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binutils-gdb/gdb/compile/compile-cplus-symbols.c
Pedro Alves 04902b0995 Rewrite enum_flags, add unit tests, fix problems 
This patch started by adding comprehensive unit tests for enum_flags.

For the testing part, it adds:

 - tests of normal expected uses of the API.

 - checks that _invalid_ uses of the API would fail to compile.  I.e.,
   it validates that enum_flags really is a strong type, and that
   incorrect mixing of enum types would be caught at compile time.  It
   pulls that off making use of SFINEA and C++11's decltype/constexpr.

This revealed many holes in the enum_flags API.  For example, the f1
assignment below currently incorrectly fails to compile:

 enum_flags<flags> f1 = FLAG1;
 enum_flags<flags> f2 = FLAG2 | f1;

The unit tests also revealed that this useful use case doesn't work:

    enum flag { FLAG1 = 1, FLAG2 = 2 };
    enum_flags<flag> src = FLAG1;
    enum_flags<flag> f1 = condition ? src : FLAG2;

It fails to compile because enum_flags<flag> and flag are convertible
to each other.

Turns out that making enum_flags be implicitly convertible to the
backing raw enum type was not a good idea.

If we make it convertible to the underlying type instead, we fix that
ternary operator use case, and, we find cases throughout the codebase
that should be using the enum_flags but were using the raw backing
enum instead.  So it's a good change overall.

Also, several operators were missing.

These holes and more are plugged by this patch, by reworking how the
enum_flags operators are implemented, and making use of C++11's
feature of being able to delete methods/functions.

There are cases in gdb/compile/ where we need to call a function in a
C plugin API that expects the raw enum.  To address cases like that,
this adds a "raw()" method to enum_flags.  This way we can keep using
the safer enum_flags to construct the value, and then be explicit when
we need to get at the raw enum.

This makes most of the enum_flags operators constexpr.  Beyond
enabling more compiler optimizations and enabling the new unit tests,
this has other advantages, like making it possible to use operator|
with enum_flags values in switch cases, where only compile-time
constants are allowed:

    enum_flags<flags> f = FLAG1 | FLAG2;
    switch (f)
      {
      case FLAG1 | FLAG2:
	break;
      }

Currently that fails to compile.

It also switches to a different mechanism of enabling the global
operators.  The current mechanism isn't namespace friendly, the new
one is.

It also switches to C++11-style SFINAE -- instead of wrapping the
return type in a SFINAE-friently structure, we use an unnamed template
parameter.  I.e., this:

  template <typename enum_type,
	    typename = is_enum_flags_enum_type_t<enum_type>>
  enum_type
  operator& (enum_type e1, enum_type e2)

instead of:

  template <typename enum_type>
  typename enum_flags_type<enum_type>::type
  operator& (enum_type e1, enum_type e2)

Note that the static_assert inside operator~() was converted to a
couple overloads (signed vs unsigned), because static_assert is too
late for SFINAE-based tests, which is important for the CHECK_VALID
unit tests.

Tested with gcc {4.8, 7.1, 9.3} and clang {5.0.2, 10.0.0}.

gdb/ChangeLog:

	* Makefile.in (SELFTESTS_SRCS): Add
	unittests/enum-flags-selftests.c.
	* btrace.c (ftrace_update_caller, ftrace_fixup_calle): Use
	btrace_function_flags instead of enum btrace_function_flag.
	* compile/compile-c-types.c (convert_qualified): Use
	enum_flags::raw.
	* compile/compile-cplus-symbols.c (convert_one_symbol)
	(convert_symbol_bmsym):
	* compile/compile-cplus-types.c (compile_cplus_convert_method)
	(compile_cplus_convert_struct_or_union_methods)
	(compile_cplus_instance::convert_qualified_base):
	* go-exp.y (parse_string_or_char): Add cast to int.
	* unittests/enum-flags-selftests.c: New file.
	* record-btrace.c (btrace_thread_flag_to_str): Change parameter's
	type to btrace_thread_flags from btrace_thread_flag.
	(record_btrace_cancel_resume, record_btrace_step_thread): Change
	local's type to btrace_thread_flags from btrace_thread_flag.  Add
	cast in DEBUG call.

