old-cross-binutils/gdb/guile
Pierre-Marie de Rodat d12307c199 Replace the block_found global with explicit data-flow
As Pedro suggested on gdb-patches@ (see
https://sourceware.org/ml/gdb-patches/2015-05/msg00714.html), this
change makes symbol lookup functions return a structure that includes
both the symbol found and the block in which it was found.  This makes
it possible to get rid of the block_found global variable and thus makes
block hunting explicit.

gdb/

	* ada-exp.y (write_object_renaming): Replace struct
	ada_symbol_info with struct block_symbol.  Update field
	references accordingly.
	(block_lookup, select_possible_type_sym): Likewise.
	(find_primitive_type): Likewise.  Also update call to
	ada_lookup_symbol to extract the symbol itself.
	(write_var_or_type, write_name_assoc): Likewise.
	* ada-lang.h (struct ada_symbol_info): Remove.
	(ada_lookup_symbol_list): Replace struct ada_symbol_info with
	struct block_symbol.
	(ada_lookup_encoded_symbol, user_select_syms): Likewise.
	(ada_lookup_symbol): Return struct block_symbol instead of a
	mere symbol.
	* ada-lang.c (defns_collected): Replace struct ada_symbol_info
	with struct block_symbol.
	(resolve_subexp, ada_resolve_function, sort_choices,
	user_select_syms, is_nonfunction, add_defn_to_vec,
	num_defns_collected, defns_collected,
	symbols_are_identical_enums, remove_extra_symbols,
	remove_irrelevant_renamings, add_lookup_symbol_list_worker,
	ada_lookup_symbol_list, ada_iterate_over_symbols,
	ada_lookup_encoded_symbol, get_var_value): Likewise.
	(ada_lookup_symbol): Return a block_symbol instead of a mere
	symbol.  Replace struct ada_symbol_info with struct
	block_symbol.
	(ada_lookup_symbol_nonlocal): Likewise.
	(standard_lookup): Make block passing explicit through
	lookup_symbol_in_language.
	* ada-tasks.c (get_tcb_types_info): Update the calls to
	lookup_symbol_in_language to extract the mere symbol out of the
	returned value.
	(ada_tasks_inferior_data_sniffer): Likewise.
	* ax-gdb.c (gen_static_field): Likewise for the call to
	lookup_symbol.
	(gen_maybe_namespace_elt): Deal with struct symbol_in_block from
	lookup functions.
	(gen_expr): Likewise.
	* c-exp.y: Likewise.  Remove uses of block_found.
	(lex_one_token, classify_inner_name, c_print_token): Likewise.
	(classify_name): Likewise.  Rename the "sym" local variable to
	"bsym".
	* c-valprint.c (print_unpacked_pointer): Likewise.
	* compile/compile-c-symbols.c (convert_symbol_sym): Promote the
	"sym" parameter from struct symbol * to struct block_symbol.
	Use it to remove uses of block_found.  Deal with struct
	symbol_in_block from lookup functions.
	(gcc_convert_symbol): Likewise.  Update the call to
	convert_symbol_sym.
	* compile/compile-object-load.c (compile_object_load): Deal with
	struct symbol_in_block from lookup functions.
	* cp-namespace.c (cp_lookup_nested_symbol_1,
	cp_lookup_nested_symbol, cp_lookup_bare_symbol,
	cp_search_static_and_baseclasses,
	cp_lookup_symbol_in_namespace, cp_lookup_symbol_via_imports,
	cp_lookup_symbol_imports_or_template,
	cp_lookup_symbol_via_all_imports, cp_lookup_symbol_namespace,
	lookup_namespace_scope, cp_lookup_nonlocal,
	find_symbol_in_baseclass): Return struct symbol_in_block instead
	of mere symbols and deal with struct symbol_in_block from lookup
	functions.
	* cp-support.c (inspect_type, replace_typedefs,
	cp_lookup_rtti_type): Deal with struct symbol_in_block from
	lookup functions.
	* cp-support.h (cp_lookup_symbol_nonlocal,
	cp_lookup_symbol_from_namespace,
