Subversion Repositories openrisc_2011-10-31

/* Symbol table definitions for GDB.

   Copyright (C) 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,

   1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2007, 2008, 2009, 2010

   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#if !defined (SYMTAB_H)

#define SYMTAB_H 1

/* Opaque declarations.  */

struct ui_file;

struct frame_info;

struct symbol;

struct obstack;

struct objfile;

struct block;

struct blockvector;

struct axs_value;

struct agent_expr;

struct program_space;

/* Some of the structures in this file are space critical.

   The space-critical structures are:

     struct general_symbol_info

     struct symbol

     struct partial_symbol

   These structures are laid out to encourage good packing.

   They use ENUM_BITFIELD and short int fields, and they order the

   structure members so that fields less than a word are next

   to each other so they can be packed together. */

/* Rearranged: used ENUM_BITFIELD and rearranged field order in

   all the space critical structures (plus struct minimal_symbol).

   Memory usage dropped from 99360768 bytes to 90001408 bytes.

   I measured this with before-and-after tests of

   "HEAD-old-gdb -readnow HEAD-old-gdb" and

   "HEAD-new-gdb -readnow HEAD-old-gdb" on native i686-pc-linux-gnu,

   red hat linux 8, with LD_LIBRARY_PATH=/usr/lib/debug,

   typing "maint space 1" at the first command prompt.

   Here is another measurement (from andrew c):

     # no /usr/lib/debug, just plain glibc, like a normal user

     gdb HEAD-old-gdb

     (gdb) break internal_error

     (gdb) run

     (gdb) maint internal-error

     (gdb) backtrace

     (gdb) maint space 1

   gdb gdb_6_0_branch  2003-08-19  space used: 8896512

   gdb HEAD            2003-08-19  space used: 8904704

   gdb HEAD            2003-08-21  space used: 8396800 (+symtab.h)

   gdb HEAD            2003-08-21  space used: 8265728 (+gdbtypes.h)

   The third line shows the savings from the optimizations in symtab.h.

   The fourth line shows the savings from the optimizations in

   gdbtypes.h.  Both optimizations are in gdb HEAD now.

   --chastain 2003-08-21  */

/* Define a structure for the information that is common to all symbol types,

   including minimal symbols, partial symbols, and full symbols.  In a

   multilanguage environment, some language specific information may need to

   be recorded along with each symbol. */

/* This structure is space critical.  See space comments at the top. */

struct general_symbol_info

{

  /* Name of the symbol.  This is a required field.  Storage for the

     name is allocated on the objfile_obstack for the associated

     objfile.  For languages like C++ that make a distinction between

     the mangled name and demangled name, this is the mangled

     name.  */

  char *name;

  /* Value of the symbol.  Which member of this union to use, and what

     it means, depends on what kind of symbol this is and its

     SYMBOL_CLASS.  See comments there for more details.  All of these

     are in host byte order (though what they point to might be in

     target byte order, e.g. LOC_CONST_BYTES).  */

  union

  {

    /* The fact that this is a long not a LONGEST mainly limits the

       range of a LOC_CONST.  Since LOC_CONST_BYTES exists, I'm not

       sure that is a big deal.  */

    long ivalue;

    struct block *block;

    gdb_byte *bytes;

    CORE_ADDR address;

    /* for opaque typedef struct chain */

    struct symbol *chain;

  }

  value;

  /* Since one and only one language can apply, wrap the language specific

     information inside a union. */

  union

  {

    struct cplus_specific

    {

      /* This is in fact used for C++, Java, and Objective C.  */

      char *demangled_name;

    }

    cplus_specific;

  }

  language_specific;

  /* Record the source code language that applies to this symbol.

     This is used to select one of the fields from the language specific

     union above. */

  ENUM_BITFIELD(language) language : 8;

  /* Which section is this symbol in?  This is an index into

     section_offsets for this objfile.  Negative means that the symbol

     does not get relocated relative to a section.

