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+From: Paul Hilfinger <hilfingr at gnat dot com>
+To: gdb-patches at sources dot redhat dot com
+Cc: drow at false dot org, jimb at redhat dot com, eliz at gnu dot org
+In-reply-to: <20040609131240 dot GA7587 at nevyn dot them dot org> (message from Daniel
+ Jacobowitz on Wed, 9 Jun 2004 09:12:40 -0400)
+Subject: Re: [RFA]: Turn on Ada support, take 2
+References: <20040608090758.C59CAF2940@nile.gnat.com> <vt2aczd8aah.fsf@zenia.home> <20040609131240.GA7587@nevyn.them.org>
+Message-Id: <20040616084237.F02D1F292A@nile.gnat.com>
+Date: Wed, 16 Jun 2004 04:42:37 -0400 (EDT)
+X-Virus-Scanned: by amavisd-new at nile.gnat.com
+
+
+
+Here is an update to the patch I sent previously. In this version, I have
+
+1. Removed the compilation of ada-tasks.o, since we have not yet turned
+ on any of it in the public version.
+
+2. Responded to most of Eli's comments. I will have to consider the
+ issue of formating things like 'Address, since the standard rendering
+ in info files provided by the technically appropriate marker,
+ @code, looks rather bad (in my opinion), due to the adjacent quotes
+ at the beginning.
+
+A previous patch to the Ada sources added some conditionalization to mark code
+that is not yet used in the public version (for the benefit of reviewers).
+
+
+ChangeLogs:
+
+ 2004-06-16 Paul N. Hilfinger <Hilfinger@gnat.com>
+
+ Turn on initial Ada support (mainly expression evaluation).
+
+ * Makefile.in (ada_lex_c): Define
+ (HFILES_NO_SRCDIR): Add ada-lang.h.
+ (COMMON_OBS): Add ada-lang.o, ada-typeprint.o, ada-valprint.o.
+ (YYOBJ): Add ada-exp.o.
+ (rule .l.c): Generalize to not mention ada.
+ (ada-lex.o): Remove (ada-lex.c is included by ada-exp.y).
+ (ada-lang.o): Add dependencies on completer.h, gdb_obstack.h,
+ hashtab.h.
+ (ada-tasks.o): Add dependency on gdb_string.h.
+ (ada-valprint.o): Add dependency on gdb_string.h.
+
+ * symtab.c: Add dependency on ada-lang.h.
+ (symbol_natural_name): Add Ada case.
+ (symbol_demangled_name): Add Ada case.
+ (symbol_search_name): Add Ada case.
+
+ * symfile.c (init_filename_language_table): Add extensions for
+ Ada.
+
+ * defs.h (enum language): Add language_ada.
+
+ * gdbtypes.h (TYPE_FLAG_FIXED_INSTANCE): Define.
+
+2004-06-09 Paul N. Hilfinger <hilfinger@gnat.com>
+
+ * doc/gdb.texinfo (Filenames): Add Ada suffixes.
+ (Ada) New section.
