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binutils-gdb/gdb/minsyms.h
Pedro Alves 74ea4be48e Introduce OP_VAR_MSYM_VALUE 
The previous patch left GDB with an inconsistency.  While with normal
expression evaluation the "unknown return type" error shows the name
of the function that misses debug info:

  (gdb) p getenv ("PATH")
  'getenv' has unknown return type; cast the call to its declared return type
   ^^^^^^

which can by handy in more complicated expressions, "ptype" does not:

  (gdb) ptype getenv ("PATH")
  function has unknown return type; cast the call to its declared return type
  ^^^^^^^^

This commit is a step toward fixing it.

The problem is that while evaluating the expression above, we have no
reference to the minimal symbol where we could extract the name from.
This is because the resulting expression tree has no reference to the
minsym at all.  During parsing, the type and address of the minsym are
extracted and an UNOP_MEMVAL / UNOP_MEMVAL_TLS operator is generated
(see write_exp_elt_msym).  With "set debug expression", here's what
you see:

            0  OP_FUNCALL            Number of args: 0
            3    UNOP_MEMVAL           Type @0x565334a51930 (<text variable, no debug info>)
            6      OP_LONG               Type @0x565334a51c60 (__CORE_ADDR), value 140737345035648 (0x7ffff7751d80)

The "print" case finds the function name, because
call_function_by_hand looks up the function by address again.
However, for "ptype", we don't reach that code, because obviously we
don't really call the function.

Unlike minsym references, references to variables with debug info have
a pointer to the variable's symbol in the expression tree, with
OP_VAR_VALUE:

  (gdb) ptype main()
  ...
            0  OP_FUNCALL            Number of args: 0
            3    OP_VAR_VALUE          Block @0x0, symbol @0x559bbbd9b358 (main(int, char**))
  ...

so I don't see why do minsyms need to be different.  So to prepare for
fixing the missing function name issue, this commit adds a new
OP_VAR_MSYM_VALUE operator that mimics OP_VAR_VALUE, except that it's
for minsyms instead of debug symbols.  For infcalls, we now get
expressions like these:

            0  OP_FUNCALL            Number of args: 0
            3    OP_VAR_MSYM_VALUE     Objfile @0x1e41bf0, msymbol @0x7fffe599b000 (getenv)

In the following patch, we'll make OP_FUNCALL extract the function
name from the symbol stored in OP_VAR_VALUE/OP_VAR_MSYM_VALUE.

OP_VAR_MSYM_VALUE will be used more in a later patch in the series
too.

gdb/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (resolve_subexp): Handle OP_VAR_MSYM_VALUE.
	* ax-gdb.c (gen_msym_var_ref): New function.
	(gen_expr): Handle OP_VAR_MSYM_VALUE.
	* eval.c (evaluate_var_msym_value): New function.
	* eval.c (evaluate_subexp_standard): Handle OP_VAR_MSYM_VALUE.
	<OP_FUNCALL>: Extract function name from symbol/minsym and pass it
	to call_function_by_hand.
	* expprint.c (print_subexp_standard, dump_subexp_body_standard):
	Handle OP_VAR_MSYM_VALUE.
	(union exp_element) <msymbol>: New field.
	* minsyms.h (struct type): Forward declare.
	(find_minsym_type_and_address): Declare.
	* parse.c (write_exp_elt_msym): New function.
	(write_exp_msymbol): Delete, refactored as ...
	(find_minsym_type_and_address): ... this new function.
	(write_exp_msymbol): Reimplement using OP_VAR_MSYM_VALUE.
	(operator_length_standard, operator_check_standard): Handle
	OP_VAR_MSYM_VALUE.
	* std-operator.def (OP_VAR_MSYM_VALUE): New.
2017-09-04 20:21:13 +01:00