	cp_lookup_symbol_imports_or_template, cp_lookup_nested_symbol):
	Return struct symbol_in_block instead of mere symbols.
	* d-exp.y (d_type_from_name, d_module_from_name, push_variable,
	push_module_name):
	Deal with struct symbol_in_block from lookup functions.  Remove
	uses of block_found.
	* eval.c (evaluate_subexp_standard): Update call to
	cp_lookup_symbol_namespace.
	* f-exp.y: Deal with struct symbol_in_block from lookup
	functions.  Remove uses of block_found.
	(yylex): Likewise.
	* gdbtypes.c (lookup_typename, lookup_struct, lookup_union,
	lookup_enum, lookup_template_type, check_typedef): Deal with
	struct symbol_in_block from lookup functions.
	* guile/scm-frame.c (gdbscm_frame_read_var): Likewise.
	* guile/scm-symbol.c (gdbscm_lookup_symbol): Likewise.
	(gdbscm_lookup_global_symbol): Likewise.
	* gnu-v3-abi.c (gnuv3_get_typeid_type): Likewise.
	* go-exp.y: Likewise.  Remove uses of block_found.
	(package_name_p, classify_packaged_name, classify_name):
	Likewise.
	* infrun.c (insert_exception_resume_breakpoint): Likewise.
	* jv-exp.y (push_variable): Likewise.
	* jv-lang.c (java_lookup_class, get_java_object_type): Likewise.
	* language.c (language_bool_type): Likewise.
	* language.h (struct language_defn): Update
	la_lookup_symbol_nonlocal to return a struct symbol_in_block
	rather than a mere symbol.
	* linespec.c (find_label_symbols): Deal with struct
	symbol_in_block from lookup functions.
	* m2-exp.y: Likewise.  Remove uses of block_found.
	(yylex): Likewise.
	* mi/mi-cmd-stack.c (list_args_or_locals): Likewise.
	* objc-lang.c (lookup_struct_typedef, find_imps): Likewise.
	* p-exp.y: Likewise.  Remove uses of block_found.
	(yylex): Likewise.
	* p-valprint.c (pascal_val_print): Likewise.
	* parse.c (write_dollar_variable): Likewise.  Remove uses of
	block_found.
	* parser-defs.h (struct symtoken): Turn the SYM field into a
	struct symbol_in_block.
	* printcmd.c (address_info): Deal with struct symbol_in_block
	from lookup functions.
	* python/py-frame.c (frapy_read_var): Likewise.
	* python/py-symbol.c (gdbpy_lookup_symbol,
	gdbpy_lookup_global_symbol): Likewise.
	* skip.c (skip_function_command): Likewise.
	* solib-darwin.c (darwin_lookup_lib_symbol): Return a struct
	symbol_in_block instead of a mere symbol.
	* solib-spu.c (spu_lookup_lib_symbol): Likewise.
	* solib-svr4.c (elf_lookup_lib_symbol): Likewise.
	* solib.c (solib_global_lookup): Likewise.
	* solist.h (solib_global_lookup): Likewise.
	(struct target_so_ops): Update lookup_lib_global_symbol to
	return a struct symbol_in_block rather than a mere symbol.
	* source.c (select_source_symtab): Deal with struct
	symbol_in_block from lookup functions.
	* stack.c (print_frame_args, iterate_over_block_arg_vars):
	Likewise.
	* symfile.c (set_initial_language): Likewise.
	* symtab.c (SYMBOL_LOOKUP_FAILED): Turn into a struct
	symbol_in_block.
	(SYMBOL_LOOKUP_FAILED_P): New predicate as a macro.
	(struct symbol_cache_slot): Turn the FOUND field into a struct
	symbol_in_block.
	(block_found): Remove.
	(eq_symbol_entry): Update to deal with struct symbol_in_block in
	cache slots.
	(symbol_cache_lookup): Return a struct symbol_in_block rather
	than a mere symbol.
	(symbol_cache_mark_found): Add a BLOCK parameter to fill
	appropriately the cache slots.  Update callers.
	(symbol_cache_dump): Update cache slots handling to the type
	change.
	(lookup_symbol_in_language, lookup_symbol, lookup_language_this,
	lookup_symbol_aux, lookup_local_symbol,
	lookup_symbol_in_objfile, lookup_global_symbol_from_objfile,