+
+
+
+Index: gdb/Makefile.in
+===================================================================
+RCS file: /cvs/src/src/gdb/Makefile.in,v
+retrieving revision 1.587
+diff -u -p -r1.587 Makefile.in
+--- gdb/Makefile.in 14 Jun 2004 20:40:39 -0000 1.587
++++ gdb/Makefile.in 16 Jun 2004 08:23:45 -0000
+@@ -616,6 +616,7 @@ nm_h = @nm_h@
+ # gdb/ headers
+ #
+
++ada_lex_c = ada-lex.c
+ ada_lang_h = ada-lang.h $(value_h) $(gdbtypes_h)
+ alphabsd_tdep_h = alphabsd-tdep.h
+ alpha_tdep_h = alpha-tdep.h
+@@ -833,7 +834,7 @@ HFILES_NO_SRCDIR = bcache.h buildsym.h c
+ symfile.h symfile-mem.h stabsread.h target.h terminal.h typeprint.h \
+ xcoffsolib.h \
+ macrotab.h macroexp.h macroscope.h \
+- c-lang.h f-lang.h \
++ ada-lang.h c-lang.h f-lang.h \
+ jv-lang.h \
+ m2-lang.h p-lang.h \
+ complaints.h valprint.h \
+@@ -894,7 +895,7 @@ COMMON_OBS = $(DEPFILES) $(YYOBJ) \
+ dbxread.o coffread.o coff-pe-read.o elfread.o \
+ dwarfread.o dwarf2read.o mipsread.o stabsread.o corefile.o \
+ dwarf2expr.o dwarf2loc.o dwarf2-frame.o \
+- c-lang.o f-lang.o objc-lang.o \
++ ada-lang.o c-lang.o f-lang.o objc-lang.o \
+ ui-out.o cli-out.o \
+ varobj.o wrapper.o \
+ jv-lang.o jv-valprint.o jv-typeprint.o \
+@@ -902,8 +903,8 @@ COMMON_OBS = $(DEPFILES) $(YYOBJ) \
+ scm-exp.o scm-lang.o scm-valprint.o \
+ sentinel-frame.o \
+ complaints.o typeprint.o \
+- c-typeprint.o f-typeprint.o m2-typeprint.o \
+- c-valprint.o cp-valprint.o f-valprint.o m2-valprint.o \
++ ada-typeprint.o c-typeprint.o f-typeprint.o m2-typeprint.o \
++ ada-valprint.o c-valprint.o cp-valprint.o f-valprint.o m2-valprint.o \
+ nlmread.o serial.o mdebugread.o top.o utils.o \
+ ui-file.o \
+ user-regs.o \
+@@ -927,6 +928,7 @@ YYFILES = c-exp.c \
+ f-exp.c m2-exp.c p-exp.c
+ YYOBJ = c-exp.o \
+ objc-exp.o \
++ ada-exp.o \
+ jv-exp.o \
+ f-exp.o m2-exp.o p-exp.o
+
+@@ -1495,7 +1497,7 @@ valprint.o: $(srcdir)/valprint.c
+ echo $(FLEX) -Isit $< ">" $@; \
+ $(FLEX) -Isit $< > $@; \
+ elif [ ! -f $@ -a ! -f $< ]; then \
+- echo "ada-lex.c missing and flex not available."; \
++ echo "$< missing and flex not available."; \
+ false; \
+ elif [ ! -f $@ ]; then \
+ echo "Warning: $*.c older than $*.l and flex not available."; \
+@@ -1522,18 +1524,18 @@ ada-lang.o: ada-lang.c $(gdb_string_h) $
+ $(gdbtypes_h) $(gdbcmd_h) $(expression_h) $(parser_defs_h) \
+ $(language_h) $(c_lang_h) $(inferior_h) $(symfile_h) $(objfiles_h) \
+ $(breakpoint_h) $(gdbcore_h) $(ada_lang_h) $(ui_out_h) $(block_h) \
+- $(infcall_h) $(dictionary_h)
+-ada-lex.o: ada-lex.c
++ $(completer_h) $(infcall_h) $(gdb_obstack_h) $(dictionary_h) \
++ $(hashtab_h)
+ ada-tasks.o: ada-tasks.c $(defs_h) $(command_h) $(value_h) $(language_h) \
+ $(inferior_h) $(symtab_h) $(target_h) $(regcache_h) $(gdbcore_h) \
+- $(gregset_h) $(ada_lang_h)
++ $(gregset_h) $(gdb_string_h) $(ada_lang_h)
+ ada-typeprint.o: ada-typeprint.c $(defs_h) $(gdb_obstack_h) $(bfd_h) \
+ $(symtab_h) $(gdbtypes_h) $(expression_h) $(value_h) $(gdbcore_h) \
+ $(target_h) $(command_h) $(gdbcmd_h) $(language_h) $(demangle_h) \
+ $(c_lang_h) $(typeprint_h) $(ada_lang_h) $(gdb_string_h)
+ ada-valprint.o: ada-valprint.c $(defs_h) $(symtab_h) $(gdbtypes_h) \
+ $(expression_h) $(value_h) $(demangle_h) $(valprint_h) $(language_h) \
+- $(annotate_h) $(ada_lang_h) $(c_lang_h) $(infcall_h)