     Disclaimer: currently this is just used for xcoff, so don't

     expect all symbol-reading code to set it correctly (the ELF code

     also tries to set it correctly).  */

  short section;

  /* The section associated with this symbol. */

  struct obj_section *obj_section;

};

extern CORE_ADDR symbol_overlayed_address (CORE_ADDR, struct obj_section *);

/* Note that all the following SYMBOL_* macros are used with the

   SYMBOL argument being either a partial symbol, a minimal symbol or

   a full symbol.  All three types have a ginfo field.  In particular

   the SYMBOL_INIT_LANGUAGE_SPECIFIC, SYMBOL_DEMANGLED_NAME, etc.

   macros cannot be entirely substituted by

   functions, unless the callers are changed to pass in the ginfo

   field only, instead of the SYMBOL parameter.  */

#define SYMBOL_VALUE(symbol)            (symbol)->ginfo.value.ivalue

#define SYMBOL_VALUE_ADDRESS(symbol)    (symbol)->ginfo.value.address

#define SYMBOL_VALUE_BYTES(symbol)      (symbol)->ginfo.value.bytes

#define SYMBOL_BLOCK_VALUE(symbol)      (symbol)->ginfo.value.block

#define SYMBOL_VALUE_CHAIN(symbol)      (symbol)->ginfo.value.chain

#define SYMBOL_LANGUAGE(symbol)         (symbol)->ginfo.language

#define SYMBOL_SECTION(symbol)          (symbol)->ginfo.section

#define SYMBOL_OBJ_SECTION(symbol)      (symbol)->ginfo.obj_section

#define SYMBOL_CPLUS_DEMANGLED_NAME(symbol)     \

  (symbol)->ginfo.language_specific.cplus_specific.demangled_name

/* Initializes the language dependent portion of a symbol

   depending upon the language for the symbol. */

#define SYMBOL_INIT_LANGUAGE_SPECIFIC(symbol,language) \

  (symbol_init_language_specific (&(symbol)->ginfo, (language)))

extern void symbol_init_language_specific (struct general_symbol_info *symbol,

                                           enum language language);

/* Set just the linkage name of a symbol; do not try to demangle

   it.  Used for constructs which do not have a mangled name,

   e.g. struct tags.  Unlike SYMBOL_SET_NAMES, linkage_name must

   be terminated and either already on the objfile's obstack or

   permanently allocated.  */

#define SYMBOL_SET_LINKAGE_NAME(symbol,linkage_name) \

  (symbol)->ginfo.name = (linkage_name)

/* Set the linkage and natural names of a symbol, by demangling

   the linkage name.  */

#define SYMBOL_SET_NAMES(symbol,linkage_name,len,copy_name,objfile)     \

  symbol_set_names (&(symbol)->ginfo, linkage_name, len, copy_name, objfile)

extern void symbol_set_names (struct general_symbol_info *symbol,

                              const char *linkage_name, int len, int copy_name,

                              struct objfile *objfile);

/* Now come lots of name accessor macros.  Short version as to when to

   use which: Use SYMBOL_NATURAL_NAME to refer to the name of the

   symbol in the original source code.  Use SYMBOL_LINKAGE_NAME if you

   want to know what the linker thinks the symbol's name is.  Use

   SYMBOL_PRINT_NAME for output.  Use SYMBOL_DEMANGLED_NAME if you

   specifically need to know whether SYMBOL_NATURAL_NAME and

   SYMBOL_LINKAGE_NAME are different.  */

/* Return SYMBOL's "natural" name, i.e. the name that it was called in

   the original source code.  In languages like C++ where symbols may

   be mangled for ease of manipulation by the linker, this is the

   demangled name.  */

#define SYMBOL_NATURAL_NAME(symbol) \

  (symbol_natural_name (&(symbol)->ginfo))

extern char *symbol_natural_name (const struct general_symbol_info *symbol);

/* Return SYMBOL's name from the point of view of the linker.  In

   languages like C++ where symbols may be mangled for ease of

   manipulation by the linker, this is the mangled name; otherwise,

   it's the same as SYMBOL_NATURAL_NAME.  */

#define SYMBOL_LINKAGE_NAME(symbol)     (symbol)->ginfo.name

/* Return the demangled name for a symbol based on the language for

   that symbol.  If no demangled name exists, return NULL. */

#define SYMBOL_DEMANGLED_NAME(symbol) \

  (symbol_demangled_name (&(symbol)->ginfo))

extern char *symbol_demangled_name (const struct general_symbol_info *symbol);

/* Macro that returns a version of the name of a symbol that is

   suitable for output.  In C++ this is the "demangled" form of the

   name if demangle is on and the "mangled" form of the name if

   demangle is off.  In other languages this is just the symbol name.

