[RFA,v2,2/6] Handle alignof and _Alignof

Message ID 20180427140139.7957-3-tom@tromey.com
State New
Headers show
Series
  • Type alignment
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Commit Message

Tom Tromey April 27, 2018, 2:01 p.m.
This adds alignof and _Alignof to the C/C++ expression parser, and
adds new tests to test the features.  The tests are written to try to
ensure that gdb's knowledge of alignment rules stays in sync with the
compiler's.

2018-04-27  Tom Tromey  <tom@tromey.com>

	PR exp/17095:
	* NEWS: Update.
	* std-operator.def (UNOP_ALIGNOF): New operator.
	* expprint.c (dump_subexp_body_standard) <case UNOP_ALIGNOF>:
	New.
	* eval.c (evaluate_subexp_standard) <case UNOP_ALIGNOF>: New.
	* c-lang.c (c_op_print_tab): Add alignof.
	* c-exp.y (ALIGNOF): New token.
	(exp): Add "ALIGNOF" production.
	(ident_tokens): Add _Alignof and alignof.

2018-04-27  Tom Tromey  <tom@tromey.com>

	PR exp/17095:
	* gdb.dwarf2/dw2-align.exp: New file.
	* gdb.cp/align.exp: New file.
	* gdb.base/align.exp: New file.
---
 gdb/ChangeLog                          |  13 +++
 gdb/NEWS                               |   3 +
 gdb/c-exp.y                            |   8 +-
 gdb/c-lang.c                           |   1 +
 gdb/eval.c                             |  13 +++
 gdb/expprint.c                         |   1 +
 gdb/std-operator.def                   |   1 +
 gdb/testsuite/ChangeLog                |   7 ++
 gdb/testsuite/gdb.base/align.exp       | 101 +++++++++++++++++++++++
 gdb/testsuite/gdb.cp/align.exp         | 145 +++++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.dwarf2/dw2-align.exp |  83 +++++++++++++++++++
 11 files changed, 375 insertions(+), 1 deletion(-)
 create mode 100644 gdb/testsuite/gdb.base/align.exp
 create mode 100644 gdb/testsuite/gdb.cp/align.exp
 create mode 100644 gdb/testsuite/gdb.dwarf2/dw2-align.exp

-- 
2.14.3

Comments

Eli Zaretskii April 27, 2018, 2:18 p.m. | #1
> From: Tom Tromey <tom@tromey.com>

> Cc: Tom Tromey <tom@tromey.com>

> Date: Fri, 27 Apr 2018 08:01:35 -0600

> 

> diff --git a/gdb/NEWS b/gdb/NEWS

> index 63fe30d175..6631b53475 100644

> --- a/gdb/NEWS

> +++ b/gdb/NEWS

> @@ -9,6 +9,9 @@

>  * 'info proc' now works on running processes on FreeBSD systems and core

>    files created on FreeBSD systems.

>  

> +* C expressions can now use _Alignof, and C++ expressions can now use

> +  alignof.

> +

>  * New commands


This part is OK, thanks.
Pedro Alves April 27, 2018, 6:46 p.m. | #2
On 04/27/2018 03:01 PM, Tom Tromey wrote:
> This adds alignof and _Alignof to the C/C++ expression parser, and

> adds new tests to test the features.  The tests are written to try to

> ensure that gdb's knowledge of alignment rules stays in sync with the

> compiler's.


This looks good to me.  A few comments on additional tests below,
but there's no need for another round of review for those.

> +++ b/gdb/testsuite/gdb.cp/align.exp

> @@ -0,0 +1,145 @@


...

> +

> +# Prologue.

> +puts $outfile {

> +    template<typename T, typename U>

> +    struct align_pair

> +    {

> +	T one;

> +	U two;

> +    };

> +

> +    template<typename T, typename U>

> +    struct align_union

> +    {

> +	T one;

> +	U two;

> +    };

> +

> +    enum bigenum { VALUE = 0xffffffffull };

> +

> +    struct empty { };

> +

> +    struct vstruct { virtual ~vstruct() {}  char c; };

> +

> +    struct bfstruct { unsigned b : 3; };

> +

> +    struct arrstruct { short fld[7]; };


Sorry to be a drag, but I think it'd be good to add a few
more tests here:

 - alignof(typedef)

   (to make sure we're not missing a check_typedef
   call somewhere.  e.g., add "typedef arrstruct arrstruct_t",
   then add arrstruct_t to the list of tested types.

 - alignof(a class with a base class).

   E.g.,:

    struct A { int i;};
    struct B : A { char c; };

   and then check alignof(B).

   multiple and virtual inheritance might be worth
   testing too, not sure whether the code paths are
   (and will always be) the same.

 - alignof(array-type)

   This is what I actually meant by arrays in v1.  E.g.:

     alignof (int[3])

   It might be we don't parse that.  Not sure.  If it's hard,
   it's ok to punt, but then it'd be good to still add the test
   and kfail it.

> +proc maybe_xfail {type} {

> +    # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560

> +    # The g++ implementation of alignof is changing to match C11.