	lookup_symbol_in_objfile_symtabs,
	lookup_symbol_in_objfile_from_linkage_name,
	lookup_symbol_via_quick_fns, basic_lookup_symbol_nonlocal,
	lookup_symbol_in_static_block, lookup_static_symbol,
	lookup_global_symbol):
	Return a struct symbol_in_block rather than a mere symbol.  Deal
	with struct symbol_in_block from other lookup functions.  Remove
	uses of block_found.
	(lookup_symbol_in_block): Remove uses of block_found.
	(struct global_sym_lookup_data): Turn the RESULT field into a
	struct symbol_in_block.
	(lookup_symbol_global_iterator_cb): Update references to the
	RESULT field.
	(search_symbols): Deal with struct symbol_in_block from lookup
	functions.
	* symtab.h (struct symbol_in_block): New structure.
	(block_found): Remove.
	(lookup_symbol_in_language, lookup_symbol,
	basic_lookup_symbol_nonlocal, lookup_symbol_in_static_block,
	looku_static_symbol, lookup_global_symbol,
	lookup_symbol_in_block, lookup_language_this,
	lookup_global_symbol_from_objfile): Return a struct
	symbol_in_block rather than just a mere symbol.  Update comments
	to remove mentions of block_found.
	* valops.c (find_function_in_inferior,
	value_struct_elt_for_reference, value_maybe_namespace_elt,
	value_of_this):  Deal with struct symbol_in_block from lookup
	functions.
	* value.c (value_static_field, value_fn_field): Likewise.
2015-08-01 10:55:44 +02:00
..
lib Add Guile frame-read-register command 2015-04-09 14:39:00 +02:00
guile-internal.h C++ keyword cleanliness, mostly auto-generated 2015-02-27 16:33:07 +00:00
guile.c [guile] Run finalizers from GDB thread 2015-03-11 13:07:53 +01:00
guile.h Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
README
scm-arch.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-auto-load.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-block.c Split TRY_CATCH into TRY + CATCH 2015-03-07 15:14:14 +00:00
scm-breakpoint.c Mostly trivial enum fixes 2015-07-31 13:19:53 -04:00
scm-cmd.c Mostly trivial enum fixes 2015-07-31 13:19:53 -04:00
scm-disasm.c Split TRY_CATCH into TRY + CATCH 2015-03-07 15:14:14 +00:00
scm-exception.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-frame.c Replace the block_found global with explicit data-flow 2015-08-01 10:55:44 +02:00
scm-gsmob.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-iterator.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-lazy-string.c Split TRY_CATCH into TRY + CATCH 2015-03-07 15:14:14 +00:00
scm-math.c Remove CHECK_TYPEDEF, use check_typedef instead 2015-07-14 16:42:16 -04:00
scm-objfile.c Add objfile-progspace to Guile interface 2015-03-11 14:20:06 +01:00
scm-param.c Mostly trivial enum fixes 2015-07-31 13:19:53 -04:00
scm-ports.c Add support for unbuffered and zero sized Guile ports. 2015-05-16 12:14:26 -07:00
scm-pretty-print.c Mostly trivial enum fixes 2015-07-31 13:19:53 -04:00
scm-progspace.c Update year range in copyright notice of all files owned by the GDB project. 2015-01-01 13:32:14 +04:00
scm-safe-call.c [guile] Run finalizers from GDB thread 2015-03-11 13:07:53 +01:00
scm-string.c Mostly trivial enum fixes 2015-07-31 13:19:53 -04:00
scm-symbol.c Replace the block_found global with explicit data-flow 2015-08-01 10:55:44 +02:00
scm-symtab.c Split TRY_CATCH into TRY + CATCH 2015-03-07 15:14:14 +00:00
scm-type.c Split TRY_CATCH into TRY + CATCH 2015-03-07 15:14:14 +00:00
scm-utils.c Remove redundant include directives. 2015-06-24 13:52:29 +01:00
scm-value.c Remove CHECK_TYPEDEF, use check_typedef instead 2015-07-14 16:42:16 -04:00