   The result should never be NULL.  Don't use this for internal

   purposes (e.g. storing in a hashtable): it's only suitable for

   output.  */

#define SYMBOL_PRINT_NAME(symbol)                                       \

  (demangle ? SYMBOL_NATURAL_NAME (symbol) : SYMBOL_LINKAGE_NAME (symbol))

/* Macro that tests a symbol for a match against a specified name string.

   First test the unencoded name, then looks for and test a C++ encoded

   name if it exists.  Note that whitespace is ignored while attempting to

   match a C++ encoded name, so that "foo::bar(int,long)" is the same as

   "foo :: bar (int, long)".

   Evaluates to zero if the match fails, or nonzero if it succeeds. */

/* Macro that tests a symbol for a match against a specified name

   string.  It tests against SYMBOL_NATURAL_NAME, and it ignores

   whitespace and trailing parentheses.  (See strcmp_iw for details

   about its behavior.)  */

#define SYMBOL_MATCHES_NATURAL_NAME(symbol, name)                       \

  (strcmp_iw (SYMBOL_NATURAL_NAME (symbol), (name)) == 0)

/* Macro that returns the name to be used when sorting and searching symbols.

   In  C++, Chill, and Java, we search for the demangled form of a name,

   and so sort symbols accordingly.  In Ada, however, we search by mangled

   name.  If there is no distinct demangled name, then SYMBOL_SEARCH_NAME

   returns the same value (same pointer) as SYMBOL_LINKAGE_NAME. */

#define SYMBOL_SEARCH_NAME(symbol)                                       \

   (symbol_search_name (&(symbol)->ginfo))

extern char *symbol_search_name (const struct general_symbol_info *);

/* Analogous to SYMBOL_MATCHES_NATURAL_NAME, but uses the search

   name.  */

#define SYMBOL_MATCHES_SEARCH_NAME(symbol, name)                        \

  (strcmp_iw (SYMBOL_SEARCH_NAME (symbol), (name)) == 0)

/* Classification types for a minimal symbol.  These should be taken as

   "advisory only", since if gdb can't easily figure out a

   classification it simply selects mst_unknown.  It may also have to

   guess when it can't figure out which is a better match between two

   types (mst_data versus mst_bss) for example.  Since the minimal

   symbol info is sometimes derived from the BFD library's view of a

   file, we need to live with what information bfd supplies. */

enum minimal_symbol_type

{

  mst_unknown = 0,               /* Unknown type, the default */

  mst_text,                     /* Generally executable instructions */

  mst_data,                     /* Generally initialized data */

  mst_bss,                      /* Generally uninitialized data */

  mst_abs,                      /* Generally absolute (nonrelocatable) */

  /* GDB uses mst_solib_trampoline for the start address of a shared

     library trampoline entry.  Breakpoints for shared library functions

     are put there if the shared library is not yet loaded.

     After the shared library is loaded, lookup_minimal_symbol will

     prefer the minimal symbol from the shared library (usually

     a mst_text symbol) over the mst_solib_trampoline symbol, and the

     breakpoints will be moved to their true address in the shared

     library via breakpoint_re_set.  */

  mst_solib_trampoline,         /* Shared library trampoline code */

  /* For the mst_file* types, the names are only guaranteed to be unique

     within a given .o file.  */

  mst_file_text,                /* Static version of mst_text */

  mst_file_data,                /* Static version of mst_data */

  mst_file_bss                  /* Static version of mst_bss */

};

/* Define a simple structure used to hold some very basic information about

   all defined global symbols (text, data, bss, abs, etc).  The only required

   information is the general_symbol_info.

   In many cases, even if a file was compiled with no special options for

   debugging at all, as long as was not stripped it will contain sufficient

   information to build a useful minimal symbol table using this structure.

   Even when a file contains enough debugging information to build a full

   symbol table, these minimal symbols are still useful for quickly mapping

   between names and addresses, and vice versa.  They are also sometimes

   used to figure out what full symbol table entries need to be read in. */

struct minimal_symbol

{

  /* The general symbol info required for all types of symbols.

