[Bug c++/59867] New: Template string literal loses first symbol

[Bug c++/59867] New: Template string literal loses first symbol

[i-hate-registration at mailinator dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

            Bug ID: 59867
           Summary: Template string literal loses first symbol
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: i-hate-registration at mailinator dot com

Created attachment 31880
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31880&action=edit
Template string literal works somehow strange in this example

Hi everyone,

When using a template string literal overload (template <class T, T... xs>) ,
for "123"_s, I get xs = {'2', '3'} instead of xs = {'1', '2', '3'}.

There's as minimal example as I could make in the attachment. When it's
compiled in its current way, it shows the following error:

> g++ -std=c++1y example.cpp -o example
example.cpp: In instantiation of ‘constexpr meta_array<T, xs ...>
operator""_s() [with T = char; T ...xs = {'2', '3'}]’:
example.cpp:40:44:   required from here
example.cpp:34:2: error: static assertion failed: What's wrong with you?
  static_assert(sizeof...(xs) == 3, "What's wrong with you?");
  ^

When I replace equality with inequality in static_assert:

> g++ -std=c++1y example.cpp -o example
example.cpp: In instantiation of ‘constexpr meta_array<T, xs ...>
operator""_s() [with T = char; T ...xs = {'1', '2', '3'}]’:
example.cpp:40:44:   required from here
example.cpp:35:2: error: static assertion failed: What's wrong with you?
  static_assert(sizeof...(xs) != 3, "What's wrong with you?");
  ^

As ""_s is used only once in the code and, I believe, there's no implicit way
it's called recursively, it looks like there's some kind of bug.

P.S. Thank you for the great work!
>From gcc-bugs-return-440792-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jan 17 22:43:38 2014
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From: "ian at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug go/59866] gccgo gc work buffer is misaligned
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY866

--- Comment #2 from ian at gcc dot gnu.org <ian at gcc dot gnu.org> ---
Author: ian
Date: Fri Jan 17 22:43:03 2014
New Revision: 206738

URL: http://gcc.gnu.org/viewcvs?rev 6738&root=gcc&view=rev
Log:
    PR go/59866
runtime: Force work variable in mgc0 to be aligned on 8-byte boundary.

Modified:
    trunk/libgo/runtime/mgc0.c

[Bug c++/59867] Template string literal loses first symbol

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Comment on attachment 31880
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31880
Template string literal works somehow strange in this example

>#include <iostream>
>using namespace std;
>
>// constant
>template <class T, T x>
>struct meta_value {
>	typedef meta_value type;
>	typedef T value_type;
>	static const T value = x;
>};
>
>// array
>template <class T, T... data>
>struct meta_array {
>	typedef meta_array type;
>	typedef T item_type;
>};
>
>// static array -> runtime array conversion utility
>template <class T>
>struct array_gen;
>
>template <class T, T... xs>
>struct array_gen<meta_array<T, xs...>> {
>	static const T value[sizeof...(xs)];
>};
>
>template <class T, T... xs>
>const T array_gen<meta_array<T, xs...>>::value[sizeof...(xs)] = { xs... };
>
>// static string
>template <class T, T... xs>
>constexpr meta_array<T, xs...> operator "" _s() {
>	static_assert(sizeof...(xs) == 3, "What's wrong with you?");
>	//static_assert(sizeof...(xs) != 3, "What's wrong with you?");
>	return meta_array<T, xs...>();
>}
>
>int main() {
>	const char (& xs)[2] = array_gen<decltype("123"_s)>::value;
>	for (auto & x : xs) cout << x << endl;
>}
>From gcc-bugs-return-440806-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sat Jan 18 07:34:03 2014
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Subject: [Bug c++/59867] Template string literal loses first symbol
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY867

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This looks just as a missed diagnostics of invalid source.
Both in C++11 and in n3690 there is in [over.literal]/5:
"The declaration of a literal operator template shall have an empty
parameter-declaration-clause and its template-parameter-list shall have a
single template-parameter that is a non-type template parameter pack (14.5.3)
with element type char."

[Bug c++/59867] Template string literal loses first symbol

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-01-18
     Ever confirmed|0                           |1

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Looks like we have a C++1y extension of the C++11 requirements on the
parameters in place (see toward the end of
cp_parser_template_declaration_after_export) which however we don't handle
correctly. I think Ed should clarify the intention and either tighten the
diagnostic in C++1y mode too or make sure this kind of code is handled
correctly (well, ideally, in C++11 mode we shouldn't provide the static_assert
message, just emit the parsing error)

[Bug c++/59867] Template string literal loses first symbol

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
In fact current clang accepts the code as a GNU extension and we don't ;)

[Bug c++/59867] Template string literal loses first symbol

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |emsr at gcc dot gnu.org

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Ah, it looks like this is n3599
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3599.html added in
r198018.  Couldn't find what is this state (if it is going to be in C++14,
C++17 or when?).

[Bug c++/59867] Template string literal loses first symbol

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> ---
I went through the formal motions passed in Bristol and Chicago and didn't see
it, thus shouldn't be in C++14. C++17 maybe, nothing is decided yet.

[Bug c++/59867] Template string literal loses first symbol

[i-hate-registration at mailinator dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #7 from Username <i-hate-registration at mailinator dot com> ---
I've heard that it was previously expected to be in C++14, though it was
somehow forgotten, because the fix is quite small and one could currently do it
with a little bit of preprocessor/constexpr (MPLLIBS_STRING in
https://github.com/sabel83/mpllibs).

