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* dwarf2expr.h (struct dwarf_expr_context): New members

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'num_pieces' and 'pieces', for returning the result of an
expression that uses DW_OP_piece.
(struct dwarf_expr_piece): New struct type.
* dwarf2expr.c (new_dwarf_expr_context): Initialize num_pieces and
pieces.
(free_dwarf_expr_context): Free pieces, if any.
(add_piece): New function.
(execute_stack_op): Implement DW_OP_piece.
* dwarf2loc.c (dwarf2_evaluate_loc_desc): If the result of the
expression is a list of pieces, print an error message.
(dwarf2_loc_desc_needs_frame): If the expression yields
pieces, and any piece is in a register, then we need a frame.
This commit is contained in:
Jim Blandy
2004-08-24 21:01:49 +00:00
parent 8d2c00cb73
commit 87808bd699
4 changed files with 120 additions and 2 deletions
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43
gdb/dwarf2expr.h
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@ -74,6 +74,49 @@ struct dwarf_expr_context
/* Non-zero if the result is in a register. The register number
will be on the expression stack. */
int in_reg;
/* An array of pieces. PIECES points to its first element;
NUM_PIECES is its length.
Each time DW_OP_piece is executed, we add a new element to the
end of this array, recording the current top of the stack, the
current in_reg flag, and the size given as the operand to
DW_OP_piece. We then pop the top value from the stack, clear the
in_reg flag, and resume evaluation.
The Dwarf spec doesn't say whether DW_OP_piece pops the top value
from the stack. We do, ensuring that clients of this interface
expecting to see a value left on the top of the stack (say, code
evaluating frame base expressions or CFA's specified with
DW_CFA_def_cfa_expression) will get an error if the expression
actually marks all the values it computes as pieces.
If an expression never uses DW_OP_piece, num_pieces will be zero.
(It would be nice to present these cases as expressions yielding
a single piece, with in_reg clear, so that callers need not
distinguish between the no-DW_OP_piece and one-DW_OP_piece cases.
But expressions with no DW_OP_piece operations have no value to
place in a piece's 'size' field; the size comes from the
surrounding data. So the two cases need to be handled
separately.) */
int num_pieces;
struct dwarf_expr_piece *pieces;
};
/* A piece of an object, as recorded by DW_OP_piece. */
struct dwarf_expr_piece
{
/* If IN_REG is zero, then the piece is in memory, and VALUE is its address.
If IN_REG is non-zero, then the piece is in a register, and VALUE
is the register number. */
int in_reg;
/* This piece's address or register number. */
CORE_ADDR value;
/* The length of the piece, in bytes. */
ULONGEST size;
};
struct dwarf_expr_context *new_dwarf_expr_context (void);