> +    if {[is_x86_like_target]

> +	&& ($type == "double" || $type == "long long"

> +	    || $type == "unsigned long long")} {

> +	setup_xfail *-*-*


It seems like we can check for gcc version with test_compiler_info.
Maybe go ahead and limit the xfail to:

  [test_compiler_info {gcc-[0-8]-*}]

?

Thanks,
Pedro Alves
Tom Tromey April 27, 2018, 8:55 p.m. | #3
>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:


Pedro>  - alignof(typedef)

Pedro>    (to make sure we're not missing a check_typedef
Pedro>    call somewhere.  e.g., add "typedef arrstruct arrstruct_t",
Pedro>    then add arrstruct_t to the list of tested types.

This one is in the patch already:

+    puts $outfile "typedef $type t_$utype;"
+    puts $outfile "t_$utype item_t_$utype;"
[...]
+    gdb_test "print alignof(t_$utype)" " = $expected"

I'll add the others though.

Tom
Tom Tromey April 27, 2018, 8:59 p.m. | #4
>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:


>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

Pedro> - alignof(typedef)

Pedro> (to make sure we're not missing a check_typedef
Pedro> call somewhere.  e.g., add "typedef arrstruct arrstruct_t",
Pedro> then add arrstruct_t to the list of tested types.

Tom> This one is in the patch already:
[..]


I forgot to mention, but for C++ specifically, there's an issue with
using typedefs as template parameters:

https://sourceware.org/bugzilla/show_bug.cgi?id=23103

... which is why this particular form of the test isn't in there.

Tom
Tom Tromey April 30, 2018, 4:49 p.m. | #5
>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:


Pedro> This looks good to me.  A few comments on additional tests below,
Pedro> but there's no need for another round of review for those.

This patch will need another review since I added some new stuff.

Pedro> Sorry to be a drag, but I think it'd be good to add a few
Pedro> more tests here:

Pedro>  - alignof(typedef)

This was already in there.

Pedro>  - alignof(a class with a base class).

Done.

Pedro>  - alignof(array-type)

Done.

Pedro> Maybe go ahead and limit the xfail to:

Pedro>   [test_compiler_info {gcc-[0-8]-*}]

Done.


This version includes a couple of new gdb_caching_procs to do the
__int128 check.

Tom


commit 16be2868c298498eb936e57943a781701925bed9
Author: Tom Tromey <tom@tromey.com>
Date:   Fri Apr 20 13:40:29 2018 -0600

    Handle alignof and _Alignof
    
    This adds alignof and _Alignof to the C/C++ expression parser, and
    adds new tests to test the features.  The tests are written to try to
    ensure that gdb's knowledge of alignment rules stays in sync with the
    compiler's.
    
    2018-04-27  Tom Tromey  <tom@tromey.com>
    
            PR exp/17095:
            * NEWS: Update.
            * std-operator.def (UNOP_ALIGNOF): New operator.
            * expprint.c (dump_subexp_body_standard) <case UNOP_ALIGNOF>:
            New.
            * eval.c (evaluate_subexp_standard) <case UNOP_ALIGNOF>: New.
            * c-lang.c (c_op_print_tab): Add alignof.
            * c-exp.y (ALIGNOF): New token.
            (exp): Add "ALIGNOF" production.
            (ident_tokens): Add _Alignof and alignof.
    
    2018-04-30  Tom Tromey  <tom@tromey.com>
    
            PR exp/17095:
            * gdb.dwarf2/dw2-align.exp: New file.
            * gdb.cp/align.exp: New file.
            * gdb.base/align.exp: New file.
            * lib/gdb.exp (gdb_int128_helper): New proc.
            (has_int128_c, has_int128_cxx): New caching procs.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9a6952ae62..2a5bf3e603 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,16 @@
+2018-04-27  Tom Tromey  <tom@tromey.com>
+
+	PR exp/17095:
+	* NEWS: Update.
+	* std-operator.def (UNOP_ALIGNOF): New operator.
+	* expprint.c (dump_subexp_body_standard) <case UNOP_ALIGNOF>:
+	New.
+	* eval.c (evaluate_subexp_standard) <case UNOP_ALIGNOF>: New.
+	* c-lang.c (c_op_print_tab): Add alignof.
+	* c-exp.y (ALIGNOF): New token.
+	(exp): Add "ALIGNOF" production.
+	(ident_tokens): Add _Alignof and alignof.
+
 2018-04-27  Tom Tromey  <tom@tromey.com>
 
 	* i386-tdep.c (i386_type_align): New function.
diff --git a/gdb/NEWS b/gdb/NEWS
index 63fe30d175..6631b53475 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -9,6 +9,9 @@
 * 'info proc' now works on running processes on FreeBSD systems and core
   files created on FreeBSD systems.
 