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README for gdb/guile
====================

This file contains important notes for gdb/guile developers.
["gdb/guile" refers to the directory you found this file in]

Nomenclature:

  In the implementation we use "Scheme" or "Guile" depending on context.
  And sometimes it doesn't matter.
  Guile is Scheme, and for the most part this is what we present to the user
  as well.  However, to highlight the fact that it is Guile, the GDB commands
  that invoke Scheme functions are named "guile" and "guile-repl",
  abbreviated "gu" and "gr" respectively.

Co-existence with Python:

  Keep the user interfaces reasonably consistent, but don't shy away from
  providing a clearer (or more Scheme-friendly/consistent) user interface
  where appropriate.

  Additions to Python support or Scheme support don't require corresponding
  changes in the other scripting language.

  Scheme-wrapped breakpoints are created lazily so that if the user
  doesn't use Scheme s/he doesn't pay any cost.

Importing the gdb module into Scheme:

  To import the gdb module:
  (gdb) guile (use-modules (gdb))

  If you want to add a prefix to gdb module symbols:
  (gdb) guile (use-modules ((gdb) #:renamer (symbol-prefix-proc 'gdb:)))
  This gives every symbol a "gdb:" prefix which is a common convention.
  OTOH it's more to type.

Implementation/Hacking notes:

  Don't use scm_is_false.
  For this C function, () == #f (a la Lisp) and it's not clear how treating
  them as equivalent for truth values will affect the GDB interface.
  Until the effect is clear avoid them.
  Instead use gdbscm_is_false, gdbscm_is_true, gdbscm_is_bool.
  There are macros in guile-internal.h to enforce this.

  Use gdbscm_foo as the name of functions that implement Scheme procedures
  to provide consistent naming in error messages.  The user can see "gdbscm"
  in the name and immediately know where the function came from.

  All smobs contain gdb_smob or chained_gdb_smob as the first member.
  This provides a mechanism for extending them in the Scheme side without
  tying GDB to the details.

  The lifetime of a smob, AIUI, is decided by the containing SCM.
  When there is no longer a reference to the containing SCM then the
  smob can be GC'd.  Objects that have references from outside of Scheme,
  e.g., breakpoints, need to be protected from GC.

  Don't do something that can cause a Scheme exception inside a TRY_CATCH,
  and, in code that can be called from Scheme, don't do something that can
  cause a GDB exception outside a TRY_CATCH.
  This makes the code a little tricky to write sometimes, but it is a
  rule imposed by the programming environment.  Bugs often happen because
  this rule is broken.  Learn it, follow it.

Coding style notes:

  - If you find violations to these rules, let's fix the code.
    Some attempt has been made to be consistent, but it's early.
    Over time we want things to be more consistent, not less.

  - None of this really needs to be read.  Instead, do not be creative:
    Monkey-See-Monkey-Do hacking should generally Just Work.

  - Absence of the word "typically" means the rule is reasonably strict.

  - The gdbscm_initialize_foo function (e.g., gdbscm_initialize_values)
    is the last thing to appear in the file, immediately preceded by any
    tables of exported variables and functions.

  - In addition to these of course, follow GDB coding conventions.

General naming rules:

  - The word "object" absent any modifier (like "GOOPS object") means a
    Scheme object (of any type), and is never used otherwise.
    If you want to refer to, e.g., a GOOPS object, say "GOOPS object".

  - Do not begin any function, global variable, etc. name with scm_.
    That's what the Guile implementation uses.
    (kinda obvious, just being complete).

  - The word "invalid" carries a specific connotation.  Try not to use it
    in a different way.  It means the underlying GDB object has disappeared.
    For example, a <gdb:objfile> smob becomes "invalid" when the underlying
    objfile is removed from GDB.

  - We typically use the word "exception" to mean Scheme exceptions,
    and we typically use the word "error" to mean GDB errors.