++ $(annotate_h) $(ada_lang_h) $(c_lang_h) $(gdb_string_h) $(infcall_h)
+ aix-thread.o: aix-thread.c $(defs_h) $(gdb_assert_h) $(gdbthread_h) \
+ $(target_h) $(inferior_h) $(regcache_h) $(gdbcmd_h) $(language_h) \
+ $(ppc_tdep_h) $(gdb_string_h)
+Index: gdb/defs.h
+===================================================================
+RCS file: /cvs/src/src/gdb/defs.h,v
+retrieving revision 1.147
+diff -u -p -r1.147 defs.h
+--- gdb/defs.h 10 Jun 2004 20:05:43 -0000 1.147
++++ gdb/defs.h 16 Jun 2004 08:23:45 -0000
+@@ -220,6 +220,7 @@ enum language
+ language_asm, /* Assembly language */
+ language_scm, /* Scheme / Guile */
+ language_pascal, /* Pascal */
++ language_ada, /* Ada */
+ language_minimal /* All other languages, minimal support only */
+ };
+
+Index: gdb/gdbtypes.h
+===================================================================
+RCS file: /cvs/src/src/gdb/gdbtypes.h,v
+retrieving revision 1.53
+diff -u -p -r1.53 gdbtypes.h
+--- gdb/gdbtypes.h 2 Jun 2004 21:01:55 -0000 1.53
++++ gdb/gdbtypes.h 16 Jun 2004 08:23:45 -0000
+@@ -273,6 +273,17 @@ enum type_code
+ #define TYPE_ADDRESS_CLASS_ALL(t) (TYPE_INSTANCE_FLAGS(t) \
+ & TYPE_FLAG_ADDRESS_CLASS_ALL)
+
++/* The debugging formats (especially STABS) do not contain enough information
++ to represent all Ada types---especially those whose size depends on
++ dynamic quantities. Therefore, the GNAT Ada compiler includes
++ extra information in the form of additional type definitions
++ connected by naming conventions. This flag indicates that the
++ type is an ordinary (unencoded) GDB type that has been created from
++ the necessary run-time information, and does not need further
++ interpretation. Optionally marks ordinary, fixed-size GDB type. */
++
++#define TYPE_FLAG_FIXED_INSTANCE (1 << 15)
++
+ /* Array bound type. */
+ enum array_bound_type
+ {
+Index: gdb/symfile.c
+===================================================================
+RCS file: /cvs/src/src/gdb/symfile.c,v
+retrieving revision 1.132
+diff -u -p -r1.132 symfile.c
+--- gdb/symfile.c 15 Jun 2004 01:04:20 -0000 1.132
++++ gdb/symfile.c 16 Jun 2004 08:23:46 -0000
+@@ -2158,6 +2158,10 @@ init_filename_language_table (void)
+ add_filename_language (".pas", language_pascal);
+ add_filename_language (".p", language_pascal);
+ add_filename_language (".pp", language_pascal);
++ add_filename_language (".adb", language_ada);
++ add_filename_language (".ads", language_ada);
++ add_filename_language (".a", language_ada);
++ add_filename_language (".ada", language_ada);
+ }
+ }
+
+Index: gdb/symtab.c
+===================================================================
+RCS file: /cvs/src/src/gdb/symtab.c,v
+retrieving revision 1.132
+diff -u -p -r1.132 symtab.c
+--- gdb/symtab.c 10 Jun 2004 20:05:44 -0000 1.132
++++ gdb/symtab.c 16 Jun 2004 08:23:47 -0000
+@@ -41,6 +41,7 @@
+ #include "source.h"
+ #include "filenames.h" /* for FILENAME_CMP */
+ #include "objc-lang.h"
++#include "ada-lang.h"
+
+ #include "hashtab.h"
+
+@@ -632,17 +633,24 @@ symbol_init_demangled_name (struct gener
+ char *
+ symbol_natural_name (const struct general_symbol_info *gsymbol)
+ {
+- if ((gsymbol->language == language_cplus
+- || gsymbol->language == language_java
+- || gsymbol->language == language_objc)