+* C expressions can now use _Alignof, and C++ expressions can now use
+  alignof.
+
 * New commands
 
 set debug fbsd-nat
diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index 9e2f80889f..3cee544106 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -173,7 +173,7 @@ static void c_print_token (FILE *file, int type, YYSTYPE value);
 %token <ssym> NAME_OR_INT
 
 %token OPERATOR
-%token STRUCT CLASS UNION ENUM SIZEOF UNSIGNED COLONCOLON
+%token STRUCT CLASS UNION ENUM SIZEOF ALIGNOF UNSIGNED COLONCOLON
 %token TEMPLATE
 %token ERROR
 %token NEW DELETE
@@ -307,6 +307,10 @@ exp	:	SIZEOF exp       %prec UNARY
 			{ write_exp_elt_opcode (pstate, UNOP_SIZEOF); }
 	;
 
+exp	:	ALIGNOF '(' type_exp ')'	%prec UNARY
+			{ write_exp_elt_opcode (pstate, UNOP_ALIGNOF); }
+	;
+
 exp	:	exp ARROW name
 			{ write_exp_elt_opcode (pstate, STRUCTOP_PTR);
 			  write_exp_string (pstate, $3);
@@ -2329,6 +2333,8 @@ static const struct token ident_tokens[] =
     {"struct", STRUCT, OP_NULL, 0},
     {"signed", SIGNED_KEYWORD, OP_NULL, 0},
     {"sizeof", SIZEOF, OP_NULL, 0},
+    {"_Alignof", ALIGNOF, OP_NULL, 0},
+    {"alignof", ALIGNOF, OP_NULL, FLAG_CXX},
     {"double", DOUBLE_KEYWORD, OP_NULL, 0},
     {"false", FALSEKEYWORD, OP_NULL, FLAG_CXX},
     {"class", CLASS, OP_NULL, FLAG_CXX},
diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index 658c7f7826..15e633f8c8 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -751,6 +751,7 @@ const struct op_print c_op_print_tab[] =
   {"*", UNOP_IND, PREC_PREFIX, 0},
   {"&", UNOP_ADDR, PREC_PREFIX, 0},
   {"sizeof ", UNOP_SIZEOF, PREC_PREFIX, 0},
+  {"alignof ", UNOP_ALIGNOF, PREC_PREFIX, 0},
   {"++", UNOP_PREINCREMENT, PREC_PREFIX, 0},
   {"--", UNOP_PREDECREMENT, PREC_PREFIX, 0},
   {NULL, OP_NULL, PREC_PREFIX, 0}
diff --git a/gdb/eval.c b/gdb/eval.c
index ad66f7c32c..2fdfdf9353 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -2667,6 +2667,19 @@ evaluate_subexp_standard (struct type *expect_type,
 	}
       return evaluate_subexp_for_sizeof (exp, pos, noside);
 
+    case UNOP_ALIGNOF:
+      {
+	struct type *type
+	  = value_type (evaluate_subexp (NULL_TYPE, exp, pos,
+					 EVAL_AVOID_SIDE_EFFECTS));
+	/* FIXME: This should be size_t.  */
+	struct type *size_type = builtin_type (exp->gdbarch)->builtin_int;
+	ULONGEST align = type_align (type);
+	if (align == 0)
+	  error (_("could not determine alignment of type"));
+	return value_from_longest (size_type, align);
+      }
+
     case UNOP_CAST:
       (*pos) += 2;
       type = exp->elts[pc + 1].type;
diff --git a/gdb/expprint.c b/gdb/expprint.c
index 047ec11df1..70d355d369 100644
--- a/gdb/expprint.c
+++ b/gdb/expprint.c
@@ -850,6 +850,7 @@ dump_subexp_body_standard (struct expression *exp,
     case UNOP_PREDECREMENT:
     case UNOP_POSTDECREMENT:
     case UNOP_SIZEOF:
+    case UNOP_ALIGNOF:
     case UNOP_PLUS:
     case UNOP_CAP:
     case UNOP_CHR:
diff --git a/gdb/std-operator.def b/gdb/std-operator.def
index 87bb518877..1297c1edeb 100644
--- a/gdb/std-operator.def
+++ b/gdb/std-operator.def
@@ -234,6 +234,7 @@ OP (UNOP_POSTINCREMENT)		/* ++ after an expression */
 OP (UNOP_PREDECREMENT)		/* -- before an expression */
 OP (UNOP_POSTDECREMENT)		/* -- after an expression */
 OP (UNOP_SIZEOF)		/* Unary sizeof (followed by expression) */
+OP (UNOP_ALIGNOF)		/* Unary alignof (followed by expression) */
 
 OP (UNOP_PLUS)			/* Unary plus */
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 22cf4ff47a..e8b55aac90 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2018-04-30  Tom Tromey  <tom@tromey.com>
+
+	PR exp/17095:
+	* gdb.dwarf2/dw2-align.exp: New file.
+	* gdb.cp/align.exp: New file.
+	* gdb.base/align.exp: New file.
+	* lib/gdb.exp (gdb_int128_helper): New proc.
+	(has_int128_c, has_int128_cxx): New caching procs.
+
 2018-04-27  Tom Tromey  <tom@tromey.com>
 
