diff options
Diffstat (limited to 'gdb/doc')
| -rw-r--r-- | gdb/doc/ChangeLog | 4 | ||||
| -rw-r--r-- | gdb/doc/stabs.texinfo | 154 |
2 files changed, 57 insertions, 101 deletions
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index f9e4d05..0abd09c 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,7 @@ +Tue Aug 17 15:57:27 1993 Jim Kingdon (kingdon@lioth.cygnus.com) + + * stabs.texinfo (Stack Variables): Re-write. + Mon Aug 16 21:20:08 1993 Jim Kingdon (kingdon@lioth.cygnus.com) * stabs.texinfo (Stabs-in-elf): Talk about getting the start diff --git a/gdb/doc/stabs.texinfo b/gdb/doc/stabs.texinfo index 1c80bf4..39b0872 100644 --- a/gdb/doc/stabs.texinfo +++ b/gdb/doc/stabs.texinfo @@ -218,21 +218,21 @@ descriptors}. The @samp{c} symbol descriptor is an exception in that it is not followed by type information. @xref{Constants}. -Type information is either a @var{type_number}, or a +Type information is either a @var{type_number}, or @samp{@var{type_number}=}. The @var{type_number} alone is a type reference, referring directly to a type that has already been defined. -The @samp{@var{type_number}=} is a type definition, where the number -represents a new type which is about to be defined. The type definition -may refer to other types by number, and those type numbers may be -followed by @samp{=} and nested definitions. +The @samp{@var{type_number}=} form is a type definition, where the +number represents a new type which is about to be defined. The type +definition may refer to other types by number, and those type numbers +may be followed by @samp{=} and nested definitions. In a type definition, if the character that follows the equals sign is non-numeric then it is a @var{type_descriptor}, and tells what kind of type is about to be defined. Any other values following the @var{type_descriptor} vary, depending on the @var{type_descriptor}. If a number follows the @samp{=} then the number is a @var{type_reference}. -This is described more thoroughly in the section on types. @xref{Type +For a full description of types, @ref{Types}. @xref{Type Descriptors,,Table D: Type Descriptors}, for a list of @var{type_descriptor} values. @@ -840,7 +840,7 @@ nesting is reflected in the nested bracketing stabs (@code{N_LBRAC}, @chapter Variables @menu -* Automatic variables:: Variables allocated on the stack. +* Stack Variables:: Variables allocated on the stack. * Global Variables:: Variables used by more than one source file. * Register variables:: Variables in registers. * Common Blocks:: Variables statically allocated together. @@ -848,70 +848,54 @@ nesting is reflected in the nested bracketing stabs (@code{N_LBRAC}, * Parameters:: Variables for arguments to functions. @end menu -@node Automatic variables -@section Locally scoped automatic variables +@node Stack Variables +@section Automatic Variables Allocated on the Stack -@table @strong -@item Directive: -@code{.stabs} -@item Type: -@code{N_LSYM} -@item Symbol Descriptor: -none -@end table +If a variable is declared whose scope is local to a function and whose +lifetime is only as long as that function executes (C calls such +variables automatic), they can be allocated in a register +(@pxref{Register variables}) or on the stack. -In addition to describing types, the @code{N_LSYM} stab type also -describes locally scoped automatic variables. Refer again to the body -of @code{main} in @file{example2.c}. It allocates two automatic -variables: @samp{times} is scoped to the body of @code{main}, and -@samp{inner} is scoped to the body of the @code{for} loop. -@samp{s_flap} is locally scoped but not automatic, and will be discussed -later. +For variables allocated on the stack, each variable has a stab with the +symbol descriptor omitted. Since type information should being with a +digit, @samp{-}, or @samp{(}, only digits, @samp{-}, and @samp{(} are +precluded from being used for symbol descriptors by this fact. However, +the Acorn RISC machine (ARM) is said to get this wrong: it puts out a +mere type definition here, without the preceding +@code{@var{typenumber}=}. This is a bad idea; there is no guarantee +that type descriptors are distinct from symbol descriptors. -@example -20 @{ -21 static float s_flap; -22 int times; -23 for (times=0; times < s_g_repeat; times++)@{ -24 int inner; -25 printf ("Hello world\n"); -26 @} -27 @}; -@end example +These stabs have the @code{N_LSYM} stab type. The value of the stab is +the offset of the variable within the local variables. On most machines +this is an offset from the frame pointer and is negative. -The @code{N_LSYM} stab for an automatic variable is located just before the -@code{N_LBRAC} stab describing the open brace of the block to which it is -scoped. +The stab for an automatic variable is located just before the +@code{N_LBRAC} stab describing the open brace of the block to which it +is scoped, except for some compilers which put the automatic variables +after the @code{N_LBRAC} (see @code{VARIABLES_INSIDE_BLOCK} in GDB). -@example -@exdent @code{N_LSYM} (128): automatic variable, scoped locally to @code{main} - -.stabs "@var{name}: - @var{type information}", - N_LSYM, NIL, NIL, - @var{frame-pointer-offset} +For example, the following C code -98 .stabs "times:1",128,0,0,-20 -99 .stabn 192,0,0,LBB2 ## begin `main' N_LBRAC - -@exdent @code{N_LSYM} (128): automatic variable, scoped locally to the @code{for} loop +@example +int +main () +@{ + int x; +@} +@end example -.stabs "@var{name}: - @var{type information}", - N_LSYM, NIL, NIL, - @var{frame-pointer-offset} +produces the following stabs -100 .stabs "inner:1",128,0,0,-24 -101 .stabn 192,0,0,LBB3 ## begin `for' loop N_LBRAC +@example +.stabs "main:F1",36,0,0,_main # N_FUN +.stabs "x:1",128,0,0,-12 # N_LSYM +.stabn 192,0,0,LBB2 # N_LBRAC +.stabn 224,0,0,LBE2 # N_RBRAC @end example -The symbol descriptor is omitted for automatic variables. Since type -information should being with a digit, @samp{-}, or @samp{(}, only -digits, @samp{-}, and @samp{(} are precluded from being used for symbol -descriptors by this fact. However, the Acorn RISC machine (ARM) is said -to get this wrong: it puts out a mere type definition here, without the -preceding @code{@var{typenumber}=}. This is a bad idea; there is no -guarantee that type descriptors are distinct from symbol descriptors. +@xref{Procedures} for more information on the @samp{F} symbol desciptor, +and @ref{Block Structure} for more information on the @code{N_LBRAC} and +@code{N_RBRAC} symbols. @node Global Variables @section Global Variables @@ -1861,9 +1845,11 @@ element of. So the definition of structure type 16 contains an type definition for an element which is a pointer to type 16. @node Typedefs -@section Giving a type a name +@section Giving a Type a Name -To give a type a name, use the @samp{t} symbol descriptor. For example, +To give a type a name, use the @samp{t} symbol descriptor. The type +specified by the type information (@pxref{Stabs Format}) for the stab. +For example, @example .stabs "s_typedef:t16",128,0,0,0 @@ -1883,7 +1869,7 @@ means---is it always the same as the name of the type, or is this type descriptor used with a nameless stab (@pxref{Stabs Format})? There optionally follows a comma followed by type information which defines the type of this type. If omitted, a semicolon is used in place of the -comma and the type information, and, the type is much like a generic +comma and the type information, and the type is much like a generic pointer type---it has a known size but little else about it is specified. @@ -1937,8 +1923,7 @@ After that is a list of union element descriptions. Their format is name:type, bit offset into the union, and number of bytes for the element;. -The stab for the union variable follows. Notice that the frame -pointer offset for local variables is negative. +The stab for the union variable follows. @display <128> N_LSYM - local variable (with no symbol descriptor) @@ -3106,7 +3091,7 @@ Last stab for module (Solaris2). Path and name of source file, @xref{Source Files}. @item 0x80 N_LSYM -Stack variable or type definition, @xref{N_LSYM}, @xref{Typedefs}. +Stack variable (@pxref{Stack Variables}) or type (@pxref{Typedefs}). @item 0x82 N_BINCL Beginning of an include file (Sun only), @xref{Source Files}. @@ -3181,7 +3166,7 @@ Gould non-base registers, @xref{Gould}. @item @var{digit} @itemx ( @itemx - -Local variable, @xref{Automatic variables}. +Variable on the stack, @xref{Stack Variables}. @item a Parameter passed by reference in register, @xref{Parameters}. @@ -3440,7 +3425,6 @@ Finally, any further information. * N_MOD2:: Modula2 information "for imc" * N_CATCH:: GNU C++ "catch" clause * N_SSYM:: Structure or union element -* N_LSYM:: Automatic variable * N_ENTRY:: Alternate entry point * N_SCOPE:: Modula2 scope information (Sun only) * Gould:: non-base register symbols used on Gould systems @@ -3589,38 +3573,6 @@ Value is offset in the structure. <<?looking at structs and unions in C I didn't see these>> -@node N_LSYM -@section 128 - 0x80 - N_LSYM -Automatic var in the stack (also used for type descriptors.) - -@display -.stabs "name" N_LSYM, NIL, NIL, value -@end display - -@example -@exdent @emph{For stack based local variables:} - -"name" -> name of the variable -value -> offset from frame pointer (negative) - -@exdent @emph{For type descriptors:} - -"name" -> "name_of_the_type:#type" - # -> t - -type -> type_ref (or) type_def - -type_ref -> type_number -type_def -> type_number=type_desc etc. -@end example - -Type may be either a type reference or a type definition. A type -reference is a number that refers to a previously defined type. A -type definition is the number that will refer to this type, followed -by an equals sign, a type descriptor and the additional data that -defines the type. See the Table D for type descriptors and the -section on types for what data follows each type descriptor. - @node N_ENTRY @section 164 - 0xa4 - N_ENTRY |