DWARF_ADD_EXPR_GEN(3) BSD Library Functions Manual DWARF_ADD_EXPR_GEN(3)NAME
dwarf_add_expr_gen -- add an operator to a location expression descriptor
LIBRARY
DWARF Access Library (libdwarf, -ldwarf)
SYNOPSIS
#include <libdwarf.h>
Dwarf_Unsigned
dwarf_add_expr_gen(Dwarf_P_Expr expr, Dwarf_Small opcode, Dwarf_Unsigned val1, Dwarf_Unsigned val2, Dwarf_Error *err);
DESCRIPTION
Function dwarf_add_expr_gen() adds a location expression operator to the location expression descriptor referenced by argument expr.
Argument expr should reference a location expression descriptor allocated using the function dwarf_new_expr(3).
Argument opcode specifies the operation code of the location expression operator. Valid values for this argument are those denoted by the
DW_OP_* constants defined in <libdwarf.h>.
To generate a DW_OP_addr operation, application code should instead use dwarf_add_expr_addr_b(3).
Argument val1 specifies the first operand of the location expression operator.
Argument val2 specifies the second operand of the location expression operator.
If argument err is not NULL, it will be used to store error information in case of an error.
RETURN VALUES
On success, function dwarf_add_expr_gen() returns the size in bytes of the location expression byte stream generated. In case of an error,
function dwarf_add_expr_gen() returns DW_DLV_NOCOUNT and sets the argument err.
ERRORS
Function dwarf_add_expr_gen() can fail with:
[DW_DLE_ARGUMENT] Argument expr was NULL.
[DW_DLE_LOC_EXPR_BAD] The operation code specified in argument opcode was invalid.
[DW_DLE_MEMORY] An out of memory condition was encountered during the execution of the function.
SEE ALSO dwarf(3), dwarf_add_AT_location_expr(3), dwarf_add_expr_addr(3), dwarf_add_expr_addr_b(3), dwarf_expr_current_offset(3),
dwarf_expr_into_block(3), dwarf_new_expr(3)BSD September 9, 2011 BSD
Check Out this Related Man Page
DWARF_LOCLIST(3) BSD Library Functions Manual DWARF_LOCLIST(3)NAME
dwarf_loclist, dwarf_loclist_n -- retrieve DWARF location expression information
LIBRARY
DWARF Access Library (libdwarf, -ldwarf)
SYNOPSIS
#include <libdwarf.h>
int
dwarf_loclist(Dwarf_Attribute at, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);
int
dwarf_loclist_n(Dwarf_Attribute at, Dwarf_Locdesc ***llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);
DESCRIPTION
These functions retrieve the location expressions associated with a DWARF attribute.
Note: function dwarf_loclist() is deprecated. New application code should instead use function dwarf_loclist_n()
Function dwarf_loclist_n() retrieves the list of location expressions associated with a DWARF attribute. Argument at should reference a
valid DWARF attribute. Argument llbuf should point to a location which will hold a returned array of pointers to Dwarf_Locdesc descriptors.
Argument listlen should point to a location which will be set to the number of elements contained in the returned array. If argument err is
not NULL, it will be used to store error information in case of an error.
Function dwarf_loclist() retrieves the first location expression associated with an attribute. Argument at should reference a valid DWARF
attribute. Argument llbuf should point to a location which will hold the returned pointer to a Dwarf_Locdesc descriptor. Argument listlen
should point to a location which will be always set to 1. If argument err is not NULL, it will be used to store error information in case of
an error.
Dwarf_Locdesc descriptors are defined in the header file <libdwarf.h>, and consist of following fields:
ld_lopc The lowest program counter address covered by the descriptor. This field will be set to 0 if the descriptor is not associated with
an address range.
ld_hipc The highest program counter address covered by the descriptor. This field will be set to 0 if the descriptor is not associated
with an address range.
ld_cents The number of entries returned in ld_s field.
ld_s Pointer to an array of Dwarf_Loc descriptors.
Each Dwarf_Loc descriptor represents one operation of a location expression. These descriptors are defined in the header file <libdwarf.h>,
and consist of following fields:
lr_atom The operator name, one of the DW_OP_* constants defined in the header file <dwarf.h>.
lr_number The first operand of this operation.
lr_number2 The second operand of this operation.
lr_offset The byte offset of this operation within the containing location expression.
Memory Management
The memory area used for the descriptor array returned in argument llbuf is allocated by the DWARF Access Library (libdwarf, -ldwarf). When
the descriptor array is no longer needed, application code should use function dwarf_dealloc(3) to free the memory area in the following man-
ner:
1. First, the ld_s field of each Dwarf_Locdesc descriptor should be deallocated using the allocation type DW_DLA_LOC_BLOCK.
2. Then, the application should free each Dwarf_Locdesc descriptor using the allocation type DW_DLA_LOCDESC.
3. Finally, the llbuf pointer should be deallocated using the allocation type DW_DLA_LIST.
RETURN VALUES
On success, these functions returns DW_DLV_OK. In case of an error, they return DW_DLV_ERROR and set the argument err.
ERRORS
These functions can fail with:
[DW_DLE_ARGUMENT] One of the arguments at, llbuf or listlen was NULL.
[DW_DLE_ARGUMENT] The attribute provided by argument at does not contain a location expression or is not associated with a location expres-
sion list.
EXAMPLE
To retrieve the location list associated with an attribute, use:
Dwarf_Attribute at;
Dwarf_Locdesc **llbuf;
Dwarf_Signed lcnt;
Dwarf_Loc *lr;
Dwarf_Error de;
int i;
if (dwarf_loclist_n(at, &llbuf, &lcnt, &de) != DW_DLV_OK)
errx(EXIT_FAILURE, "dwarf_loclist_n failed: %s",
dwarf_errmsg(de));
for (i = 0; i < lcnt; i++) {
/* ... Use llbuf[i] ... */
for (j = 0; (Dwarf_Half) j < llbuf[i]->ld_cents; j++) {
lr = &llbuf[i]->ld_s[j];
/* ... Use each Dwarf_Loc descriptor ... */
}
dwarf_dealloc(dbg, llbuf[i]->ld_s, DW_DLA_LOC_BLOCK);
dwarf_dealloc(dbg, llbuf[i], DW_DLA_LOCDESC);
}
dwarf_dealloc(dbg, llbuf, DW_DLA_LIST);
SEE ALSO dwarf(3), dwarf_dealloc(3), dwarf_loclist_from_expr(3), dwarf_loclist_from_expr_a(3), dwarf_get_loclist_entry(3)BSD November 9, 2011 BSD