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dwarf_loclist_from_expr(3) [freebsd man page]

DWARF_LOCLIST_FROM_EXPR(3)				   BSD Library Functions Manual 				DWARF_LOCLIST_FROM_EXPR(3)

NAME
dwarf_loclist_from_expr, dwarf_loclist_from_expr_a, dwarf_loclist_from_expr_b -- translate DWARF location expression bytes LIBRARY
DWARF Access Library (libdwarf, -ldwarf) SYNOPSIS
#include <libdwarf.h> int dwarf_loclist_from_expr(Dwarf_Debug dbg, Dwarf_Ptr bytes_in, Dwarf_Unsigned bytes_len, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *err); int dwarf_loclist_from_expr_a(Dwarf_Debug dbg, Dwarf_Ptr bytes_in, Dwarf_Unsigned bytes_len, Dwarf_Half addr_size, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *err); int dwarf_loclist_from_expr_b(Dwarf_Debug dbg, Dwarf_Ptr bytes_in, Dwarf_Unsigned bytes_len, Dwarf_Half addr_size, Dwarf_Half offset_size, Dwarf_Small version, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *error); DESCRIPTION
Function dwarf_loclist_from_expr() translates DWARF location expression bytes into a Dwarf_Locdesc descriptor. The size for address related data is taken to be the default address size for the object being read. Argument dbg should reference a DWARF debug context allocated using dwarf_init(3). Argument bytes_in should point to an array of DWARF location expression bytes. Argument bytes_len should specify the number of the location expression bytes to be translated. Argument llbuf should point to a location which will be set to a pointer to a returned Dwarf_Locdesc descriptor. Argument listlen should point to a location which will hold the number of the Dwarf_Locdesc descriptors returned. In this case it is always set to 1. If argument err is not NULL, it will be used to store error information in case of an error. Function dwarf_loclist_from_expr_a() is identical to function dwarf_loclist_from_expr(), except that it requires one additional argument addr_size, which specifies the address size to use when translating the location expression bytes. Function dwarf_loclist_from_expr_b() is identical to function dwarf_loclist_from_expr_a() except that it requires two additional arguments for translating the location expression bytes. Argument offset_size specifies the offset size, and argument version specifies the DWARF ver- sion. These values are required to correctly translate the DW_OP_GNU_implicit_pointer opcode. Memory Management The memory area used for the descriptor returned in argument llbuf is allocated by DWARF Access Library (libdwarf, -ldwarf). When the descriptor is no longer needed, application code should use function dwarf_dealloc(3) to free the memory area in two steps: 1. First, the array of Dwarf_Loc descriptors pointed to by the ld_s field of the Dwarf_Locdesc descriptor should be deallocated using the allocation type DW_DLA_LOC_BLOCK. 2. Next, the application should free the llbuf pointer using the allocation type DW_DLA_LOCDESC. 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 may fail with the following errors: [DW_DLE_ARGUMENT] One of the arguments dbg, bytes_in, llbuf or listlen was NULL. [DW_DLE_ARGUMENT] Argument bytes_len was 0. [DW_DLE_ARGUMENT] The value of argument addr_size was invalid. [DW_DLE_LOC_EXPR_BAD] An unknown or invalid operation was found in the location expression bytes provided in argument bytes_in. [DW_DLE_MEMORY] An out of memory condition was encountered during the execution of this function. SEE ALSO
dwarf(3), dwarf_dealloc(3), dwarf_loclist_n(3), dwarf_get_fde_info_for_all_regs3(3), dwarf_get_fde_info_for_cfa_reg3(3), dwarf_get_fde_info_for_reg3(3), dwarf_get_loclist_entry(3) BSD
December 21, 2014 BSD

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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

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