     The SYMBOL_VALUE_ADDRESS contains the address that this symbol

     corresponds to.  */

  struct general_symbol_info ginfo;

  /* Size of this symbol.  end_psymtab in dbxread.c uses this

     information to calculate the end of the partial symtab based on the

     address of the last symbol plus the size of the last symbol.  */

  unsigned long size;

  /* Which source file is this symbol in?  Only relevant for mst_file_*.  */

  char *filename;

  /* Classification type for this minimal symbol.  */

  ENUM_BITFIELD(minimal_symbol_type) type : 8;

  /* Two flag bits provided for the use of the target.  */

  unsigned int target_flag_1 : 1;

  unsigned int target_flag_2 : 1;

  /* Minimal symbols with the same hash key are kept on a linked

     list.  This is the link.  */

  struct minimal_symbol *hash_next;

  /* Minimal symbols are stored in two different hash tables.  This is

     the `next' pointer for the demangled hash table.  */

  struct minimal_symbol *demangled_hash_next;

};

#define MSYMBOL_TARGET_FLAG_1(msymbol)  (msymbol)->target_flag_1

#define MSYMBOL_TARGET_FLAG_2(msymbol)  (msymbol)->target_flag_2

#define MSYMBOL_SIZE(msymbol)           (msymbol)->size

#define MSYMBOL_TYPE(msymbol)           (msymbol)->type

/* Represent one symbol name; a variable, constant, function or typedef.  */

/* Different name domains for symbols.  Looking up a symbol specifies a

   domain and ignores symbol definitions in other name domains. */

typedef enum domain_enum_tag

{

  /* UNDEF_DOMAIN is used when a domain has not been discovered or

     none of the following apply.  This usually indicates an error either

     in the symbol information or in gdb's handling of symbols. */

  UNDEF_DOMAIN,

  /* VAR_DOMAIN is the usual domain.  In C, this contains variables,

     function names, typedef names and enum type values. */

  VAR_DOMAIN,

  /* STRUCT_DOMAIN is used in C to hold struct, union and enum type names.

     Thus, if `struct foo' is used in a C program, it produces a symbol named

     `foo' in the STRUCT_DOMAIN. */

  STRUCT_DOMAIN,

  /* LABEL_DOMAIN may be used for names of labels (for gotos);

     currently it is not used and labels are not recorded at all.  */

  LABEL_DOMAIN,

  /* Searching domains. These overlap with VAR_DOMAIN, providing

     some granularity with the search_symbols function. */

  /* Everything in VAR_DOMAIN minus FUNCTIONS_DOMAIN and

     TYPES_DOMAIN.  */

  VARIABLES_DOMAIN,

  /* All functions -- for some reason not methods, though. */

  FUNCTIONS_DOMAIN,

  /* All defined types */

  TYPES_DOMAIN

}

domain_enum;

/* An address-class says where to find the value of a symbol.  */

enum address_class

{

  /* Not used; catches errors */

  LOC_UNDEF,

  /* Value is constant int SYMBOL_VALUE, host byteorder */

  LOC_CONST,

  /* Value is at fixed address SYMBOL_VALUE_ADDRESS */

  LOC_STATIC,

  /* Value is in register.  SYMBOL_VALUE is the register number

     in the original debug format.  SYMBOL_REGISTER_OPS holds a

     function that can be called to transform this into the

     actual register number this represents in a specific target

     architecture (gdbarch).

     For some symbol formats (stabs, for some compilers at least),

     the compiler generates two symbols, an argument and a register.