+- && (gsymbol->language_specific.cplus_specific.demangled_name != NULL))
++ switch (gsymbol->language)
+ {
+- return gsymbol->language_specific.cplus_specific.demangled_name;
+- }
+- else
+- {
+- return gsymbol->name;
++ case language_cplus:
++ case language_java:
++ case language_objc:
++ if (gsymbol->language_specific.cplus_specific.demangled_name != NULL)
++ return gsymbol->language_specific.cplus_specific.demangled_name;
++ break;
++ case language_ada:
++ if (gsymbol->language_specific.cplus_specific.demangled_name != NULL)
++ return gsymbol->language_specific.cplus_specific.demangled_name;
++ else
++ return ada_decode_symbol (gsymbol);
++ break;
++ default:
++ break;
+ }
++ return gsymbol->name;
+ }
+
+ /* Return the demangled name for a symbol based on the language for
+@@ -650,13 +658,24 @@ symbol_natural_name (const struct genera
+ char *
+ symbol_demangled_name (struct general_symbol_info *gsymbol)
+ {
+- if (gsymbol->language == language_cplus
+- || gsymbol->language == language_java
+- || gsymbol->language == language_objc)
+- return gsymbol->language_specific.cplus_specific.demangled_name;
+-
+- else
+- return NULL;
++ switch (gsymbol->language)
++ {
++ case language_cplus:
++ case language_java:
++ case language_objc:
++ if (gsymbol->language_specific.cplus_specific.demangled_name != NULL)
++ return gsymbol->language_specific.cplus_specific.demangled_name;
++ break;
++ case language_ada:
++ if (gsymbol->language_specific.cplus_specific.demangled_name != NULL)
++ return gsymbol->language_specific.cplus_specific.demangled_name;
++ else
++ return ada_decode_symbol (gsymbol);
++ break;
++ default:
++ break;
++ }
++ return NULL;
+ }
+
+ /* Return the search name of a symbol---generally the demangled or
+#### gdb post-6.1 branch
+##@@ -664,7 +683,10 @@ symbol_demangled_name (struct general_sy
+## If there is no distinct demangled name, then returns the same value
+## (same pointer) as SYMBOL_LINKAGE_NAME. */
+## char *symbol_search_name (const struct general_symbol_info *gsymbol) {
+##- return symbol_natural_name (gsymbol);
+##+ if (gsymbol->language == language_ada)
+##+ return gsymbol->name;
+##+ else
+##+ return symbol_natural_name (gsymbol);
+## }
+##
+## /* Initialize the structure fields to zero values. */
+##
+Index: gdb/doc/gdb.texinfo
+===================================================================
+RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
+retrieving revision 1.206
+diff -u -p -r1.206 gdb.texinfo
+--- gdb/doc/gdb.texinfo 14 Jun 2004 22:26:33 -0000 1.206
++++ gdb/doc/gdb.texinfo 16 Jun 2004 08:23:53 -0000
+@@ -7741,6 +7741,11 @@ If a source file name ends in one of the
+ @value{GDBN} infers that its language is the one indicated.
+
+ @table @file
++@item .ada
++@itemx .ads
++@itemx .adb
++@itemx .a
++Ada source file.
+
+ @item .c
+ C source file
+@@ -8031,7 +8036,7 @@ being set automatically by @value{GDBN}.
+ @node Support
+ @section Supported languages
+
+-@value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
++@value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
+ @c This is false ...
+ Some @value{GDBN} features may be used in expressions regardless of the
+ language you use: the @value{GDBN} @code{@@} and @code{::} operators,
+@@ -8051,6 +8056,7 @@ language reference or tutorial.