gdbsupport/ChangeLog:

	* enum-flags.h: Include "traits.h".
	(DEF_ENUM_FLAGS_TYPE): Declare a function instead of defining a
	structure.
	(enum_underlying_type): Update comment.
	(namespace enum_flags_detail): New.  Move struct zero_type here.
	(EnumIsUnsigned, EnumIsSigned): New.
	(class enum_flags): Make most methods constexpr.
	(operator&=, operator|=, operator^=): Take an enum_flags instead
	of an enum_type.  Make rvalue ref versions deleted.
	(operator enum_type()): Delete.
	(operator&, operator|, operator^, operator~): Delete, moved out of
	class.
	(raw()): New method.
	(is_enum_flags_enum_type_t): Declare.
	(ENUM_FLAGS_GEN_BINOP, ENUM_FLAGS_GEN_COMPOUND_ASSIGN)
	(ENUM_FLAGS_GEN_COMP): New.  Use them to reimplement global
	operators.
	(operator~): Now constexpr and reimplemented.
	(operator<<, operator>>): New deleted functions.
	* valid-expr.h (CHECK_VALID_EXPR_5, CHECK_VALID_EXPR_6): New.
2020-09-14 22:21:07 +01:00

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/* Convert symbols from GDB to GCC
Copyright (C) 2014-2020 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/>. */
#include "defs.h"
#include "compile-internal.h"
#include "compile-cplus.h"
#include "gdbsupport/gdb_assert.h"
#include "symtab.h"
#include "parser-defs.h"
#include "block.h"
#include "objfiles.h"
#include "compile.h"
#include "value.h"
#include "exceptions.h"
#include "gdbtypes.h"
#include "dwarf2/loc.h"
#include "cp-support.h"
#include "gdbcmd.h"
#include "compile-c.h"
/* Convert a given symbol, SYM, to the compiler's representation.
INSTANCE is the compiler instance. IS_GLOBAL is true if the
symbol came from the global scope. IS_LOCAL is true if the symbol
came from a local scope. (Note that the two are not strictly
inverses because the symbol might have come from the static
scope.) */
static void
convert_one_symbol (compile_cplus_instance *instance,
struct block_symbol sym, bool is_global, bool is_local)
{
/* Squash compiler warning. */
gcc_type sym_type = 0;
const char *filename = symbol_symtab (sym.symbol)->filename;
unsigned short line = SYMBOL_LINE (sym.symbol);
instance->error_symbol_once (sym.symbol);
if (SYMBOL_CLASS (sym.symbol) == LOC_LABEL)
sym_type = 0;
else
sym_type = instance->convert_type (SYMBOL_TYPE (sym.symbol));
if (SYMBOL_DOMAIN (sym.symbol) == STRUCT_DOMAIN)
{
/* Nothing to do. */
}
else
{
/* Squash compiler warning. */
gcc_cp_symbol_kind_flags kind = GCC_CP_FLAG_BASE;
CORE_ADDR addr = 0;
std::string name;
gdb::unique_xmalloc_ptr<char> symbol_name;
switch (SYMBOL_CLASS (sym.symbol))
{
case LOC_TYPEDEF:
if (SYMBOL_TYPE (sym.symbol)->code () == TYPE_CODE_TYPEDEF)
kind = GCC_CP_SYMBOL_TYPEDEF;
else if (SYMBOL_TYPE (sym.symbol)->code () == TYPE_CODE_NAMESPACE)
return;
break;
case LOC_LABEL:
kind = GCC_CP_SYMBOL_LABEL;
addr = SYMBOL_VALUE_ADDRESS (sym.symbol);
break;
case LOC_BLOCK:
{
kind = GCC_CP_SYMBOL_FUNCTION;
addr = BLOCK_START (SYMBOL_BLOCK_VALUE (sym.symbol));
if (is_global && SYMBOL_TYPE (sym.symbol)->is_gnu_ifunc ())
addr = gnu_ifunc_resolve_addr (target_gdbarch (), addr);
}
break;
case LOC_CONST:
if (SYMBOL_TYPE (sym.symbol)->code () == TYPE_CODE_ENUM)
{
/* Already handled by convert_enum. */
return;
}
instance->plugin ().build_constant
(sym_type, sym.symbol->natural_name (),
