[Bug c++/111790] New: Unwarranted missing template keyword warning

[Bug c++/111790] New: Unwarranted missing template keyword warning

[t.bartels@tu-berlin.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111790

            Bug ID: 111790
           Summary: Unwarranted missing template keyword warning
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: t.bartels@tu-berlin.de
  Target Milestone: ---

Consider the following code:

template <typename T> //no warning if this is not a template
struct X
{
    T v;
};

template <typename T>
inline void f() {
    X<T> x; //no warning with e.g. X<int>
    if(x.v < 0 && 
       0 > -1) {} //No warning without the "-"
}

int main() {
    f<int>(); //Still get a warning without this instantiation.
}

GCC 12, 13, current trunk and seemingly everything after b8ffa71e427 give me a
warning for this:
warning: expected 'template' keyword before dependent template name
[-Wmissing-template-keyword]

But GCC compiles it, so it seems to interpret it correctly at some point after
triggering the warning. I tried to look into it and thought that maybe 

cp_lexer_peek_token (parser->lexer)->type
              <= CPP_LAST_PUNCTUATOR

in line 6447 of gcc/cp/parser.cc is too general but I do not have a proposed
patch.

[Bug c++/111790] Unwarranted missing template keyword warning

[t.bartels@tu-berlin.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111790

--- Comment #1 from Tinko Sebastian Bartels <t.bartels@tu-berlin.de> ---
A command line that can trigger the behavior is

g++ main.cpp

One of the versions for which it occurs is

g++ -v
Es werden eingebaute Spezifikationen verwendet.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/13.2.1/lto-wrapper
Ziel: x86_64-pc-linux-gnu
Konfiguriert mit: /build/gcc/src/gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,objc,obj-c++ --enable-bootstrap
--prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--with-build-config=bootstrap-lto --with-linker-hash-style=gnu
--with-system-zlib --enable-__cxa_atexit --enable-cet=auto
--enable-checking=release --enable-clocale=gnu --enable-default-pie
--enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object
--enable-libstdcxx-backtrace --enable-link-serialization=1
--enable-linker-build-id --enable-lto --enable-multilib --enable-plugin
--enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-werror
Thread-Modell: posix
Unterstützte LTO-Kompressionsalgorithmen: zlib zstd
gcc-Version 13.2.1 20230801 (GCC)

[Bug c++/111790] [12/13/14 Regression] Unwarranted missing template keyword warning

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111790

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.4
            Summary|Unwarranted missing         |[12/13/14 Regression]
                   |template keyword warning    |Unwarranted missing
                   |                            |template keyword warning
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-10-16
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Confirmed.

[Bug c++/111790] [12/13/14 Regression] Unwarranted missing template keyword warning

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111790

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r12-6563-gb8ffa71e4271ae:

commit b8ffa71e4271ae562c2d315b9b24c4979bbf8227
Author: Anthony Sharp <anthonysharp15@gmail.com>
Date:   Sat Dec 4 17:23:22 2021 +0000

    c++: warning for dependent template members [PR70417]


But is seems to me this is the case of a false positive
<https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmissing-template-keyword>
talks about.  Wrapping "x.v < 0" in () suppresses the warning.

[Bug c++/111790] [12/13/14 Regression] Unwarranted missing template keyword warning

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111790

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |law at gcc dot gnu.org
           Priority|P3                          |P2