4.3BSD-UWisc/man/cat5/dbx.5
DBX(5) UNIX Programmer's Manual DBX(5)
NAME
dbx - dbx symbol table information
DESCRIPTION
The compiler symbol information generated for _d_b_x(1) uses
the same structure as described in _s_t_a_b(5), with additional
type and scope information appended to a symbol's name. The
assembler directive used to describe symbol information has
the following format:
stabs ``_s_t_r_i_n_g'',_k_i_n_d,0,_s_i_z_e,_v_a_l_u_e
_S_t_r_i_n_g contains the name, source language type, and scope of
the symbol, _k_i_n_d specifies the memory class (e.g., external,
static, parameter, local, register), and _s_i_z_e specifies the
byte size of the object, if relevant. The third field (0
above) is unused. For a global variable or a type, _v_a_l_u_e is
unused; for a local variable or parameter, it is the offset
from the frame pointer, for a register variable, it is the
associated register number.
The different kinds of stab entries are interpreted by dbx
as follows:
N_GSYM The symbol is a global variable (e.g., .comm vari-
able). The variable's address can be found from
the corresponding ld(1) symbol entry, thus the
value field for N_GSYM symbols is ignored. For
example, a global variable ``x'' will have both an
N_GSYM entry and an _l_d(1) entry (e.g., N_BSS +
N_EXT). See _a._o_u_t(5) for details about these
other entries. of
N_FUN The symbol is a procedure or function. The size
field contains the line number of the entry point.
The value field contains the address of the entry
point (in the text segment).
N_STSYM The symbol is a statically allocated variable for
which an initial value has been specified. The
value field contains the address of the variable
(in the data segment).
N_LCSYM The symbol is statically allocated, but not ini-
tialized.
N_RSYM The symbol is a register variable whose value is
kept in the register denoted by the value field.
N_PSYM The symbol is a parameter whose value is pushed on
the stack before the call. The value field con-
tains the offset from the argument base pointer
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(on the VAX, the ap register).
N_LSYM The symbol is a local variable whose value is
stored in the most recently defined procedure's
stack frame. The value is the (often negative)
offset from the frame pointer (on the VAX, the fp
register).
N_PC, N_MOD2
The symbol defines separate compilation informa-
tion for pre-linking checking for Berkeley Pascal
and DEC Modula-2 programs respectively. For Pas-
cal, the value field contains the line number that
the symbol is defined on. The value field is not
used for Modula-2.
Most of the source level information about a symbol is
stored in the string field of the stab entry. Since strings
are kept in a separate string table in the a.out file, they
can be arbitrarily long. Thus there are no restrictions on
the kind or length of information in the string field, and
it was not necessary to modify the assembler or loader when
extending or modifying the format of this information.
Below is a grammar describing the syntax of the symbol
string. Except in the case of a constant whose value is a
string, there are no blanks in a symbol string.
NAME: [a-zA-Z_][a-zA-Z_0-9]*
INTEGER: [-][0-9][0-9]*
REAL: [+-][0-9]*(.[0-9][0-9]*|)([eE]([+-]|)[0-9][0-9]*|)
STRING: ``.*''
BSTRING: .*
String:
NAME `:' Class
`:' Class
Class:
`c' `=' Constant `;'
Variable
Procedure
Parameter
NamedType
`X' ExportInfo -- export or import information (for N_MOD2 only)
Constant:
`i' INTEGER
`r' REAL
`c' OrdValue
`b' OrdValue
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`s' STRING
`e' TypeId `,' OrdValue
`S' TypeId `,' NumElements `,' NumBits `,' BSTRING
OrdValue:
INTEGER
NumElements:
INTEGER
NumBits:
INTEGER
Variable:
TypeId -- local variable of type TypeId
`r' TypeId -- register variable of type TypeId
`S' TypeId -- module variable of type TypeId (static global in C)
`V' TypeId -- own variable of type TypeId (static local in C)
`G' TypeId -- global variable of type TypeId
Procedure:
Proc -- top level procedure
Proc `,' NAME `,' NAME -- local to first NAME,
-- second NAME is corresponding ld symbol
Proc:
`P' -- global procedure
`Q' -- local procedure (static in C)
`I' -- internal procedure (different calling sequence)
`F' TypeId -- function returning type TypeId
`f' TypeId -- local function
`J' TypeId -- internal function
Parameter:
`p' TypeId -- value parameter of type TypeId
`v' TypeId -- reference parameter of type TypeId
NamedType:
`t' TypeId -- type name for type TypeId
`T' TypeId -- C structure tag name for struct TypeId
TypeId:
INTEGER -- Unique (per compilation) number of type
INTEGER `=' TypeDef -- Definition of type number
INTEGER `=' TypeAttrs TypeDef
--
-- Type attributes are extra information associated with a type,
-- such as alignment constraints or pointer checking semantics.
-- Dbx interprets some of these, but will ignore rather than complain
-- about any it does not recognize. Therefore this is a way to add
-- extra information for pre-linking checking.
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--
TypeAttrs:
`@' TypeAttrList `;'
TypeAttrList:
TypeAttrList `,' TypeAttr
TypeAttr
TypeAttr:
`a' INTEGER -- align boundary
`s' INTEGER -- size in bits
`p' INTEGER -- pointer class (e.g., checking)
BSTRING -- something else
TypeDef:
INTEGER
Subrange
Array
Record
`e' EnumList `;' -- enumeration
`*' TypeId -- pointer to TypeId
`S' TypeId -- set of TypeId
`d' TypeId -- file of TypeId
ProcedureType
`i' NAME `:' NAME `;' -- imported type ModuleName:Name
`o' NAME `;' -- opaque type
`i' NAME `:' NAME `,' TypeId `;'
`o' NAME `,' TypeId `;'
Subrange:
`r' TypeId `;' INTEGER `;' INTEGER
Array:
`a' TypeId `;' TypeId -- array [TypeId] of TypeId
`A' TypeId -- open array of TypeId
`D' INTEGER `,' TypeId -- N-dim. dynamic array
`E' INTEGER `,' TypeId -- N-dim. subarray
ProcedureType:
`f' TypeId `;' -- C function type
`f' TypeId `,' NumParams `;' TParamList `;'
`p' NumParams `;' TParamList `;'
NumParams:
INTEGER
Record:
`s' ByteSize FieldList `;' -- structure/record
`u' ByteSize FieldList `;' -- C union
ByteSize:
INTEGER
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FieldList :
Field
FieldList Field
Field:
NAME `:' TypeId `,' BitOffset `,' BitSize `;'
BitSize:
INTEGER
BitOffset:
INTEGER
EnumList:
Enum
EnumList Enum
Enum:
NAME `:' OrdValue `,'
ParamList:
Param
ParamList Param
Param:
NAME `:' TypeId `,' PassBy `;'
PassBy:
INTEGER
TParam:
TypeId `,' PassBy `;'
TParamList :
TParam
TParamList TParam
Export:
INTEGER ExportInfo
ExportInfo:
`t' TypeId
`f' TypeId `,' NumParams `;' ParamList `;'
`p' NumParams `;' ParamList `;'
`v' TypeId
`c' `=' Constant
A `?' indicates that the symbol information is continued in
the next stab entry. This directive can only occur where a
`;' would otherwise separate the fields of a record or con-
stants in an enumeration. It is useful when the number of
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DBX(5) UNIX Programmer's Manual DBX(5)
elements in one of these lists is large.
SEE ALSO
dbx(1), stab(5), a.out(5)
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