Nevertheless, compile-time strings are very useful (as it's shown in D), and
will be a part of standard sooner or later.

[Bug c++/59867] Template string literal loses first symbol

[3dw4rd at verizon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #10 from Ed Smith-Rowland <3dw4rd at verizon dot net> ---
Right now, -std=c++1y means anything after c++11.  Does anyone have an idea
about what happens when C++14 and these other TSen actually come out?

I guess I was thinking as far as this extension is concerned:
1) It is left *on* for c++1y and gnu++1y for backward compatibility. Sigh.
2) It is *on* with gnu++14 as an extension.
3) It is *off* with c++14 for strict ANSI compatibility.
4) It is maybe on for c++17 and gnu++17 when & if it ever gets in.

We seem to have dynamically sized array (VLA) in this category as well.

[Bug c++/59867] Template string literal loses first symbol

[3dw4rd at verizon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #11 from Ed Smith-Rowland <3dw4rd at verizon dot net> ---
This may be related to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58781 -
another decltype user-defined literal bug.

[Bug c++/59867] Template string literal loses first symbol

[3dw4rd at verizon dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #13 from Ed Smith-Rowland <3dw4rd at verizon dot net> ---
Created attachment 33020
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33020&action=edit
Patch 58781, 59867, 60249, ...

I think I got it.

Don't mess with the token stream.

PR C++/58781 - Unicode strings broken in a strange way
PR C++/59867 - Template string literal loses first symbol
PR C++/60249 - Compiler goes into semi-infinite loop with wrong usage of user
defined string literals
Plus I fixed an misleading error message for string literal operator templates
(not available in C++11).

[Bug c++/59867] Template string literal loses first symbol

[3dw4rd at verizon dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #12 from Ed Smith-Rowland <3dw4rd at verizon dot net> ---
Created attachment 33019
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33019&action=edit
Patch 58781, 59867, 60249, ...

I think I got it.

Don't mess with the token stream.

PR C++/58781 - Unicode strings broken in a strange way
PR C++/59867 - Template string literal loses first symbol
PR C++/60249 - Compiler goes into semi-infinite loop with wrong usage of user
defined string literals
Plus I fixed an misleading error message for string literal operator templates
(not available in C++11).

[Bug c++/59867] Template string literal loses first symbol

[emsr at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #14 from emsr at gcc dot gnu.org ---
Author: emsr
Date: Tue Jul  1 03:13:17 2014
New Revision: 212186

URL: https://gcc.gnu.org/viewcvs?rev=212186&root=gcc&view=rev
Log:
cp/

2014-06-28  Edward Smith-Rowland  <3dw4rd@verizon.net>

    PR c++/58781
    PR c++/60249
    PR c++/59867
    * parser.c (cp_parser_userdef_string_literal()): Take a tree
    not a cp_token*. (cp_parser_string_literal(): Don't hack
    the token stream!


testsuite/

2014-06-28  Edward Smith-Rowland  <3dw4rd@verizon.net>

    PR c++/58781
    PR c++/60249
    PR c++/59867
    * testsuite/g++.dg/cpp0x/pr58781.C: New.
    * testsuite/g++.dg/cpp0x/pr60249.C: New.
    * testsuite/g++.dg/cpp1y/pr59867.C: New.



Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/pr58781.C
    trunk/gcc/testsuite/g++.dg/cpp0x/pr60249.C
    trunk/gcc/testsuite/g++.dg/cpp1y/pr59867.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/parser.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/59867] Template string literal loses first symbol

[emsr at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

--- Comment #15 from emsr at gcc dot gnu.org ---
Author: emsr
Date: Tue Jul  1 05:30:34 2014
New Revision: 212188

URL: https://gcc.gnu.org/viewcvs?rev=212188&root=gcc&view=rev
Log:
cp/

2014-06-28  Edward Smith-Rowland  <3dw4rd@verizon.net>

    PR c++/58781
    PR c++/60249
    PR c++/59867
    * parser.c (cp_parser_userdef_string_literal()): Take a tree
    not a cp_token*. (cp_parser_string_literal(): Don't hack
    the token stream!

testsuite/

2014-06-28  Edward Smith-Rowland  <3dw4rd@verizon.net>

    PR c++/58781
    PR c++/60249
    PR c++/59867
    * testsuite/g++.dg/cpp0x/pr58781.C: New.
    * testsuite/g++.dg/cpp0x/pr60249.C: New.
    * testsuite/g++.dg/cpp1y/pr59867.C: New.


Added:
    branches/gcc-4_9-branch/gcc/testsuite/g++.dg/cpp0x/pr58781.C
    branches/gcc-4_9-branch/gcc/testsuite/g++.dg/cpp0x/pr60249.C
    branches/gcc-4_9-branch/gcc/testsuite/g++.dg/cpp1y/pr59867.C
Modified:
    branches/gcc-4_9-branch/gcc/cp/ChangeLog
    branches/gcc-4_9-branch/gcc/cp/parser.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog

[Bug c++/59867] Template string literal loses first symbol

[emsr at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59867

emsr at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #16 from emsr at gcc dot gnu.org ---
Fixed.