.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_get_macro_details.3 3644 2018-10-15 19:55:01Z jkoshy $
.\"
.Dd March 20, 2011
.Dt DWARF_GET_MACRO_DETAILS 3
.Os
.Sh NAME
.Nm dwarf_get_macro_details
.Nd retrieve macro information
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_get_macro_details
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Off offset"
.Fa "Dwarf_Unsigned max_count"
.Fa "Dwarf_Signed *entry_cnt"
.Fa "Dwarf_Macro_Details **details"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_get_macro_details
retrieves information about macros associated with a DWARF debug
context.
Information about macro entries are returned as an array of
descriptors of type
.Vt Dwarf_Macro_Details ,
with each
.Vt Dwarf_Macro_Details
descriptor describing one macro information entry.
.Pp
Argument
.Ar dbg
should reference a DWARF debug context allocated using
.Xr dwarf_init 3 .
Argument
.Ar offset
is an offset, relative to the
.Dq ".debug_macinfo"
section, to the start of the desired macro information.
Argument
.Ar max_count
specifies the maximum number of macro information entries
to be returned, or 0 if all entries are to be returned.
Argument
.Ar entry_cnt
should point to a location that will be set to the number
of entries actually returned.
Argument
.Ar details
should point to a location that will be set to a pointer to
an array of
.Vt Dwarf_Macro_Details
descriptors.
If argument
.Ar err
is not NULL, it will be used to store error information in case
of an error.
.Pp
.Vt Dwarf_Macro_Details
descriptors are defined in the header file
.In libdwarf.h ,
and consist of the following fields:
.Bl -tag -width ".Va dmd_fileindex" -compact
.It Va dmd_offset
The section-relative offset within the
.Dq ".debug_macinfo"
section of the macro information entry being described.
.It Va dmd_type
The type code of this macro information entry; one of the
.Dv DW_MACINFO_*
constants defined by the DWARF specification.
.It Va dmd_lineno
The line number associated with the macro information
entry, or 0 if there is no applicable line number.
.It Va dmd_fileindex
The source file index for the macro information entry.
This field is only meaningful when
.Va dmd_type
field is set to
.Dv DW_MACINFO_start_file .
.It Va dmd_macro
The contents of this field is a pointer to a NUL-terminated string
whose meaning depends on the value of the
.Va dmd_type
field:
.Bl -tag -width ".Dv DW_MACINFO_vendor_ext" -compact
.It Dv DW_MACINFO_define
The returned string contains the macro name and value.
.It Dv DW_MACINFO_undef
The string holds the macro name.
.It Dv DW_MACINFO_vendor_ext
The
.Va dmd_macro
field points to a vendor defined string.
.El
The field is NULL for other values of
.Va dmd_type .
.El
.Ss Memory Management
The memory area used for the array of
.Vt Dwarf_Macro_Details
descriptors returned in argument
.Ar details
is owned by the
.Lb libdwarf .
The application should not attempt to directly free this pointer.
Portable code should instead use
.Fn dwarf_dealloc
with the allocation type
.Dv DW_DLA_STRING
to indicate that the memory may be freed.
.Sh RETURN VALUES
Function
.Fn dwarf_get_macro_details
returns
.Dv DW_DLV_OK
when it succeeds.
It returns
.Dv DW_DLV_NO_ENTRY
if there is no more macro information at the specified offset
.Ar offset .
In case of an error, it returns
.Dv DW_DLV_ERROR
and sets the argument
.Ar err .
.Sh EXAMPLES
To loop through all the macro information entries associated with
a DWARF debug context:
.Bd -literal -offset indent
Dwarf_Debug dbg;
Dwarf_Unsigned offset;
Dwarf_Signed cnt;
Dwarf_Macro_Details *md;
Dwarf_Error de;

offset = 0;
while (dwarf_get_macro_details(dbg, offset, 0,
    &cnt, &md, &de) == DW_DLV_OK) {
	for (i = 0; i < cnt; i++) {
		/* Access fields of md[i] ... */
	}
	offset = md[cnt - 1].dmd_offset + 1;
}
.Ed
.Sh ERRORS
Function
.Fn dwarf_get_macro_details
can fail with:
.Bl -tag -width ".Bq Er DW_DLE_NO_ENTRY"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Ar dbg ,
.Ar entry_cnt
or
.Ar details
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
There is no more macro information at the specified offset
.Ar offset .
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_dealloc 3 ,
.Xr dwarf_find_macro_value_start 3 ,
.Xr dwarf_init 3