Pedro Alves c973d0aa4a Fix type casts losing typedefs and reimplement "whatis" typedef stripping
(Ref: https://sourceware.org/ml/gdb/2017-06/msg00020.html)

Assuming int_t is a typedef to int:

 typedef int int_t;

gdb currently loses this expression's typedef:

 (gdb) p (int_t) 0
 $1 = 0
 (gdb) whatis $1
 type = int

or:

 (gdb) whatis (int_t) 0
 type = int

or, to get "whatis" out of the way:

 (gdb) maint print type (int_t) 0
 ...
 name 'int'
 code 0x8 (TYPE_CODE_INT)
 ...

This prevents a type printer for "int_t" kicking in, with e.g.:

 (gdb) p (int_t) 0

From the manual, we can see that that "whatis (int_t) 0" command
invocation should have printed "type = int_t":

 If @var{arg} is a variable or an expression, @code{whatis} prints its
 literal type as it is used in the source code.  If the type was
 defined using a @code{typedef}, @code{whatis} will @emph{not} print
 the data type underlying the @code{typedef}.
 (...)
 If @var{arg} is a type name that was defined using @code{typedef},
 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.

That one-level stripping is currently done here, in
gdb/eval.c:evaluate_subexp_standard, handling OP_TYPE:

...
     else if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  struct type *type = exp->elts[pc + 1].type;

	  /* If this is a typedef, then find its immediate target.  We
	     use check_typedef to resolve stubs, but we ignore its
	     result because we do not want to dig past all
	     typedefs.  */
	  check_typedef (type);
	  if (TYPE_CODE (type) == TYPE_CODE_TYPEDEF)
	    type = TYPE_TARGET_TYPE (type);
	  return allocate_value (type);
	}

However, this stripping is reachable in both:

  - (gdb) whatis (int_t)0     # ARG is an expression with a cast to
                                # typedef type.
  - (gdb) whatis int_t        # ARG is a type name.

while only case  should strip the typedef.  Removing that code from
evaluate_subexp_standard is part of the fix.  Instead, we make the
"whatis" command implementation itself strip one level of typedefs
when the command argument is a type name.

We then run into another problem, also fixed by this commit:
value_cast always drops any typedefs of the destination type.

With all that fixed, "whatis (int_t) 0" now works as expected:

 (gdb) whatis int_t
 type = int
 (gdb) whatis (int_t)0
 type = int_t

value_cast has many different exit/convertion paths, for handling many
different kinds of casts/conversions, and most of them had to be
tweaked to construct the value of the right "to" type.  The new tests
try to exercise most of it, by trying castin of many different
combinations of types.  With:

 $ make check TESTS="*/whatis-ptype*.exp */gnu_vector.exp */dfp-test.exp"

... due to combinatorial explosion, the testsuite results for the
tests above alone grow like:

 - # of expected passes            246
 + # of expected passes            3811

You'll note that the tests exposed one GCC buglet, filed here:

  Missing DW_AT_type in DW_TAG_typedef of "typedef of typedef of void"
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81267

gdb/ChangeLog:
2017-08-21  Pedro Alves  <palves@redhat.com>

	* eval.c (evaluate_subexp_standard) <OP_TYPE>: Don't dig past
	typedefs.
	* typeprint.c (whatis_exp): If handling "whatis", and expression
	is OP_TYPE, strip one typedef level.  Otherwise don't strip
	typedefs here.
	* valops.c (value_cast): Save "to" type before resolving
	stubs/typedefs.  Use that type as resulting value's type.

gdb/testsuite/ChangeLog:
2017-08-21  Pedro Alves  <palves@redhat.com>

	* gdb.base/dfp-test.c
	(d32_t, d64_t, d128_t, d32_t2, d64_t2, d128_t2, v_d32_t, v_d64_t)
	(v_d128_t, v_d32_t2, v_d64_t2, v_d128_t2): New.
	* gdb.base/dfp-test.exp: Add whatis/ptype/cast tests.
	* gdb.base/gnu_vector.exp: Add whatis/ptype/cast tests.
	* gdb.base/whatis-ptype-typedefs.c: New.
	* gdb.base/whatis-ptype-typedefs.exp: New.
	* gdb.python/py-prettyprint.c (int_type, int_type2): New typedefs.
	(an_int, an_int_type, an_int_type2): New globals.
	* gdb.python/py-prettyprint.exp (run_lang_tests): Add tests
	involving typedefs and cast expressions.
	* gdb.python/py-prettyprint.py (class pp_int_typedef): New.
	(lookup_typedefs_function): New.
	(typedefs_pretty_printers_dict): New.
	(top level): Register lookup_typedefs_function in
	gdb.pretty_printers.
2017-08-21 11:34:32 +01:00