 	PR rust/22545:
diff --git a/gdb/testsuite/gdb.base/align.exp b/gdb/testsuite/gdb.base/align.exp
new file mode 100644
index 0000000000..dfe53728ff
--- /dev/null
+++ b/gdb/testsuite/gdb.base/align.exp
@@ -0,0 +1,109 @@
+# Copyright 2018 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/>.
+
+# This file is part of the gdb testsuite
+
+# This tests that C11 _Alignof works in gdb, and that it agrees with
+# the compiler.
+
+# The types we're going to test.
+
+set typelist {
+    char {unsigned char}
+    short {unsigned short}
+    int {unsigned int}
+    long {unsigned long}
+    {long long} {unsigned long long}
+    float
+    double {long double}
+}
+
+if {[has_int128_c]} {
+    # Note we don't check "unsigned __int128" yet because at least gcc
+    # canonicalizes the name to "__int128 unsigned", and there isn't a
+    # c-exp.y production for this.
+    # https://sourceware.org/bugzilla/show_bug.cgi?id=20991
+    lappend typelist __int128
+}
+
+# Create the test file.
+
+set filename [standard_output_file align.c]
+set outfile [open $filename w]
+
+# Prologue.
+puts -nonewline $outfile "#define DEF(T,U) struct align_pair_ ## T ## _x_ ## U "
+puts $outfile "{ T one; U two; }"
+puts $outfile "unsigned a_void = _Alignof(void);"
+
+# First emit single items.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    if {$type != $utype} {
+	puts $outfile "typedef $type $utype;"
+    }
+    puts $outfile "$type item_$utype;"
+    puts $outfile "unsigned a_$utype\n  = _Alignof ($type);"
+    set utype [join [split $type] _]
+}
+
+# Now emit all pairs.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	puts $outfile "DEF ($utype, $uinner);"
+	set joined "${utype}_x_${uinner}"
+	puts $outfile "struct align_pair_$joined item_${joined};"
+	puts $outfile "unsigned a_${joined}"
+	puts $outfile "  = _Alignof (struct align_pair_${joined});"
+    }
+}
+
+# Epilogue.
+puts $outfile {
+    int main() {
+	return 0;
+    }
+}
+
+close $outfile
+
+standard_testfile $filename
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    perror "test suppressed"
+    return
+}
+
+foreach type $typelist {
+    set utype [join [split $type] _]
+    set expected [get_integer_valueof a_$utype 0]
+    gdb_test "print _Alignof($type)" " = $expected"
+
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
+	gdb_test "print _Alignof(struct align_pair_${utype}_x_${uinner})" \
+	    " = $expected"
+    }
+}
+
+set expected [get_integer_valueof a_void 0]
+gdb_test "print _Alignof(void)" " = $expected"
diff --git a/gdb/testsuite/gdb.cp/align.exp b/gdb/testsuite/gdb.cp/align.exp
new file mode 100644
index 0000000000..7d5955e53b
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/align.exp
@@ -0,0 +1,174 @@
+# Copyright 2018 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/>.
+
+# This file is part of the gdb testsuite
+
+# This tests that C++ alignof works in gdb, and that it agrees with
+# the compiler.
+
+if {[skip_cplus_tests]} { continue }
+
+# The types we're going to test.
+
+set typelist {
+    char {unsigned char}
+    short {unsigned short}
+    int {unsigned int}
+    long {unsigned long}
+    {long long} {unsigned long long}
+    float
+    double {long double}
+    empty
+    bigenum
+    vstruct
+    bfstruct
+    arrstruct
+    derived
+    derived2
+}
+
+if {[has_int128_cxx]} {
+    # Note we don't check "unsigned __int128" yet because at least gcc
+    # canonicalizes the name to "__int128 unsigned", and there isn't a
+    # c-exp.y production for this.
+    # https://sourceware.org/bugzilla/show_bug.cgi?id=20991
+    lappend typelist __int128
+}
+
+# Create the test file.
+
+set filename [standard_output_file align.cc]
+set outfile [open $filename w]
+
+# Prologue.
+puts $outfile {
+    template<typename T, typename U>
+    struct align_pair
+    {
+	T one;
+	U two;
+    };
+
+    template<typename T, typename U>
+    struct align_union
+    {
+	T one;
+	U two;
+    };
+
+    enum bigenum { VALUE = 0xffffffffull };
+
+    struct empty { };
+
+    struct vstruct { virtual ~vstruct() {}  char c; };
+
+    struct bfstruct { unsigned b : 3; };
+
+    struct arrstruct { short fld[7]; };
+
+    unsigned a_int3 = alignof (int[3]);
+
+    unsigned a_void = alignof (void);
+
+    struct base { char c; };
+    struct derived : public virtual base { int i; };
+
+    struct b2 : public virtual base { char d; };
+    struct derived2 : public b2, derived { char e; };
+}
+
+# First emit single items.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    puts $outfile "$type item_$utype;"
+    puts $outfile "unsigned a_$utype\n  = alignof ($type);"
+    puts $outfile "typedef $type t_$utype;"
+    puts $outfile "t_$utype item_t_$utype;"
+}
+
+# Now emit all pairs.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	puts $outfile "align_pair<$type, $inner> item_${utype}_x_${uinner};"
+	puts $outfile "unsigned a_${utype}_x_${uinner}"
+	puts $outfile "  = alignof (align_pair<$type, $inner>);"
+
+	puts $outfile "align_union<$type, $inner> item_${utype}_u_${uinner};"
+	puts $outfile "unsigned a_${utype}_u_${uinner}"
+	puts $outfile "  = alignof (align_union<$type, $inner>);"
+    }
+}
+
+# Epilogue.
+puts $outfile {
+    int main() {
+	return 0;
+    }
+}
+
+close $outfile
+
+standard_testfile $filename
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
+	 {debug nowarnings c++ additional_flags=-std=c++11}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    perror "test suppressed"
+    return
+}
+
+proc maybe_xfail {type} {
+    # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
+    # The g++ implementation of alignof is changing to match C11.
+    if {[is_x86_like_target]
+	&& [test_compiler_info {gcc-[0-8]-*}]
+	&& ($type == "double" || $type == "long long"
+	    || $type == "unsigned long long")} {
+	setup_xfail *-*-*
+    }
+}
+
+foreach type $typelist {
+    set utype [join [split $type] _]
+    set expected [get_integer_valueof a_$utype 0]
+
+    maybe_xfail $type
+    gdb_test "print alignof($type)" " = $expected"
+
+    maybe_xfail $type
+    gdb_test "print alignof(t_$utype)" " = $expected"
+
+    maybe_xfail $type
+    gdb_test "print alignof(typeof(item_$utype))" " = $expected"
+
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
+	gdb_test "print alignof(align_pair<${type},${inner}>)" " = $expected"
+
+	set expected [get_integer_valueof a_${utype}_u_${uinner} 0]
+	gdb_test "print alignof(align_union<${type},${inner}>)" " = $expected"
+    }
+}
+
+set expected [get_integer_valueof a_int3 0]
+gdb_test "print alignof(int\[3\])" " = $expected"
+set expected [get_integer_valueof a_void 0]
+gdb_test "print alignof(void)" " = $expected"
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-align.exp b/gdb/testsuite/gdb.dwarf2/dw2-align.exp
new file mode 100644
index 0000000000..2c2faf7591
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-align.exp
@@ -0,0 +1,83 @@
+# Copyright 2018 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/>.
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile main.c align-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcdir subdir srcfile
+
+    cu {} {
+	DW_TAG_compile_unit {
+                {DW_AT_language @DW_LANG_C_plus_plus}
+                {DW_AT_name     dw2-align.c}
+                {DW_AT_comp_dir /tmp}
+        } {
+	    declare_labels itype ptype
+
+            itype: DW_TAG_base_type {
+                {DW_AT_byte_size 4 DW_FORM_sdata}
+                {DW_AT_encoding  @DW_ATE_signed}
+                {DW_AT_name int_4096}
+		{DW_AT_alignment 4096 DW_FORM_sdata}
+            }
+
+            ptype: DW_TAG_pointer_type {
+                {DW_AT_byte_size 8 DW_FORM_sdata}
+                {DW_AT_type :$itype}
+		{DW_AT_alignment 4096 DW_FORM_sdata}
+            }
+
+            DW_TAG_typedef {
+                {DW_AT_name ptr_4096}
+                {DW_AT_type :$ptype}
+            }
+
+	    DW_TAG_structure_type {
+		{DW_AT_name "struct_4096"}
+		{DW_AT_byte_size 4096 DW_FORM_sdata}
+		{DW_AT_alignment 4096 DW_FORM_udata}
+	    } {
+		member {
+		    {name a}
+		    {type :$itype}
+		    {data_member_location 0 data1}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set lang c++"
+gdb_test "print alignof(int_4096)" " = 4096"
+gdb_test "print alignof(ptr_4096)" " = 4096"
+gdb_test "print alignof(struct_4096)" " = 4096"
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 4d48f5e3ad..0f05d043f2 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -3003,6 +3003,36 @@ gdb_caching_proc skip_btrace_pt_tests {
     return $skip_btrace_tests
 }
 