     In some cases we combine them to a single LOC_REGISTER in symbol

     reading, but currently not for all cases (e.g. it's passed on the

     stack and then loaded into a register).  */

  LOC_REGISTER,

  /* It's an argument; the value is at SYMBOL_VALUE offset in arglist.  */

  LOC_ARG,

  /* Value address is at SYMBOL_VALUE offset in arglist.  */

  LOC_REF_ARG,

  /* Value is in specified register.  Just like LOC_REGISTER except the

     register holds the address of the argument instead of the argument

     itself. This is currently used for the passing of structs and unions

     on sparc and hppa.  It is also used for call by reference where the

     address is in a register, at least by mipsread.c.  */

  LOC_REGPARM_ADDR,

  /* Value is a local variable at SYMBOL_VALUE offset in stack frame.  */

  LOC_LOCAL,

  /* Value not used; definition in SYMBOL_TYPE.  Symbols in the domain

     STRUCT_DOMAIN all have this class.  */

  LOC_TYPEDEF,

  /* Value is address SYMBOL_VALUE_ADDRESS in the code */

  LOC_LABEL,

  /* In a symbol table, value is SYMBOL_BLOCK_VALUE of a `struct block'.

     In a partial symbol table, SYMBOL_VALUE_ADDRESS is the start address

     of the block.  Function names have this class. */

  LOC_BLOCK,

  /* Value is a constant byte-sequence pointed to by SYMBOL_VALUE_BYTES, in

     target byte order.  */

  LOC_CONST_BYTES,

  /* Value is at fixed address, but the address of the variable has

     to be determined from the minimal symbol table whenever the

     variable is referenced.

     This happens if debugging information for a global symbol is

     emitted and the corresponding minimal symbol is defined

     in another object file or runtime common storage.

     The linker might even remove the minimal symbol if the global

     symbol is never referenced, in which case the symbol remains

     unresolved.

     GDB would normally find the symbol in the minimal symbol table if it will

     not find it in the full symbol table.  But a reference to an external

     symbol in a local block shadowing other definition requires full symbol

     without possibly having its address available for LOC_STATIC.  Testcase

     is provided as `gdb.dwarf2/dw2-unresolved.exp'.  */

  LOC_UNRESOLVED,

  /* The variable does not actually exist in the program.

     The value is ignored.  */

  LOC_OPTIMIZED_OUT,

  /* The variable's address is computed by a set of location

     functions (see "struct symbol_computed_ops" below).  */

  LOC_COMPUTED,

};

/* The methods needed to implement LOC_COMPUTED.  These methods can

   use the symbol's .aux_value for additional per-symbol information.

   At present this is only used to implement location expressions.  */

struct symbol_computed_ops

{

  /* Return the value of the variable SYMBOL, relative to the stack

     frame FRAME.  If the variable has been optimized out, return

     zero.

     Iff `read_needs_frame (SYMBOL)' is zero, then FRAME may be zero.  */

  struct value *(*read_variable) (struct symbol * symbol,

                                  struct frame_info * frame);

  /* Return non-zero if we need a frame to find the value of the SYMBOL.  */

  int (*read_needs_frame) (struct symbol * symbol);

  /* Write to STREAM a natural-language description of the location of

     SYMBOL.  */

  int (*describe_location) (struct symbol * symbol, struct ui_file * stream);

  /* Tracepoint support.  Append bytecodes to the tracepoint agent

     expression AX that push the address of the object SYMBOL.  Set

     VALUE appropriately.  Note --- for objects in registers, this

     needn't emit any code; as long as it sets VALUE properly, then

     the caller will generate the right code in the process of

     treating this as an lvalue or rvalue.  */

  void (*tracepoint_var_ref) (struct symbol *symbol, struct gdbarch *gdbarch,

                              struct agent_expr *ax, struct axs_value *value);

};

/* Functions used with LOC_REGISTER and LOC_REGPARM_ADDR.  */

struct symbol_register_ops

{

  int (*register_number) (struct symbol *symbol, struct gdbarch *gdbarch);

};

/* This structure is space critical.  See space comments at the top. */

struct symbol

{

  /* The general symbol info required for all types of symbols. */

  struct general_symbol_info ginfo;

  /* Data type of value */

  struct type *type;

  /* The symbol table containing this symbol.  This is the file

     associated with LINE.  It can be NULL during symbols read-in but it is

     never NULL during normal operation.  */

  struct symtab *symtab;

  /* Domain code.  */

  ENUM_BITFIELD(domain_enum_tag) domain : 6;

  /* Address class */

  /* NOTE: cagney/2003-11-02: The fields "aclass" and "ops" contain

     overlapping information.  By creating a per-aclass ops vector, or

     using the aclass as an index into an ops table, the aclass and

     ops fields can be merged.  The latter, for instance, would shave

     32-bits from each symbol (relative to a symbol lookup, any table

     index overhead would be in the noise).  */

  ENUM_BITFIELD(address_class) aclass : 6;

