gdb's language support is mainly driven by the symbol reader, although it is possible for the user to set the source language manually.
gdb chooses the source language by looking at the extension of the file recorded in the debug info; .c means C, .f means Fortran, etc. It may also use a special-purpose language identifier if the debug format supports it, like with DWARF.
To add other languages to gdb's expression parser, follow the following steps:
union exp_elementlist are in parse.c.
Since we can't depend upon everyone having Bison, and YACC produces parsers that define a bunch of global names, the following lines must be included at the top of the YACC parser, to prevent the various parsers from defining the same global names:
#define yyparse lang_parse #define yylex lang_lex #define yyerror lang_error #define yylval lang_lval #define yychar lang_char #define yydebug lang_debug #define yypact lang_pact #define yyr1 lang_r1 #define yyr2 lang_r2 #define yydef lang_def #define yychk lang_chk #define yypgo lang_pgo #define yyact lang_act #define yyexca lang_exca #define yyerrflag lang_errflag #define yynerrs lang_nerrs
At the bottom of your parser, define a
struct language_defn and
initialize it with the right values for your language. Define an
initialize_lang routine and have it call
‘add_language(lang_language_defn)’ to tell the rest of gdb
that your language exists. You'll need some other supporting variables
and functions, which will be used via pointers from your
_language_defn. See the declaration of
language_defn in language.h, and the other *-exp.y files,
for more information.
evaluate_subexpfunction defined in the file eval.c. Add cases for new opcodes in two functions from parse.c:
length_of_subexp. These compute the number of
exp_elements that a given operation takes up.
enum languagein defs.h.
Update the routines in language.c so your language is included. These routines include type predicates and such, which (in some cases) are language dependent. If your language does not appear in the switch statement, an error is reported.
Also included in language.c is the code that updates the variable
current_language, and the routines that translate the
language_lang enumerated identifier into a printable
Update the function
_initialize_language to include your
language. This function picks the default language upon startup, so is
dependent upon which languages that gdb is built for.
allocate_symtab in symfile.c and/or symbol-reading
code so that the language of each symtab (source file) is set properly.
This is used to determine the language to use at each stack frame level.
Currently, the language is set based upon the extension of the source
file. If the language can be better inferred from the symbol
information, please set the language of the symtab in the symbol-reading
Add helper code to
print_subexp (in expprint.c) to handle any new
expression opcodes you have added to expression.h. Also, add the
printed representations of your operators to
parse_exp_1(defined in parse.c).
OBJS, otherwise your code may not get linked in, or, worse yet, it may not get
tarred into the distribution!