+# A helper that compiles a test case to see if __int128 is supported.
+proc gdb_int128_helper {lang} {
+    set src [standard_temp_file i128[pid].c]
+    set obj [standard_temp_file i128[pid].o]
+
+    verbose -log "checking $lang for __int128"
+    gdb_produce_source $src {
+	__int128 x;
+	int main() { return 0; }
+    }
+
+    set lines [gdb_compile $src $obj object [list nowarnings quiet $lang]]
+    file delete $src
+    file delete $obj
+
+    set result [expr {!![string match "" $lines]}]
+    verbose -log "__int128 for $lang result = $result"
+    return $result
+}
+
+# Return true if the C compiler understands the __int128 type.
+gdb_caching_proc has_int128_c {
+    return [gdb_int128_helper c]
+}
+
+# Return true if the C++ compiler understands the __int128 type.
+gdb_caching_proc has_int128_cxx {
+    return [gdb_int128_helper c++]
+}
+
 # Return whether we should skip tests for showing inlined functions in
 # backtraces.  Requires get_compiler_info and get_debug_format.
Pedro Alves April 30, 2018, 5:17 p.m. | #6
On 04/30/2018 05:49 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:

> 

> Pedro> This looks good to me.  A few comments on additional tests below,

> Pedro> but there's no need for another round of review for those.