  /* Whether this is an argument.  */

  unsigned is_argument : 1;

  /* Whether this is an inlined function (class LOC_BLOCK only).  */

  unsigned is_inlined : 1;

  /* Line number of this symbol's definition, except for inlined

     functions.  For an inlined function (class LOC_BLOCK and

     SYMBOL_INLINED set) this is the line number of the function's call

     site.  Inlined function symbols are not definitions, and they are

     never found by symbol table lookup.

     FIXME: Should we really make the assumption that nobody will try

     to debug files longer than 64K lines?  What about machine

     generated programs?  */

  unsigned short line;

  /* Method's for symbol's of this class.  */

  /* NOTE: cagney/2003-11-02: See comment above attached to "aclass".  */

  union

    {

      /* Used with LOC_COMPUTED.  */

      const struct symbol_computed_ops *ops_computed;

      /* Used with LOC_REGISTER and LOC_REGPARM_ADDR.  */

      const struct symbol_register_ops *ops_register;

    } ops;

  /* An arbitrary data pointer, allowing symbol readers to record

     additional information on a per-symbol basis.  Note that this data

     must be allocated using the same obstack as the symbol itself.  */

  /* So far it is only used by LOC_COMPUTED to

     find the location information.  For a LOC_BLOCK symbol

     for a function in a compilation unit compiled with DWARF 2

     information, this is information used internally by the DWARF 2

     code --- specifically, the location expression for the frame

     base for this function.  */

  /* FIXME drow/2003-02-21: For the LOC_BLOCK case, it might be better

     to add a magic symbol to the block containing this information,

     or to have a generic debug info annotation slot for symbols.  */

  void *aux_value;

  struct symbol *hash_next;

};

#define SYMBOL_DOMAIN(symbol)   (symbol)->domain

#define SYMBOL_CLASS(symbol)            (symbol)->aclass

#define SYMBOL_IS_ARGUMENT(symbol)      (symbol)->is_argument

#define SYMBOL_INLINED(symbol)          (symbol)->is_inlined

#define SYMBOL_TYPE(symbol)             (symbol)->type

#define SYMBOL_LINE(symbol)             (symbol)->line

#define SYMBOL_SYMTAB(symbol)           (symbol)->symtab

#define SYMBOL_COMPUTED_OPS(symbol)     (symbol)->ops.ops_computed

#define SYMBOL_REGISTER_OPS(symbol)     (symbol)->ops.ops_register

#define SYMBOL_LOCATION_BATON(symbol)   (symbol)->aux_value

/* A partial_symbol records the name, domain, and address class of

   symbols whose types we have not parsed yet.  For functions, it also

   contains their memory address, so we can find them from a PC value.

   Each partial_symbol sits in a partial_symtab, all of which are chained

   on a  partial symtab list and which points to the corresponding

   normal symtab once the partial_symtab has been referenced.  */

/* This structure is space critical.  See space comments at the top. */

struct partial_symbol

{

  /* The general symbol info required for all types of symbols. */

  struct general_symbol_info ginfo;

  /* Name space code.  */

  ENUM_BITFIELD(domain_enum_tag) domain : 6;

  /* Address class (for info_symbols) */

  ENUM_BITFIELD(address_class) aclass : 6;

};

#define PSYMBOL_DOMAIN(psymbol) (psymbol)->domain

#define PSYMBOL_CLASS(psymbol)          (psymbol)->aclass

/* Each item represents a line-->pc (or the reverse) mapping.  This is

   somewhat more wasteful of space than one might wish, but since only

   the files which are actually debugged are read in to core, we don't

   waste much space.  */

struct linetable_entry

{

  int line;

  CORE_ADDR pc;

};

/* The order of entries in the linetable is significant.  They should

   be sorted by increasing values of the pc field.  If there is more than

   one entry for a given pc, then I'm not sure what should happen (and

   I not sure whether we currently handle it the best way).

   Example: a C for statement generally looks like this

   10   0x100   - for the init/test part of a for stmt.