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/* Minimal symbol table definitions for GDB.
Copyright (C) 2011-2017 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/>. */
#ifndef MINSYMS_H
#define MINSYMS_H
struct type;
/* Several lookup functions return both a minimal symbol and the
objfile in which it is found. This structure is used in these
cases. */
struct bound_minimal_symbol
{
/* The minimal symbol that was found, or NULL if no minimal symbol
was found. */
struct minimal_symbol *minsym;
/* If MINSYM is not NULL, then this is the objfile in which the
symbol is defined. */
struct objfile *objfile;
};
/* This header declares most of the API for dealing with minimal
symbols and minimal symbol tables. A few things are declared
elsewhere; see below.
A minimal symbol is a symbol for which there is no direct debug
information. For example, for an ELF binary, minimal symbols are
created from the ELF symbol table.
For the definition of the minimal symbol structure, see struct
minimal_symbol in symtab.h.
Minimal symbols are stored in tables attached to an objfile; see
objfiles.h for details. Code should generally treat these tables
as opaque and use functions provided by minsyms.c to inspect them.
*/
struct msym_bunch;
/* An RAII-based object that is used to record minimal symbols while
they are being read. */
class minimal_symbol_reader
{
public:
/* Prepare to start collecting minimal symbols. This should be
called by a symbol reader to initialize the minimal symbol
module. */
explicit minimal_symbol_reader (struct objfile *);
~minimal_symbol_reader ();
/* Install the minimal symbols that have been collected into the
given objfile. */
void install ();
/* Record a new minimal symbol. This is the "full" entry point;
simpler convenience entry points are also provided below.
This returns a new minimal symbol. It is ok to modify the returned
minimal symbol (though generally not necessary). It is not ok,
though, to stash the pointer anywhere; as minimal symbols may be
moved after creation. The memory for the returned minimal symbol
is still owned by the minsyms.c code, and should not be freed.
Arguments are:
NAME - the symbol's name
NAME_LEN - the length of the name
COPY_NAME - if true, the minsym code must make a copy of NAME. If
false, then NAME must be NUL-terminated, and must have a lifetime
that is at least as long as OBJFILE's lifetime.
ADDRESS - the address of the symbol
MS_TYPE - the type of the symbol
SECTION - the symbol's section
*/
struct minimal_symbol *record_full (const char *name,
int name_len,
bool copy_name,
CORE_ADDR address,
enum minimal_symbol_type ms_type,
int section);
/* Like record_full, but:
- uses strlen to compute NAME_LEN,
- passes COPY_NAME = true,
- and passes a default SECTION, depending on the type
This variant does not return the new symbol. */
void record (const char *name, CORE_ADDR address,
enum minimal_symbol_type ms_type);
/* Like record_full, but:
- uses strlen to compute NAME_LEN,
- passes COPY_NAME = true. */
struct minimal_symbol *record_with_info (const char *name,
CORE_ADDR address,
enum minimal_symbol_type ms_type,
int section)
{
return record_full (name, strlen (name), true, address, ms_type, section);
}
private:
/* No need for these. They are intentionally not defined anywhere. */
minimal_symbol_reader &operator=
(const minimal_symbol_reader &);
minimal_symbol_reader (const minimal_symbol_reader &);
struct objfile *m_objfile;
/* Bunch currently being filled up.
The next field points to chain of filled bunches. */
struct msym_bunch *m_msym_bunch;
/* Number of slots filled in current bunch. */
int m_msym_bunch_index;
/* Total number of minimal symbols recorded so far for the
objfile. */
int m_msym_count;
};
/* Create the terminating entry of OBJFILE's minimal symbol table.
If OBJFILE->msymbols is zero, allocate a single entry from
OBJFILE->objfile_obstack; otherwise, just initialize
OBJFILE->msymbols[OBJFILE->minimal_symbol_count]. */
void terminate_minimal_symbol_table (struct objfile *objfile);
/* Return whether MSYMBOL is a function/method. */
bool msymbol_is_text (minimal_symbol *msymbol);
/* Compute a hash code for the string argument. */