> 

> This patch will need another review since I added some new stuff.


Looks good, thanks.

Thanks,
Pedro Alves

Patch

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1b5abb2f0d..73eba465a1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,16 @@ 
+2018-04-27  Tom Tromey  <tom@tromey.com>
+
+	PR exp/17095:
+	* NEWS: Update.
+	* std-operator.def (UNOP_ALIGNOF): New operator.
+	* expprint.c (dump_subexp_body_standard) <case UNOP_ALIGNOF>:
+	New.
+	* eval.c (evaluate_subexp_standard) <case UNOP_ALIGNOF>: New.
+	* c-lang.c (c_op_print_tab): Add alignof.
+	* c-exp.y (ALIGNOF): New token.
+	(exp): Add "ALIGNOF" production.
+	(ident_tokens): Add _Alignof and alignof.
+
 2018-04-27  Tom Tromey  <tom@tromey.com>
 
 	* i386-tdep.c (i386_type_align): New function.
diff --git a/gdb/NEWS b/gdb/NEWS
index 63fe30d175..6631b53475 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -9,6 +9,9 @@ 
 * 'info proc' now works on running processes on FreeBSD systems and core
   files created on FreeBSD systems.
 
+* C expressions can now use _Alignof, and C++ expressions can now use
+  alignof.
+
 * New commands
 
 set debug fbsd-nat
diff --git a/gdb/c-exp.y b/gdb/c-exp.y
index 9e2f80889f..3cee544106 100644
--- a/gdb/c-exp.y
+++ b/gdb/c-exp.y
@@ -173,7 +173,7 @@  static void c_print_token (FILE *file, int type, YYSTYPE value);
 %token <ssym> NAME_OR_INT
 
 %token OPERATOR
-%token STRUCT CLASS UNION ENUM SIZEOF UNSIGNED COLONCOLON
+%token STRUCT CLASS UNION ENUM SIZEOF ALIGNOF UNSIGNED COLONCOLON
 %token TEMPLATE
 %token ERROR
 %token NEW DELETE
@@ -307,6 +307,10 @@  exp	:	SIZEOF exp       %prec UNARY
 			{ write_exp_elt_opcode (pstate, UNOP_SIZEOF); }
 	;
 
+exp	:	ALIGNOF '(' type_exp ')'	%prec UNARY
+			{ write_exp_elt_opcode (pstate, UNOP_ALIGNOF); }
+	;
+
 exp	:	exp ARROW name
 			{ write_exp_elt_opcode (pstate, STRUCTOP_PTR);
 			  write_exp_string (pstate, $3);
@@ -2329,6 +2333,8 @@  static const struct token ident_tokens[] =
     {"struct", STRUCT, OP_NULL, 0},
     {"signed", SIGNED_KEYWORD, OP_NULL, 0},
     {"sizeof", SIZEOF, OP_NULL, 0},
+    {"_Alignof", ALIGNOF, OP_NULL, 0},
+    {"alignof", ALIGNOF, OP_NULL, FLAG_CXX},
     {"double", DOUBLE_KEYWORD, OP_NULL, 0},
     {"false", FALSEKEYWORD, OP_NULL, FLAG_CXX},
     {"class", CLASS, OP_NULL, FLAG_CXX},
diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index 658c7f7826..15e633f8c8 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -751,6 +751,7 @@  const struct op_print c_op_print_tab[] =
   {"*", UNOP_IND, PREC_PREFIX, 0},
   {"&", UNOP_ADDR, PREC_PREFIX, 0},
   {"sizeof ", UNOP_SIZEOF, PREC_PREFIX, 0},
+  {"alignof ", UNOP_ALIGNOF, PREC_PREFIX, 0},
   {"++", UNOP_PREINCREMENT, PREC_PREFIX, 0},
   {"--", UNOP_PREDECREMENT, PREC_PREFIX, 0},
   {NULL, OP_NULL, PREC_PREFIX, 0}
diff --git a/gdb/eval.c b/gdb/eval.c
index ad66f7c32c..2fdfdf9353 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -2667,6 +2667,19 @@  evaluate_subexp_standard (struct type *expect_type,
 	}
       return evaluate_subexp_for_sizeof (exp, pos, noside);
 