SYMBOL_VALUE (sym.symbol), filename, line);
return;
case LOC_CONST_BYTES:
error (_("Unsupported LOC_CONST_BYTES for symbol \"%s\"."),
sym.symbol->print_name ());
case LOC_UNDEF:
internal_error (__FILE__, __LINE__, _("LOC_UNDEF found for \"%s\"."),
sym.symbol->print_name ());
case LOC_COMMON_BLOCK:
error (_("Fortran common block is unsupported for compilation "
"evaluaton of symbol \"%s\"."),
sym.symbol->print_name ());
case LOC_OPTIMIZED_OUT:
error (_("Symbol \"%s\" cannot be used for compilation evaluation "
"as it is optimized out."),
sym.symbol->print_name ());
case LOC_COMPUTED:
if (is_local)
goto substitution;
/* Probably TLS here. */
warning (_("Symbol \"%s\" is thread-local and currently can only "
"be referenced from the current thread in "
"compiled code."),
sym.symbol->print_name ());
/* FALLTHROUGH */
case LOC_UNRESOLVED:
/* 'symbol_name' cannot be used here as that one is used only for
local variables from compile_dwarf_expr_to_c.
Global variables can be accessed by GCC only by their address, not
by their name. */
{
struct value *val;
struct frame_info *frame = nullptr;
if (symbol_read_needs_frame (sym.symbol))
{
frame = get_selected_frame (nullptr);
if (frame == nullptr)
error (_("Symbol \"%s\" cannot be used because "
"there is no selected frame"),
sym.symbol->print_name ());
}
val = read_var_value (sym.symbol, sym.block, frame);
if (VALUE_LVAL (val) != lval_memory)
error (_("Symbol \"%s\" cannot be used for compilation "
"evaluation as its address has not been found."),
sym.symbol->print_name ());
kind = GCC_CP_SYMBOL_VARIABLE;
addr = value_address (val);
}
break;
case LOC_REGISTER:
case LOC_ARG:
case LOC_REF_ARG:
case LOC_REGPARM_ADDR:
case LOC_LOCAL:
substitution:
kind = GCC_CP_SYMBOL_VARIABLE;
symbol_name = c_symbol_substitution_name (sym.symbol);
break;
case LOC_STATIC:
kind = GCC_CP_SYMBOL_VARIABLE;
addr = SYMBOL_VALUE_ADDRESS (sym.symbol);
break;
case LOC_FINAL_VALUE:
default:
gdb_assert_not_reached ("Unreachable case in convert_one_symbol.");
}
/* Don't emit local variable decls for a raw expression. */
if (instance->scope () != COMPILE_I_RAW_SCOPE || symbol_name == nullptr)
{
/* For non-local symbols, create/push a new scope so that the
symbol is properly scoped to the plug-in. */
if (!is_local)
{
compile_scope scope
= instance->new_scope (sym.symbol->natural_name (),
SYMBOL_TYPE (sym.symbol));
if (scope.nested_type () != GCC_TYPE_NONE)
{
/* We found a symbol for this type that was defined inside
some other symbol, e.g., a class typedef defined. */
return;
}
instance->enter_scope (std::move (scope));
}
/* Get the `raw' name of the symbol. */
if (name.empty () && sym.symbol->natural_name () != nullptr)
name = compile_cplus_instance::decl_name
(sym.symbol->natural_name ()).get ();
/* Define the decl. */
instance->plugin ().build_decl
("variable", name.c_str (), kind.raw (), sym_type,
symbol_name.get (), addr, filename, line);
/* Pop scope for non-local symbols. */
if (!is_local)
instance->leave_scope ();
}
}
}
/* Convert a full symbol to its gcc form. CONTEXT is the compiler to
use, IDENTIFIER is the name of the symbol, SYM is the symbol
itself, and DOMAIN is the domain which was searched. */
static void
convert_symbol_sym (compile_cplus_instance *instance,