+ * C:: C and C@t{++}
+ * Objective-C:: Objective-C
+ * Modula-2:: Modula-2
++* Ada:: Ada
+ @end menu
+
+ @node C
+@@ -8666,7 +8672,7 @@ the description of an object. However,
+ with certain Objective-C libraries that have a particular hook
+ function, @code{_NSPrintForDebugger}, defined.
+
+-@node Modula-2, , Objective-C, Support
++@node Modula-2, Ada, Objective-C, Support
+ @subsection Modula-2
+
+ @cindex Modula-2, @value{GDBN} support
+@@ -9109,6 +9115,481 @@ address can be specified by an integral
+ In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
+ interpreted as the beginning of a comment. Use @code{<>} instead.
+
++@node Ada
++@subsection Ada
++@cindex Ada
++
++The extensions made to @value{GDBN} for Ada only support
++output from the @sc{gnu} Ada (GNAT) compiler.
++Other Ada compilers are not currently supported, and
++attempting to debug executables produced by them is most likely
++to be difficult.
++
++
++@cindex expressions in Ada
++@menu
++* Ada Mode Intro:: General remarks on the Ada syntax
++ and semantics supported by Ada mode
++ in @value{GDBN}
++* Omissions from Ada:: Restrictions on the Ada expression syntax.
++* Additions to Ada:: Extensions of the Ada expression syntax.
++* Stopping Before Main Program:: Debugging the program during elaboration.
++* Ada Exceptions:: Setting breakpoints on exception handlers.
++* Ada Generic Units:: Dealing with generic instantiations.
++* Ada Glitches:: Known peculiarities of Ada mode.
++@end menu
++
++@node Ada Mode Intro
++@subsubsection Introduction
++@cindex Ada mode, general
++
++The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
++syntax, with some extensions.
++The philosophy behind the design of this subset is
++
++@itemize @bullet
++@item
++That @value{GDBN} should provide basic literals and access to operations for
++arithmetic, dereferencing, field selection, indexing, and subprogram calls,
++leaving more sophisticated computations to subprograms written into the
++program (which therefore may be called from @value{GDBN}).
++
++@item
++That type safety and strict adherence to Ada language restrictions
++are not particularly important to the @value{GDBN} user.
++
++@item
++That brevity is important to the @value{GDBN} user.
++@end itemize
++
++Thus, for brevity, the debugger acts as if there were
++implicit @code{with} and @code{use} clauses in effect for all user-written
++packages, making it unnecessary to fully qualify most names with
++their packages, regardless of context. Where this causes ambiguity,
++@value{GDBN} asks the user's intent.
++
++The debugger will start in Ada mode if it detects an Ada main program.
++As for other languages, it will enter Ada mode when stopped in a program that
++was translated from an Ada source file.
++
++While in Ada mode, you may use `@t{--}' for comments. This is useful
++mostly for documenting command files. The standard @value{GDBN} comment
++(@samp{#}) still works at the beginning of a line in Ada mode, but not in the
++middle (to allow based literals).
++
++The debugger supports limited overloading. Given a subprogram call in which
++the function symbol has multiple definitions, it will use the number of
++actual parameters and some information about their types to attempt to narrow
++the set of definitions. It also makes very limited use of context, preferring
++procedures to functions in the context of the @code{call} command, and
++functions to procedures elsewhere.
++
++@node Omissions from Ada
++@subsubsection Omissions from Ada
++@cindex Ada, omissions from
++
++Here are the notable omissions from the subset:
++
++@itemize @bullet
++@item
++Only a subset of the attributes are supported:
++
++@itemize @minus
++@item
++@t{'First}, @t{'Last}, and @t{'Length}
++ on array objects (not on types and subtypes).
++
++@item
++@t{'Min} and @t{'Max}.
++
++@item
++@t{'Pos} and @t{'Val}.
++
++@item
++@t{'Tag}.
++
++@item
++@t{'Range} on array objects (not subtypes), but only as the right
++operand of the membership (@code{in}) operator.