   20   0x200

   30   0x300

   10   0x400   - for the increment part of a for stmt.

   If an entry has a line number of zero, it marks the start of a PC

   range for which no line number information is available.  It is

   acceptable, though wasteful of table space, for such a range to be

   zero length.  */

struct linetable

{

  int nitems;

  /* Actually NITEMS elements.  If you don't like this use of the

     `struct hack', you can shove it up your ANSI (seriously, if the

     committee tells us how to do it, we can probably go along).  */

  struct linetable_entry item[1];

};

/* How to relocate the symbols from each section in a symbol file.

   Each struct contains an array of offsets.

   The ordering and meaning of the offsets is file-type-dependent;

   typically it is indexed by section numbers or symbol types or

   something like that.

   To give us flexibility in changing the internal representation

   of these offsets, the ANOFFSET macro must be used to insert and

   extract offset values in the struct.  */

struct section_offsets

{

  CORE_ADDR offsets[1];         /* As many as needed. */

};

#define ANOFFSET(secoff, whichone) \

   ((whichone == -1) \

    ? (internal_error (__FILE__, __LINE__, _("Section index is uninitialized")), -1) \

    : secoff->offsets[whichone])

/* The size of a section_offsets table for N sections.  */

#define SIZEOF_N_SECTION_OFFSETS(n) \

  (sizeof (struct section_offsets) \

   + sizeof (((struct section_offsets *) 0)->offsets) * ((n)-1))

/* Each source file or header is represented by a struct symtab.

   These objects are chained through the `next' field.  */

struct symtab

{

  /* Chain of all existing symtabs.  */

  struct symtab *next;

  /* List of all symbol scope blocks for this symtab.  May be shared

     between different symtabs (and normally is for all the symtabs

     in a given compilation unit).  */

  struct blockvector *blockvector;

  /* Table mapping core addresses to line numbers for this file.

     Can be NULL if none.  Never shared between different symtabs.  */

  struct linetable *linetable;

  /* Section in objfile->section_offsets for the blockvector and

     the linetable.  Probably always SECT_OFF_TEXT.  */

  int block_line_section;

  /* If several symtabs share a blockvector, exactly one of them

     should be designated the primary, so that the blockvector

     is relocated exactly once by objfile_relocate.  */

  int primary;

  /* The macro table for this symtab.  Like the blockvector, this

     may be shared between different symtabs --- and normally is for

     all the symtabs in a given compilation unit.  */

  struct macro_table *macro_table;

  /* Name of this source file.  */

  char *filename;

  /* Directory in which it was compiled, or NULL if we don't know.  */

  char *dirname;

  /* This component says how to free the data we point to:

     free_nothing => do nothing; some other symtab will free

     the data this one uses.

     free_linetable => free just the linetable.  FIXME: Is this redundant

     with the primary field?  */

  enum free_code

  {

    free_nothing, free_linetable

  }

  free_code;

  /* A function to call to free space, if necessary.  This is IN

     ADDITION to the action indicated by free_code.  */

  void (*free_func)(struct symtab *symtab);

  /* Total number of lines found in source file.  */

  int nlines;

  /* line_charpos[N] is the position of the (N-1)th line of the

     source file.  "position" means something we can lseek() to; it

     is not guaranteed to be useful any other way.  */

  int *line_charpos;

  /* Language of this source file.  */

  enum language language;

  /* String that identifies the format of the debugging information, such

     as "stabs", "dwarf 1", "dwarf 2", "coff", etc.  This is mostly useful

     for automated testing of gdb but may also be information that is

     useful to the user. */

  char *debugformat;

  /* String of producer version information.  May be zero.  */

  char *producer;

  /* Full name of file as found by searching the source path.

     NULL if not yet known.  */

  char *fullname;

  /* Object file from which this symbol information was read.  */

  struct objfile *objfile;

};

#define BLOCKVECTOR(symtab)     (symtab)->blockvector

#define LINETABLE(symtab)       (symtab)->linetable

#define SYMTAB_PSPACE(symtab)   (symtab)->objfile->pspace

/* Each source file that has not been fully read in is represented by

   a partial_symtab.  This contains the information on where in the

   executable the debugging symbols for a specific file are, and a

   list of names of global symbols which are located in this file.