+    case UNOP_ALIGNOF:
+      {
+	struct type *type
+	  = value_type (evaluate_subexp (NULL_TYPE, exp, pos,
+					 EVAL_AVOID_SIDE_EFFECTS));
+	/* FIXME: This should be size_t.  */
+	struct type *size_type = builtin_type (exp->gdbarch)->builtin_int;
+	ULONGEST align = type_align (type);
+	if (align == 0)
+	  error (_("could not determine alignment of type"));
+	return value_from_longest (size_type, align);
+      }
+
     case UNOP_CAST:
       (*pos) += 2;
       type = exp->elts[pc + 1].type;
diff --git a/gdb/expprint.c b/gdb/expprint.c
index c906904599..5985f70a8f 100644
--- a/gdb/expprint.c
+++ b/gdb/expprint.c
@@ -846,6 +846,7 @@  dump_subexp_body_standard (struct expression *exp,
     case UNOP_PREDECREMENT:
     case UNOP_POSTDECREMENT:
     case UNOP_SIZEOF:
+    case UNOP_ALIGNOF:
     case UNOP_PLUS:
     case UNOP_CAP:
     case UNOP_CHR:
diff --git a/gdb/std-operator.def b/gdb/std-operator.def
index 87bb518877..1297c1edeb 100644
--- a/gdb/std-operator.def
+++ b/gdb/std-operator.def
@@ -234,6 +234,7 @@  OP (UNOP_POSTINCREMENT)		/* ++ after an expression */
 OP (UNOP_PREDECREMENT)		/* -- before an expression */
 OP (UNOP_POSTDECREMENT)		/* -- after an expression */
 OP (UNOP_SIZEOF)		/* Unary sizeof (followed by expression) */
+OP (UNOP_ALIGNOF)		/* Unary alignof (followed by expression) */
 