370 lines
5.9 KiB
C

/* This testcase is part of GDB, the GNU debugger.
Copyright 2008-2017 Free Software Foundation, Inc.
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 <string.h>
struct s
{
int a;
int *b;
};
struct ss
{
struct s a;
struct s b;
};
struct arraystruct
{
int y;
struct s x[2];
};
struct ns {
const char *null_str;
int length;
};
struct lazystring {
const char *lazy_str;
/* If -1, don't pass length to gdb.lazy_string(). */
int len;
};
struct hint_error {
int x;
};
struct children_as_list {
int x;
};
#ifdef __cplusplus
struct S : public s {
int zs;
};
struct SS {
int zss;
S s;
};
struct SSS
{
SSS (int x, const S& r);
int a;
const S &b;
};
SSS::SSS (int x, const S& r) : a(x), b(r) { }
class VirtualTest
{
private:
int value;
public:
VirtualTest ()
{
value = 1;
}
};
class Vbase1 : public virtual VirtualTest { };
class Vbase2 : public virtual VirtualTest { };
class Vbase3 : public virtual VirtualTest { };
class Derived : public Vbase1, public Vbase2, public Vbase3
{
private:
int value;
public:
Derived ()
{
value = 2;
}
};
class Fake
{
int sname;
public:
Fake (const int name = 0):
sname (name)
{
}
};
#endif
struct substruct {
int a;
int b;
};
struct outerstruct {
struct substruct s;
int x;
};
struct outerstruct
substruct_test (void)
{
struct outerstruct outer;
outer.s.a = 0;
outer.s.b = 0;
outer.x = 0;
outer.s.a = 3; /* MI outer breakpoint here */
return outer;
}
typedef struct string_repr
{
struct whybother
{
const char *contents;
} whybother;
} string;
/* This lets us avoid malloc. */
int array[100];
int narray[10];
struct justchildren
{
int len;
int *elements;
};
typedef struct justchildren nostring_type;
struct memory_error
{
const char *s;
};
struct container
{
string name;
int len;
int *elements;
};
typedef struct container zzz_type;
string
make_string (const char *s)
{
string result;
result.whybother.contents = s;
return result;
}
zzz_type
make_container (const char *s)
{
zzz_type result;
result.name = make_string (s);
result.len = 0;
result.elements = 0;
return result;
}
void
add_item (zzz_type *c, int val)
{
if (c->len == 0)
c->elements = array;
c->elements[c->len] = val;
++c->len;
}
void
set_item(zzz_type *c, int i, int val)
{
if (i < c->len)
c->elements[i] = val;
}
void init_s(struct s *s, int a)
{
s->a = a;
s->b = &s->a;
}
void init_ss(struct ss *s, int a, int b)
{
init_s(&s->a, a);
init_s(&s->b, b);
}
void do_nothing(void)
{
int c;
c = 23; /* Another MI breakpoint */
}
struct nullstr
{
char *s;
};
struct string_repr string_1 = { { "one" } };
struct string_repr string_2 = { { "two" } };
int
eval_func (int p1, int p2, int p3, int p4, int p5, int p6, int p7, int p8)
{
return p1;
}
static void
eval_sub (void)
{
struct eval_type_s { int x; } eval1 = { 1 }, eval2 = { 2 }, eval3 = { 3 },
eval4 = { 4 }, eval5 = { 5 }, eval6 = { 6 },
eval7 = { 7 }, eval8 = { 8 }, eval9 = { 9 };
eval1.x++; /* eval-break */
}
static void
bug_14741()
{
zzz_type c = make_container ("bug_14741");
add_item (&c, 71);
set_item(&c, 0, 42); /* breakpoint bug 14741 */
set_item(&c, 0, 5);
}
/* Some typedefs/variables for checking that GDB doesn't lose typedefs
when looking for a printer. */
typedef int int_type;
typedef int_type int_type2;
int an_int = -1;
int_type an_int_type = 1;
int_type2 an_int_type2 = 2;
int
main ()
{
struct ss ss;
struct ss ssa[2];
struct arraystruct arraystruct;
string x = make_string ("this is x");
zzz_type c = make_container ("container");
zzz_type c2 = make_container ("container2");
const struct string_repr cstring = { { "const string" } };
/* Clearing by being `static' could invoke an other GDB C++ bug. */
struct nullstr nullstr;
nostring_type nstype, nstype2;
struct memory_error me;
struct ns ns, ns2;
struct lazystring estring, estring2, estring3;
struct hint_error hint_error;
struct children_as_list children_as_list;
nstype.elements = narray;
nstype.len = 0;
me.s = "blah";
init_ss(&ss, 1, 2);
init_ss(ssa+0, 3, 4);
init_ss(ssa+1, 5, 6);
memset (&nullstr, 0, sizeof nullstr);
arraystruct.y = 7;
init_s (&arraystruct.x[0], 23);
init_s (&arraystruct.x[1], 24);
ns.null_str = "embedded\0null\0string";
ns.length = 20;
/* Make a "corrupted" string. */
ns2.null_str = NULL;
ns2.length = 20;
estring.lazy_str = "embedded x\201\202\203\204";
estring.len = -1;
/* Incomplete UTF-8, but ok Latin-1. */
estring2.lazy_str = "embedded x\302";
estring2.len = -1;
estring3.lazy_str = NULL;
estring3.len = 42;
#ifdef __cplusplus
S cps;
cps.zs = 7;
init_s(&cps, 8);
SS cpss;
cpss.zss = 9;
init_s(&cpss.s, 10);
SS cpssa[2];
cpssa[0].zss = 11;
init_s(&cpssa[0].s, 12);
cpssa[1].zss = 13;
init_s(&cpssa[1].s, 14);
SSS sss(15, cps);
SSS& ref (sss);
Derived derived;
Fake fake (42);
#endif
add_item (&c, 23); /* MI breakpoint here */
add_item (&c, 72);
#ifdef MI
add_item (&c, 1011);
c.elements[0] = 1023;
c.elements[0] = 2323;
add_item (&c2, 2222);
add_item (&c2, 3333);
substruct_test ();
do_nothing ();
#endif
nstype.elements[0] = 7;
nstype.elements[1] = 42;
nstype.len = 2;
nstype2 = nstype;
eval_sub ();
bug_14741(); /* break to inspect struct and union */
return 0;
}