Comments:

  - function comments for functions implementing Scheme procedures begin with
    a description of the Scheme usage.  Example:
    /* (gsmob-aux gsmob) -> object */

  - the following comment appears after the copyright header:
    /* See README file in this directory for implementation notes, coding
       conventions, et.al.  */

Smob naming:

  - gdb smobs are named, internally, "gdb:foo"
  - in Guile they become <gdb:foo>, that is the convention for naming classes
    and smobs have rudimentary GOOPS support (they can't be inherited from,
    but generics can work with them)
  - in comments use the Guile naming for smobs,
    i.e., <gdb:foo> instead of gdb:foo.
    Note: This only applies to smobs.  Exceptions are also named gdb:foo,
    but since they are not "classes" they are not wrapped in <>.
  - smob names are stored in a global, and for simplicity we pass this
    global as the "expected type" parameter to SCM_ASSERT_TYPE, thus in
    this instance smob types are printed without the <>.
    [Hmmm, this rule seems dated now.  Plus I18N rules in GDB are not always
    clear, sometimes we pass the smob name through _(), however it's not
    clear that's actually a good idea.]

Type naming:

  - smob structs are typedefs named foo_smob

Variable naming:

  - "scm" by itself is reserved for arbitrary Scheme objects

  - variables that are pointers to smob structs are named <char>_smob or
    <char><char>_smob, e.g., f_smob for a pointer to a frame smob

  - variables that are gdb smob objects are typically named <char>_scm or
    <char><char>_scm, e.g., f_scm for a <gdb:frame> object

  - the name of the first argument for method-like functions is "self"

Function naming:

  General:

  - all non-static functions have a prefix,
    either gdbscm_ or <char><char>scm_ [or <char><char><char>scm_]

  - all functions that implement Scheme procedures have a gdbscm_ prefix,
    this is for consistency and readability of Scheme exception text

  - static functions typically have a prefix
    - the prefix is typically <char><char>scm_ where the first two letters
      are unique to the file or class the function works with.
      E.g., the scm-arch.c prefix is arscm_.
      This follows something used in gdb/python in some places,
      we make it formal.

  - if the function is of a general nature, or no other prefix works,
    use gdbscm_

  Conversion functions:

  - the from/to in function names follows from libguile's existing style
  - conversions from/to Scheme objects are named:
      prefix_scm_from_foo: converts from foo to scm
      prefix_scm_to_foo: converts from scm to foo

  Exception handling:

  - functions that may throw a Scheme exception have an _unsafe suffix
    - This does not apply to functions that implement Scheme procedures.
    - This does not apply to functions whose explicit job is to throw
      an exception.  Adding _unsafe to gdbscm_throw is kinda superfluous. :-)
  - functions that can throw a GDB error aren't adorned with _unsafe

  - "_safe" in a function name means it will never throw an exception
    - Generally unnecessary, since the convention is to mark the ones that
      *can* throw an exception.  But sometimes it's useful to highlight the
      fact that the function is safe to call without worrying about exception
      handling.

  - except for functions that implement Scheme procedures, all functions
    that can throw exceptions (GDB or Scheme) say so in their function comment

  - functions that don't throw an exception, but still need to indicate to
    the caller that one happened (i.e., "safe" functions), either return
    a <gdb:exception> smob as a result or pass it back via a parameter.
    For this reason don't pass back <gdb:exception> smobs for any other
    reason.  There are functions that explicitly construct <gdb:exception>
    smobs.  They're obviously the, umm, exception.

  Internal functions:

  - internal Scheme functions begin with "%" and are intentionally undocumented
    in the manual

  Standard Guile/Scheme conventions:

  - predicates that return Scheme values have the suffix _p and have suffix "?"
    in the Scheme procedure's name
  - functions that implement Scheme procedures that modify state have the
    suffix _x and have suffix "!" in the Scheme procedure's name
  - object predicates that return a C truth value are named prefix_is_foo
  - functions that set something have "set" at the front (except for a prefix)
    write this: gdbscm_set_gsmob_aux_x implements (set-gsmob-aux! ...)
    not this: gdbscm_gsmob_set_aux_x implements (gsmob-set-aux! ...)

Doc strings:

  - there are lots of existing examples, they should be pretty consistent,
    use them as boilerplate/examples
  - begin with a one line summary (can be multiple lines if necessary)
  - if the arguments need description:
    - blank line
    - "  Arguments: arg1 arg2"
      "    arg1: blah ..."
      "    arg2: blah ..."
  - if the result requires more description:
    - blank line
    - "  Returns:"
      "    Blah ..."
  - if it's important to list exceptions that can be thrown:
    - blank line
    - "  Throws:"
      "    exception-name: blah ..."