unsigned int msymbol_hash (const char *);
/* Like msymbol_hash, but compute a hash code that is compatible with
strcmp_iw. */
unsigned int msymbol_hash_iw (const char *);
/* Compute the next hash value from previous HASH and the character C. This
is only a GDB in-memory computed value with no external files compatibility
requirements. */
#define SYMBOL_HASH_NEXT(hash, c) \
((hash) * 67 + tolower ((unsigned char) (c)) - 113)
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME. If OBJF is non-NULL, limit
the search to that objfile. If SFILE is non-NULL, the only
file-scope symbols considered will be from that source file (global
symbols are still preferred). Returns a bound minimal symbol that
matches, or an empty bound minimal symbol if no match is found. */
struct bound_minimal_symbol lookup_minimal_symbol (const char *,
const char *,
struct objfile *);
/* Like lookup_minimal_symbol, but searches all files and
objfiles. */
struct bound_minimal_symbol lookup_bound_minimal_symbol (const char *);
/* Find the minimal symbol named NAME, and return both the minsym
struct and its objfile. This only checks the linkage name. */
struct bound_minimal_symbol lookup_minimal_symbol_and_objfile (const char *);
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME and has text type. If OBJF
is non-NULL, limit the search to that objfile. Returns a bound
minimal symbol that matches, or an "empty" bound minimal symbol
otherwise.
This function only searches the mangled (linkage) names. */
struct bound_minimal_symbol lookup_minimal_symbol_text (const char *,
struct objfile *);
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME and is a solib trampoline.
If OBJF is non-NULL, limit the search to that objfile. Returns a
pointer to the minimal symbol that matches, or NULL if no match is
found.
This function only searches the mangled (linkage) names. */
struct bound_minimal_symbol lookup_minimal_symbol_solib_trampoline
(const char *,
struct objfile *);
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME and PC. If OBJF is non-NULL,
limit the search to that objfile. Returns a pointer to the minimal
symbol that matches, or NULL if no match is found. */
struct minimal_symbol *lookup_minimal_symbol_by_pc_name
(CORE_ADDR, const char *, struct objfile *);
/* Search through the minimal symbol table for each objfile and find
the symbol whose address is the largest address that is still less
than or equal to PC, and which matches SECTION.
If SECTION is NULL, this uses the result of find_pc_section
instead.
The result has a non-NULL 'minsym' member if such a symbol is
found, or NULL if PC is not in a suitable range. */
struct bound_minimal_symbol lookup_minimal_symbol_by_pc_section
(CORE_ADDR,
struct obj_section *);
/* Backward compatibility: search through the minimal symbol table
for a matching PC (no section given).
This is a wrapper that calls lookup_minimal_symbol_by_pc_section
with a NULL section argument. */
struct bound_minimal_symbol lookup_minimal_symbol_by_pc (CORE_ADDR);
/* Iterate over all the minimal symbols in the objfile OBJF which
match NAME. Both the ordinary and demangled names of each symbol
are considered. The caller is responsible for canonicalizing NAME,
should that need to be done.
For each matching symbol, CALLBACK is called with the symbol and
USER_DATA as arguments. */
void iterate_over_minimal_symbols (struct objfile *objf,
const char *name,
void (*callback) (struct minimal_symbol *,
void *),
void *user_data);
/* Compute the upper bound of MINSYM. The upper bound is the last
address thought to be part of the symbol. If the symbol has a
size, it is used. Otherwise use the lesser of the next minimal
symbol in the same section, or the end of the section, as the end
of the function. */
CORE_ADDR minimal_symbol_upper_bound (struct bound_minimal_symbol minsym);
/* Return the type of MSYMBOL, a minimal symbol of OBJFILE. If
ADDRESS_P is not NULL, set it to the MSYMBOL's resolved
address. */
type *find_minsym_type_and_address (minimal_symbol *msymbol, objfile *objf,
CORE_ADDR *address_p);
#endif /* MINSYMS_H */
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