 OP (UNOP_PLUS)			/* Unary plus */
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 34da102c62..6909e8e0b1 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,10 @@ 
+2018-04-27  Tom Tromey  <tom@tromey.com>
+
+	PR exp/17095:
+	* gdb.dwarf2/dw2-align.exp: New file.
+	* gdb.cp/align.exp: New file.
+	* gdb.base/align.exp: New file.
+
 2018-04-26  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/gnu-ifunc.exp (set-break): Test that GDB resolves
diff --git a/gdb/testsuite/gdb.base/align.exp b/gdb/testsuite/gdb.base/align.exp
new file mode 100644
index 0000000000..6c13e24106
--- /dev/null
+++ b/gdb/testsuite/gdb.base/align.exp
@@ -0,0 +1,101 @@ 
+# Copyright 2018 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/>.
+
+# This file is part of the gdb testsuite
+
+# This tests that C11 _Alignof works in gdb, and that it agrees with
+# the compiler.
+
+# The types we're going to test.
+
+set typelist {
+    char {unsigned char}
+    short {unsigned short}
+    int {unsigned int}
+    long {unsigned long}
+    {long long} {unsigned long long}
+    float
+    double {long double}
+}
+
+# Create the test file.
+
+set filename [standard_output_file align.c]
+set outfile [open $filename w]
+
+# Prologue.
+puts -nonewline $outfile "#define DEF(T,U) struct align_pair_ ## T ## _x_ ## U "
+puts $outfile "{ T one; U two; }"
+puts $outfile "unsigned a_void = _Alignof(void);"
+
+# First emit single items.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    if {$type != $utype} {
+	puts $outfile "typedef $type $utype;"
+    }
+    puts $outfile "$type item_$utype;"
+    puts $outfile "unsigned a_$utype\n  = _Alignof ($type);"
+    set utype [join [split $type] _]
+}
+
+# Now emit all pairs.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	puts $outfile "DEF ($utype, $uinner);"
+	set joined "${utype}_x_${uinner}"
+	puts $outfile "struct align_pair_$joined item_${joined};"
+	puts $outfile "unsigned a_${joined}"
+	puts $outfile "  = _Alignof (struct align_pair_${joined});"
+    }
+}
+
+# Epilogue.
+puts $outfile {
+    int main() {
+	return 0;
+    }
+}
+
+close $outfile
+
+standard_testfile $filename
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    perror "test suppressed"
+    return
+}
+
+foreach type $typelist {
+    set utype [join [split $type] _]
+    set expected [get_integer_valueof a_$utype 0]
+    gdb_test "print _Alignof($type)" " = $expected"
+
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
+	gdb_test "print _Alignof(struct align_pair_${utype}_x_${uinner})" \
+	    " = $expected"
+    }
+}
+
+set expected [get_integer_valueof a_void 0]
+gdb_test "print _Alignof(void)" " = $expected"
diff --git a/gdb/testsuite/gdb.cp/align.exp b/gdb/testsuite/gdb.cp/align.exp
new file mode 100644
index 0000000000..fb5fb46a07
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/align.exp
@@ -0,0 +1,145 @@ 
+# Copyright 2018 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/>.
+
+# This file is part of the gdb testsuite
+
+# This tests that C++ alignof works in gdb, and that it agrees with
+# the compiler.
+
+if {[skip_cplus_tests]} { continue }
+
+# The types we're going to test.
+
+set typelist {
+    char {unsigned char}
+    short {unsigned short}
+    int {unsigned int}
+    long {unsigned long}
+    {long long} {unsigned long long}
+    float
+    double {long double}
+    empty
+    bigenum
+    vstruct
+    bfstruct
+    arrstruct
+}
+
+# Create the test file.
+
+set filename [standard_output_file align.cc]
+set outfile [open $filename w]
+
+# Prologue.
+puts $outfile {
+    template<typename T, typename U>
+    struct align_pair
+    {
+	T one;
+	U two;
+    };
+
+    template<typename T, typename U>
+    struct align_union
+    {
+	T one;
+	U two;
+    };
+
+    enum bigenum { VALUE = 0xffffffffull };
+
+    struct empty { };
+
+    struct vstruct { virtual ~vstruct() {}  char c; };
+
+    struct bfstruct { unsigned b : 3; };
+
+    struct arrstruct { short fld[7]; };
+}
+
+# First emit single items.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    puts $outfile "$type item_$utype;"
+    puts $outfile "unsigned a_$utype\n  = alignof ($type);"
+    puts $outfile "typedef $type t_$utype;"
+    puts $outfile "t_$utype item_t_$utype;"
+}
+
+# Now emit all pairs.
+foreach type $typelist {
+    set utype [join [split $type] _]
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	puts $outfile "align_pair<$type, $inner> item_${utype}_x_${uinner};"
+	puts $outfile "unsigned a_${utype}_x_${uinner}"
+	puts $outfile "  = alignof (align_pair<$type, $inner>);"
+
+	puts $outfile "align_union<$type, $inner> item_${utype}_u_${uinner};"
+	puts $outfile "unsigned a_${utype}_u_${uinner}"
+	puts $outfile "  = alignof (align_union<$type, $inner>);"
+    }
+}
+
+# Epilogue.
+puts $outfile {
+    int main() {
+	return 0;
+    }
+}
+
+close $outfile
+
+standard_testfile $filename
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile \
+	 {debug c++ additional_flags=-std=c++11}]} {
+    return -1
+}
+
+if {![runto_main]} {
+    perror "test suppressed"
+    return
+}
+
+proc maybe_xfail {type} {
+    # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69560
+    # The g++ implementation of alignof is changing to match C11.
+    if {[is_x86_like_target]
+	&& ($type == "double" || $type == "long long"
+	    || $type == "unsigned long long")} {
+	setup_xfail *-*-*
+    }
+}
+
+foreach type $typelist {
+    set utype [join [split $type] _]
+    set expected [get_integer_valueof a_$utype 0]
+
+    maybe_xfail $type
+    gdb_test "print alignof($type)" " = $expected"
+
+    maybe_xfail $type
+    gdb_test "print alignof(t_$utype)" " = $expected"
+
+    foreach inner $typelist {
+	set uinner [join [split $inner] _]
+	set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
+	gdb_test "print alignof(align_pair<${type},${inner}>)" " = $expected"
+
+	set expected [get_integer_valueof a_${utype}_u_${uinner} 0]
+	gdb_test "print alignof(align_union<${type},${inner}>)" " = $expected"
+    }
+}
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-align.exp b/gdb/testsuite/gdb.dwarf2/dw2-align.exp
new file mode 100644
index 0000000000..2c2faf7591
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-align.exp
@@ -0,0 +1,83 @@ 
+# Copyright 2018 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/>.
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile main.c align-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcdir subdir srcfile
+
+    cu {} {
+	DW_TAG_compile_unit {
+                {DW_AT_language @DW_LANG_C_plus_plus}
+                {DW_AT_name     dw2-align.c}
+                {DW_AT_comp_dir /tmp}
+        } {
+	    declare_labels itype ptype
+
+            itype: DW_TAG_base_type {
+                {DW_AT_byte_size 4 DW_FORM_sdata}
+                {DW_AT_encoding  @DW_ATE_signed}
+                {DW_AT_name int_4096}
+		{DW_AT_alignment 4096 DW_FORM_sdata}
+            }
+
+            ptype: DW_TAG_pointer_type {
+                {DW_AT_byte_size 8 DW_FORM_sdata}
+                {DW_AT_type :$itype}
+		{DW_AT_alignment 4096 DW_FORM_sdata}
+            }
+
+            DW_TAG_typedef {
+                {DW_AT_name ptr_4096}
+                {DW_AT_type :$ptype}
+            }
+
+	    DW_TAG_structure_type {
+		{DW_AT_name "struct_4096"}
+		{DW_AT_byte_size 4096 DW_FORM_sdata}
+		{DW_AT_alignment 4096 DW_FORM_udata}
+	    } {
+		member {
+		    {name a}
+		    {type :$itype}
+		    {data_member_location 0 data1}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set lang c++"
+gdb_test "print alignof(int_4096)" " = 4096"
+gdb_test "print alignof(ptr_4096)" " = 4096"
+gdb_test "print alignof(struct_4096)" " = 4096"