++
++@item
++@t{'Access}, @t{'Unchecked_Access}, and
++@t{'Unrestricted_Access} (a GNAT extension).
++
++@item
++@t{'Address}.
++@end itemize
++
++@item
++The names in
++@code{Characters.Latin_1} are not available and
++concatenation is not implemented. Thus, escape characters in strings are
++not currently available.
++
++@item
++Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
++equality of representations. They will generally work correctly
++for strings and arrays whose elements have integer or enumeration types.
++They may not work correctly for arrays whose element
++types have user-defined equality, for arrays of real values
++(in particular, IEEE-conformant floating point, because of negative
++zeroes and NaNs), and for arrays whose elements contain unused bits with
++indeterminate values.
++
++@item
++The other component-by-component array operations (@code{and}, @code{or},
++@code{xor}, @code{not}, and relational tests other than equality)
++are not implemented.
++
++@item
++There are no record or array aggregates.
++
++@item
++Dispatching subprogram calls are not implemented.
++
++@item
++The overloading algorithm is much more limited (i.e., less selective)
++than that of real Ada. It makes only limited use of the context in which a subexpression
++appears to resolve its meaning, and it is much looser in its rules for allowing
++type matches. As a result, some function calls will be ambiguous, and the user
++will be asked to choose the proper resolution.
++
++@item
++The @code{new} operator is not implemented.
++
++@item
++Entry calls are not implemented.
++
++@item
++Aside from printing, arithmetic operations on the native VAX floating-point
++formats are not supported.
++
++@item
++It is not possible to slice a packed array.
++@end itemize
++
++@node Additions to Ada
++@subsubsection Additions to Ada
++@cindex Ada, deviations from
++
++As it does for other languages, @value{GDBN} makes certain generic
++extensions to Ada (@pxref{Expressions}):
++
++@itemize @bullet
++@item
++If the expression @var{E} is a variable residing in memory
++(typically a local variable or array element) and @var{N} is
++a positive integer, then @code{@var{E}@@@var{N}} displays the values of
++@var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
++In Ada, this operator is generally not necessary, since its prime use
++is in displaying parts of an array, and slicing will usually do this in Ada.
++However, there are occasional uses when debugging programs
++in which certain debugging information has been optimized away.
++
++@item
++@code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
++in function or file @var{B}.'' When @var{B} is a file name, you must typically
++surround it in single quotes.
++
++@item
++The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
++@var{type} that appears at address @var{addr}.''
++
++@item
++A name starting with @samp{$} is a convenience variable
++(@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
++@end itemize
++
++In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
++to Ada:
++
++@itemize @bullet
++@item
++The assignment statement is allowed as an expression, returning
++its right-hand operand as its value. Thus, you may enter
++
++@smallexample
++set x := y + 3
++print A(tmp := y + 1)
++@end smallexample
++
++@item
++The semicolon is allowed as an ``operator,'' returning as its value
++the value of its right-hand operand.
++This allows, for example,
++complex conditional breaks:
++
++@smallexample
++break f
++condition 1 (report(i); k += 1; A(k) > 100)
++@end smallexample
++
++@item
++Rather than use catenation and symbolic character names to introduce special
++characters into strings, one may instead use a special bracket notation,
++which is also used to print strings. A sequence of characters of the form
++@samp{["@var{XX}"]} within a string or character literal denotes the
++(single) character whose numeric encoding is @var{XX} in hexadecimal. The
++sequence of characters @samp{["""]} also denotes a single quotation mark
++in strings. For example,
++@smallexample
++ "One line.["0a"]Next line.["0a"]"
++@end smallexample
++@noindent
++Contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
++period.
++
++@item
++The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
++@t{'Max} is optional (and is ignored in any case). For example, it is valid
++to write
++
++@smallexample
++print 'max(x, y)
++@end smallexample
++
++@item
++When printing arrays, @value{GDBN} uses positional notation when the
++array has a lower bound of 1, and uses a modified named notation otherwise.
