.c') diff --git a/gdb/eval.c b/gdb/eval.c index 1074e1d..d29960a 100644 --- a/gdb/eval.c +++ b/gdb/eval.c @@ -50,7 +50,8 @@ extern int overload_resolution; /* Prototypes for local functions. */ -static struct value *evaluate_subexp_for_sizeof (struct expression *, int *); +static struct value *evaluate_subexp_for_sizeof (struct expression *, int *, + enum noside); static struct value *evaluate_subexp_for_address (struct expression *, int *, enum noside); @@ -2562,7 +2563,7 @@ evaluate_subexp_standard (struct type *expect_type, evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP); goto nosideret; } - return evaluate_subexp_for_sizeof (exp, pos); + return evaluate_subexp_for_sizeof (exp, pos, noside); case UNOP_CAST: (*pos) += 2; @@ -2997,10 +2998,13 @@ evaluate_subexp_with_coercion (struct expression *exp, /* Evaluate a subexpression of EXP, at index *POS, and return a value for the size of that subexpression. - Advance *POS over the subexpression. */ + Advance *POS over the subexpression. If NOSIDE is EVAL_NORMAL + we allow side-effects on the operand if its type is a variable + length array. */ static struct value * -evaluate_subexp_for_sizeof (struct expression *exp, int *pos) +evaluate_subexp_for_sizeof (struct expression *exp, int *pos, + enum noside noside) { /* FIXME: This should be size_t. */ struct type *size_type = builtin_type (exp->gdbarch)->builtin_int; @@ -3054,6 +3058,37 @@ evaluate_subexp_for_sizeof (struct expression *exp, int *pos) return value_from_longest (size_type, (LONGEST) TYPE_LENGTH (type)); + /* Deal with the special case if NOSIDE is EVAL_NORMAL and the resulting + type of the subscript is a variable length array type. In this case we + must re-evaluate the right hand side of the subcription to allow + side-effects. */ + case BINOP_SUBSCRIPT: + if (noside == EVAL_NORMAL) + { + int pc = (*pos) + 1; + + val = evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_AVOID_SIDE_EFFECTS); + type = check_typedef (value_type (val)); + if (TYPE_CODE (type) == TYPE_CODE_ARRAY) + { + type = check_typedef (TYPE_TARGET_TYPE (type)); + if (TYPE_CODE (type) == TYPE_CODE_ARRAY) + { + type = TYPE_INDEX_TYPE (type); + /* Only re-evaluate the right hand side if the resulting type + is a variable length type. */ + if (TYPE_RANGE_DATA (type)->flag_bound_evaluated) + { + val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_NORMAL); + return value_from_longest + (size_type, (LONGEST) TYPE_LENGTH (value_type (val))); + } + } + } + } + + /* Fall through. */ + default: val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS); return value_from_longest (size_type, -- cgit v1.1