Handle custom completion match prefix / LCD

A following patch will add support for wild matching for C++ symbols,
making completing on "b push_ba" on a C++ program complete to
std::vector<...>::push_back, std::string::push_back etc., like:

 (gdb) b push_ba[TAB]
 std::vector<...>::push_back(....)
 std::string<...>::push_back(....)

Currently, we compute the "lowest common denominator" between all
completion candidates (what the input line is adjusted to) as the
common prefix of all matches.  That's problematic with wild matching
as above, as then we'd end up with TAB changing the input line to
"b std::", losing the original input, like:

 (gdb) b push_ba[TAB]
 std::vector<...>::push_back(....)
 std::string<...>::push_back(....)
 (gdb) b std::

while obviously we'd want it to adjust itself to "b push_back(" instead:

 (gdb) b push_ba[TAB]
 std::vector<...>::push_back(....)
 std::string<...>::push_back(....)
 (gdb) b push_back(

This patch adds the core code necessary to support this, though
nothing really makes use of it yet in this patch.

gdb/ChangeLog:
2017-11-29  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_lookup_name_info::matches): Change type of
	parameter from completion_match to completion_match_result.
	Adjust.
	(do_wild_match, do_full_match, ada_symbol_name_matches): Likewise.
	* completer.c (completion_tracker::maybe_add_completion): Add
	match_for_lcd parameter and use it.
	(completion_tracker::add_completion): Likewise.
	* completer.h (class completion_match_for_lcd): New class.
	(completion_match_result::match_for_lcd): New field.
	(completion_match_result::set_match): New method.
	(completion_tracker): Add comments.
	(completion_tracker::add_completion): Add match_for_lcd parameter.
	(completion_tracker::reset_completion_match_result): Reset
	match_for_lcd too.
	(completion_tracker::maybe_add_completion): Add match_for_lcd
	parameter.
	(completion_tracker::m_lowest_common_denominator_unique): Extend
	comments.
	* cp-support.c (cp_symbol_name_matches_1)
	(cp_fq_symbol_name_matches): Change type of parameter from
	completion_match to completion_match_result.  Adjust.
	* language.c (default_symbol_name_matcher): Change type of
	parameter from completion_match to completion_match_result.
	Adjust.
	* language.h (completion_match_for_lcd): Forward declare.
	(default_symbol_name_matcher): Change type of parameter from
	completion_match to completion_match_result.
	* symtab.c (compare_symbol_name): Adjust.
	(completion_list_add_name): Pass the match_for_lcd to the tracker.
	* symtab.h (ada_lookup_name_info::matches): Change type of
	parameter from completion_match to completion_match_result.
	(symbol_name_matcher_ftype): Likewise, and update comments.

1 files changed, 2 insertions, 1 deletions

diff --git a/gdb/language.h b/gdb/language.h
index 34f5692..47ad8da 100644
--- a/gdb/language.h
+++ b/gdb/language.h
@@ -37,6 +37,7 @@ struct type_print_options;
 struct lang_varobj_ops;
 struct parser_state;
 struct compile_instance;
+struct completion_match_for_lcd;
 
 #define MAX_FORTRAN_DIMS  7	/* Maximum number of F77 array dims.  */
 
@@ -629,7 +630,7 @@ void c_get_string (struct value *value, gdb_byte **buffer, int *length,
 extern bool default_symbol_name_matcher
   (const char *symbol_search_name,
    const lookup_name_info &lookup_name,
-   completion_match *match);
+   completion_match_result *comp_match_res);
 
 /* Get LANG's symbol_name_matcher method for LOOKUP_NAME.  Returns
    default_symbol_name_matcher if not set.  */