++For example, a one-dimensional array of three integers with a lower bound of 3 might print as
++
++@smallexample
++(3 => 10, 17, 1)
++@end smallexample
++
++@noindent
++That is, in contrast to valid Ada, only the first component has a @code{=>}
++clause.
++
++@item
++You may abbreviate attributes in expressions with any unique,
++multi-character subsequence of
++their names (an exact match gets preference).
++For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
++in place of @t{a'length}.
++
++@item
++@cindex quoting Ada internal identifiers
++Since Ada is case-insensitive, the debugger normally maps identifiers you type
++to lower case. The GNAT compiler uses upper-case characters for
++some of its internal identifiers, which are normally of no interest to users.
++For the rare occasions when you actually have to look at them,
++enclose them in angle brackets to avoid the lower-case mapping.
++For example,
++@smallexample
++(gdb) print <JMPBUF_SAVE>[0]
++@end smallexample
++
++@item
++Printing an object of class-wide type or dereferencing an
++access-to-class-wide value will display all the components of the object's
++specific type (as indicated by its run-time tag). Likewise, component
++selection on such a value will operate on the specific type of the
++object.
++
++@end itemize
++
++@node Stopping Before Main Program
++@subsubsection Stopping at the Very Beginning
++
++@cindex breakpointing Ada elaboration code
++It is sometimes necessary to debug the program during elaboration, and
++before reaching the main procedure.
++As defined in the Ada Reference
++Manual, the elaboration code is invoked from a procedure called
++@code{adainit}. To run your program up to the beginning of
++elaboration, simply use the following two commands:
++@code{tbreak adainit} and @code{run}.
++
++@node Ada Exceptions
++@subsubsection Breaking on Ada Exceptions
++@cindex Ada, exceptions
++
++In Ada mode, you can set breakpoints that trip when your program raises
++selected exceptions.
++
++@table @code
++@kindex break exception
++@item break exception
++Set a breakpoint that trips whenever (any task in the) program raises
++any exception.
++
++@item break exception @var{name}
++Set a breakpoint that trips whenever (any task in the) program raises
++the exception @var{name}.
++
++When inserting a breakpoint on a specific exception for which an
++homonym entity exists in the application, it is necessary to prefix
++the exception name with its package name. In particular, if an entity
++sharing the same name as one of the standard exceptions has been defined,
++the exception name must be prefixed with package @code{Standard} when
++setting a breakpoint on this exception.
++
++@smallexample
++@iftex
++@leftskip=0.5cm
++@end iftex
++(gdb) break exception Standard.Constraint_Error
++@end smallexample
++
++@item break exception unhandled
++Set a breakpoint that trips whenever (any task in the) program raises an
++exception for which there is no handler.
++At the moment,
++depending on the implementation of exceptions used on your platform,
++this may not have quite the desired effect. Other forms of
++exception breaking stop the program at the point the exception is raised.
++In Ada implementations that use setjmp and longjmp to implement exception
++handling, however, unhandled exceptions are not detected until the
++affected task's stack is completely unwound. Thus, you find out that a
++task has terminated with an exception, but you aren't told where it was
++raised.
++
++@kindex info exceptions
++@item info exceptions
++@itemx info exceptions @var{regexp}
++The @code{info exceptions} command permits the user to examine all defined
++exceptions within Ada programs. With a regular expression, @var{regexp}, as
++argument, prints out only those exceptions whose name matches @var{regexp}.
++@end table
++
++@node Ada Generic Units
++@subsubsection Debugging Generic Units
++@cindex Ada, generic units
++
++GNAT always uses code expansion for generic instantiation. This means that
++each time an instantiation occurs, a complete copy of the original code is
++made with appropriate substitutions.
