136 lines
3.9 KiB
Groff
136 lines
3.9 KiB
Groff
.\" Copyright (c) 2011 Kai Wang
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $Id: dwarf_new_expr.3 2074 2011-10-27 03:34:33Z jkoshy $
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.\"
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.Dd September 8, 2011
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.Os
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.Dt DWARF_NEW_EXPR 3
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.Sh NAME
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.Nm dwarf_new_expr
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.Nd create a location expression descriptor
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.Sh LIBRARY
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.Lb libdwarf
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.Sh SYNOPSIS
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.In libdwarf.h
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.Ft "Dwarf_P_Expr"
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.Fo dwarf_new_expr
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.Fa "Dwarf_P_Debug dbg"
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.Fa "Dwarf_Error *err"
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.Fc
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.Sh DESCRIPTION
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Function
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.Fn dwarf_new_expr
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allocates a DWARF location expression descriptor used to build up a
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location expression stream.
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.Pp
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The application can use the functions
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.Xr dwarf_add_expr_gen 3
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and
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.Xr dwarf_add_expr_addr_b 3
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to add location expression operators to the created descriptor.
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When done, the application can call the function
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.Xr dwarf_expr_into_block 3
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to retrieve the generated byte stream for the location expression,
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or call the function
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.Xr dwarf_add_AT_location_expr 3
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to create an attribute with the location expression stream as its
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value.
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.Pp
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Argument
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.Ar dbg
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should reference a DWARF producer instance allocated using
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.Xr dwarf_producer_init 3
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or
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.Xr dwarf_producer_init_b 3 .
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.Pp
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If argument
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.Ar err
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is not NULL, it will be used to store error information in case
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of an error.
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.Sh RETURN VALUES
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On success, function
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.Fn dwarf_new_expr
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returns the created location expression descriptor.
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In case of an error, function
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.Fn dwarf_new_expr
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returns
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.Dv DW_DLV_BADADDR
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and sets the argument
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.Ar err .
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.Sh ERRORS
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Function
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.Fn dwarf_new_expr
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can fail with:
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.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
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.It Bq Er DW_DLE_ARGUMENT
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Argument
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.Ar dbg
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was NULL.
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.It Bq Er DW_DLE_MEMORY
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An out of memory condition was encountered during the execution of
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the function.
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.El
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.Sh EXAMPLES
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To create a location expression descriptor, add location expression
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operators to it and to retrieve the generated byte stream,
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use:
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.Bd -literal -offset indent
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Dwarf_P_Debug dbg;
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Dwarf_Error de;
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Dwarf_P_Expr pe;
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Dwarf_Addr buf;
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Dwarf_Unsigned len;
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/* ...Assume that `dbg' refers to a DWARF producer instance... */
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if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) {
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warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1));
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return;
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}
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if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) ==
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DW_DLV_NOCOUNT) {
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warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1));
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return;
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}
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if ((buf = dwarf_expr_into_block(pe, &len, &de)) ==
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DW_DLV_BADADDR) {
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warnx("dwarf_expr_into_block failed: %s",
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dwarf_errmsg(-1));
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return;
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}
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.Ed
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.Sh SEE ALSO
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.Xr dwarf 3 ,
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.Xr dwarf_add_AT_location_expr 3 ,
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.Xr dwarf_add_expr_gen 3 ,
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.Xr dwarf_add_expr_addr 3 ,
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.Xr dwarf_add_expr_addr_b 3 ,
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.Xr dwarf_expr_current_offset 3 ,
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.Xr dwarf_expr_into_block 3 ,
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.Xr dwarf_producer_init 3 ,
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.Xr dwarf_producer_init_b 3
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