const char *identifier, struct block_symbol sym,
domain_enum domain)
{
/* If we found a symbol and it is not in the static or global
scope, then we should first convert any static or global scope
symbol of the same name. This lets this unusual case work:
int x; // Global.
int func(void)
{
int x;
// At this spot, evaluate "extern int x; x"
}
*/
const struct block *static_block = block_static_block (sym.block);
/* STATIC_BLOCK is NULL if FOUND_BLOCK is the global block. */
bool is_local_symbol = (sym.block != static_block && static_block != nullptr);
if (is_local_symbol)
{
struct block_symbol global_sym;
global_sym = lookup_symbol (identifier, nullptr, domain, nullptr);
/* If the outer symbol is in the static block, we ignore it, as
it cannot be referenced. */
if (global_sym.symbol != nullptr
&& global_sym.block != block_static_block (global_sym.block))
{
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"gcc_convert_symbol \"%s\": global symbol\n",
identifier);
convert_one_symbol (instance, global_sym, true, false);
}
}
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"gcc_convert_symbol \"%s\": local symbol\n",
identifier);
convert_one_symbol (instance, sym, false, is_local_symbol);
}
/* Convert a minimal symbol to its gcc form. CONTEXT is the compiler
to use and BMSYM is the minimal symbol to convert. */
static void
convert_symbol_bmsym (compile_cplus_instance *instance,
struct bound_minimal_symbol bmsym)
{
struct minimal_symbol *msym = bmsym.minsym;
struct objfile *objfile = bmsym.objfile;
struct type *type;
gcc_cp_symbol_kind_flags kind;
gcc_type sym_type;
CORE_ADDR addr;
addr = MSYMBOL_VALUE_ADDRESS (objfile, msym);
/* Conversion copied from write_exp_msymbol. */
switch (MSYMBOL_TYPE (msym))
{
case mst_text:
case mst_file_text:
case mst_solib_trampoline:
type = objfile_type (objfile)->nodebug_text_symbol;
kind = GCC_CP_SYMBOL_FUNCTION;
break;
case mst_text_gnu_ifunc:
/* nodebug_text_gnu_ifunc_symbol would cause:
function return type cannot be function */
type = objfile_type (objfile)->nodebug_text_symbol;
kind = GCC_CP_SYMBOL_FUNCTION;
addr = gnu_ifunc_resolve_addr (target_gdbarch (), addr);
break;
case mst_data:
case mst_file_data:
case mst_bss:
case mst_file_bss:
type = objfile_type (objfile)->nodebug_data_symbol;
kind = GCC_CP_SYMBOL_VARIABLE;
break;
case mst_slot_got_plt:
type = objfile_type (objfile)->nodebug_got_plt_symbol;
kind = GCC_CP_SYMBOL_FUNCTION;
break;
default:
type = objfile_type (objfile)->nodebug_unknown_symbol;
kind = GCC_CP_SYMBOL_VARIABLE;
break;
}
sym_type = instance->convert_type (type);
instance->plugin ().push_namespace ("");
instance->plugin ().build_decl
("minsym", msym->natural_name (), kind.raw (), sym_type, nullptr, addr,
nullptr, 0);
instance->plugin ().pop_binding_level ("");
}
/* See compile-cplus.h. */
void
gcc_cplus_convert_symbol (void *datum,
struct gcc_cp_context *gcc_context,
enum gcc_cp_oracle_request request,
const char *identifier)
{
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"got oracle request for \"%s\"\n", identifier);
bool found = false;
compile_cplus_instance *instance = (compile_cplus_instance *) datum;
try
{
/* Symbol searching is a three part process unfortunately. */