++
++It is not possible to refer to the original generic entities themselves
++in @value{GDBN} (there is no code to refer to), but it
++is certainly possible to debug a particular instance of a generic, simply by
++using the appropriate expanded names. For example, suppose that
++@code{Gen} is a generic package:
++
++@smallexample
++-- In file gen.ads:
++generic package Gen is
++ function F (v1 : Integer) return Integer;
++end Gen;
++
++-- In file gen.adb:
++package body Gen is
++ function F (v1 : Integer) return Integer is
++ begin
++ return v1+1; -- Line 5
++ end F;
++end Gen;
++@end smallexample
++
++@noindent
++and we have the following expansions
++
++@smallexample
++with Gen;
++procedure G is
++ package Gen1 is new Gen;
++ package Gen2 is new Gen;
++
++ I : Integer := 0;
++begin
++ I := Gen1.F (I);
++ I := Gen2.F (I);
++ I := Gen1.F (I);
++ I := Gen2.F (I);
++end;
++@end smallexample
++
++@noindent
++Then to break on a call to procedure @code{F} in the @code{Gen2} instance, simply
++use the command:
++
++@smallexample
++break G.Gen2.F
++@end smallexample
++
++When a breakpoint occurs, you can step through the code of the generic
++instance in the normal manner. You can also examine values of data in the
++normal manner, providing the appropriate generic package qualification to
++refer to non-local entities.
++
++@node Ada Glitches
++@subsubsection Known Peculiarities of Ada Mode
++@cindex Ada, problems
++
++Besides the omissions listed previously (@pxref{Omissions from Ada}),
++we know of several problems with and limitations of Ada mode in
++@value{GDBN},
++some of which will be fixed with planned future releases of the debugger
++and the GNU Ada compiler.
++
++@itemize @bullet
++@item
++Currently, the debugger
++has insufficient information to determine whether certain pointers represent
++pointers to objects or the objects themselves.
++Thus, the user may have to tack an extra @code{.all} after an expression
++to get it printed properly.
++
++@item
++Static constants that the compiler chooses not to materialize as objects in
++storage are invisible to the debugger.
++
++@item
++Named parameter associations in function argument lists are ignored (the
++argument lists are treated as positional).
++
++@item
++Many useful library packages are currently invisible to the debugger.
++
++@item
++Fixed-point arithmetic, conversions, input, and output is carried out using
++floating-point arithmetic, and may give results that only approximate those on
++the host machine.
++
++@item
++The type of the @t{'Address} attribute may not be @code{System.Address}.
++
++@item
++When stopped in a particular subprogram, you can access variables defined
++in other, lexically
++enclosing subprograms by their simple names. At the moment, however, this
++may not always work; it depends on whether the compiler happens to have
++made the necessary information (the ``static link'') available
++at execution time, which it can sometimes avoid. Of course,
++even in those cases where
++the compiler does not provide the information, you can still look at such
++variables by issuing the appropriate number of @code{up} commands to get to
++frame containing the variable you wish to see.
++Access to non-local variables does not, at the moment, work in
++the test expressions for conditional breakpoints
++(@pxref{Conditions, ,Break conditions}) unless you happen to specify these
++while stopped in the subprogram in which they are to be applied.
++
++@item
++Depending on the platform, it is not always possible to set breakpoints
++on nested functions by name (e.g., @code{break foo}). In effect, the
++nested functions act like local variables of the enclosing function.
++On these platforms, you must wait until @value{GDBN} is stopped in
++the enclosing function before using this form of @code{break} command.
++This is not much of a limitation, since you can still set a breakpoint on
++the first line of the desired function using the usual
++@code{break @var{file}:@var{line}} syntax.
++
++@item
++The GNAT compiler never generates the prefix @code{Standard} for any of
++the standard symbols defined by the Ada language. @value{GDBN} knows about
++this: it will strip the prefix from names when you use it, and will never
++look for a name you have so qualified among local symbols, nor match against
++symbols in other packages or subprograms. If you have
++defined entities anywhere in your program other than parameters and
++local variables whose simple names match names in @code{Standard},
++GNAT's lack of qualification here can cause confusion. When this happens,
++you can usually resolve the confusion
++by qualifying the problematic names with package
++@code{Standard} explicitly.
++@end itemize
++
+ @node Unsupported languages
+ @section Unsupported languages
+
+