/* First do a "standard" lookup, converting any found symbols.
This will find variables in the current scope. */
struct block_symbol sym
= lookup_symbol (identifier, instance->block (), VAR_DOMAIN, nullptr);
if (sym.symbol != nullptr)
{
found = true;
convert_symbol_sym (instance, identifier, sym, VAR_DOMAIN);
}
/* Then use linespec.c's multi-symbol search. This should find
all non-variable symbols for which we have debug info. */
symbol_searcher searcher;
searcher.find_all_symbols (identifier, current_language,
ALL_DOMAIN, nullptr, nullptr);
/* Convert any found symbols. */
for (const auto &it : searcher.matching_symbols ())
{
/* Don't convert the symbol found above, if any, twice! */
if (it.symbol != sym.symbol)
{
found = true;
convert_symbol_sym (instance, identifier, it,
SYMBOL_DOMAIN (it.symbol));
}
}
/* Finally, if no symbols have been found, fall back to minsyms. */
if (!found)
{
for (const auto &it : searcher.matching_msymbols ())
{
found = true;
convert_symbol_bmsym (instance, it);
}
}
}
catch (const gdb_exception &e)
{
/* We can't allow exceptions to escape out of this callback. Safest
is to simply emit a gcc error. */
instance->plugin ().error (e.what ());
}
if (compile_debug && !found)
fprintf_unfiltered (gdb_stdlog,
"gcc_convert_symbol \"%s\": lookup_symbol failed\n",
identifier);
if (compile_debug)
{
if (found)
fprintf_unfiltered (gdb_stdlog, "found type for %s\n", identifier);
else
{
fprintf_unfiltered (gdb_stdlog, "did not find type for %s\n",
identifier);
}
}
return;
}
/* See compile-cplus.h. */
gcc_address
gcc_cplus_symbol_address (void *datum, struct gcc_cp_context *gcc_context,
const char *identifier)
{
compile_cplus_instance *instance = (compile_cplus_instance *) datum;
gcc_address result = 0;
int found = 0;
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"got oracle request for address of %s\n", identifier);
/* We can't allow exceptions to escape out of this callback. Safest
is to simply emit a gcc error. */
try
{
struct symbol *sym
= lookup_symbol (identifier, nullptr, VAR_DOMAIN, nullptr).symbol;
if (sym != nullptr && SYMBOL_CLASS (sym) == LOC_BLOCK)
{
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"gcc_symbol_address \"%s\": full symbol\n",
identifier);
result = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
if (SYMBOL_TYPE (sym)->is_gnu_ifunc ())
result = gnu_ifunc_resolve_addr (target_gdbarch (), result);
found = 1;
}
else
{
struct bound_minimal_symbol msym;
msym = lookup_bound_minimal_symbol (identifier);
if (msym.minsym != nullptr)
{
if (compile_debug)
fprintf_unfiltered (gdb_stdlog,
"gcc_symbol_address \"%s\": minimal "
"symbol\n",
identifier);
result = BMSYMBOL_VALUE_ADDRESS (msym);
if (MSYMBOL_TYPE (msym.minsym) == mst_text_gnu_ifunc)
result = gnu_ifunc_resolve_addr (target_gdbarch (), result);
found = 1;
}
}
}
catch (const gdb_exception_error &e)
{
instance->plugin ().error (e.what ());
}
if (compile_debug && !found)
fprintf_unfiltered (gdb_stdlog,
"gcc_symbol_address \"%s\": failed\n",
identifier);
if (compile_debug)
{
if (found)
fprintf_unfiltered (gdb_stdlog, "found address for %s!\n", identifier);
else
fprintf_unfiltered (gdb_stdlog,
"did not find address for %s\n", identifier);
}
return result;
}
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