[Bug c++/66966] New: Missing diagnostic message for ill-formed program with anonymous enum

[Bug c++/66966] New: Missing diagnostic message for ill-formed program with anonymous enum

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

            Bug ID: 66966
           Summary: Missing diagnostic message for ill-formed program with
                    anonymous enum
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: anders.granlund.0 at gmail dot com
  Target Milestone: ---

Consider the following program (prog.cc):

  enum {};
  int main() {}

This is ill-formed according to [dcl.dcl]/5 of the c++ standard:

  http://eel.is/c++draft/dcl.dcl#5

Compile the program with the following command line:

  gcc prog.cc -std=c++98 -pedantic-errors -w

Observe that no diagnostic message is emitted. At least one diagnostic message
is expected since the program is ill-formed.

The bug 54216 that has been fixed seems to be similar. The difference is that
I'm using -w and -pedantic-errors. 

Could the bug be caused by a general problem of some errors getting hidden by
the combination -w and -pedantic-errors? I suspect this since I get the
following error message if I remove -w:

  error: ISO C++ forbids empty anonymous enum

Output for gcc -v (the problem seems to be quite independent of this however):

Using built-in specs.
COLLECT_GCC=/usr/local/gcc-head/bin/g++
COLLECT_LTO_WRAPPER=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/heads/gcc/gcc-source/configure
--prefix=/usr/local/gcc-head --enable-languages=c,c++ --enable-lto
--disable-multilib --without-ppl --without-cloog-ppl --enable-checking=release
--disable-nls
Thread model: posix
gcc version 6.0.0 20150721 (experimental) (GCC) 
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++98' '-v' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 /usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/cc1plus -quiet
-v -imultiarch x86_64-linux-gnu -D_GNU_SOURCE prog.cc -quiet -dumpbase prog.cc
-mtune=generic -march=x86-64 -auxbase prog -std=c++98 -version -o
/tmp/ccHJNWUA.s
GNU C++98 (GCC) version 6.0.0 20150721 (experimental)
(x86_64-unknown-linux-gnu)
        compiled by GNU C version 6.0.0 20150721 (experimental), GMP version
5.1.2, MPFR version 3.1.2, MPC version 1.0.1
warning: GMP header version 5.1.2 differs from library version 5.0.2.
warning: MPFR header version 3.1.2 differs from library version 3.1.0-p3.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0/x86_64-unknown-linux-gnu

/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../include/c++/6.0.0/backward
 /usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/include
 /usr/local/include
 /usr/local/gcc-head/include
 /usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++98 (GCC) version 6.0.0 20150721 (experimental)
(x86_64-unknown-linux-gnu)
        compiled by GNU C version 6.0.0 20150721 (experimental), GMP version
5.1.2, MPFR version 3.1.2, MPC version 1.0.1
warning: GMP header version 5.1.2 differs from library version 5.0.2.
warning: MPFR header version 3.1.2 differs from library version 3.1.0-p3.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 498fb50b10eacf300a28f79d04f435a8
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++98' '-v' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 as -v --64 -o /tmp/ccpk87pk.o /tmp/ccHJNWUA.s
GNU assembler version 2.22 (x86_64-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.22
COMPILER_PATH=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/
LIBRARY_PATH=/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib64/:/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-o' 'prog.exe' '-std=c++98' '-v' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'
 /usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/collect2
-plugin
/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/liblto_plugin.so
-plugin-opt=/usr/local/gcc-head/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
-plugin-opt=-fresolution=/tmp/cc7VqyW3.res -plugin-opt=-pass-through=-lgcc_s
-plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lc
-plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lgcc
--eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o
prog.exe /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o
/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/crtbegin.o
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../../../lib64
-L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
-L/usr/lib/../lib64
-L/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/../../.. -rpath
/usr/local/gcc-head/lib64 -lpthread /tmp/ccpk87pk.o -lstdc++ -lm -lgcc_s -lgcc
-lc -lgcc_s -lgcc
/usr/local/gcc-head/lib/gcc/x86_64-unknown-linux-gnu/6.0.0/crtend.o
/usr/lib/x86_64-linux-gnu/crtn.o

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-07-22
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Both Clang and EDG accept this with "warning: declaration does not declare
anything"

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

Jonathan Wakely <redi at gcc dot gnu.org> changed:

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

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oh wait ... if you use -w then you are suppressing diagnostics, so you can't
really complain that there are no diagnostics!

So this seems invalid to me.

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

--- Comment #3 from Anders Granlund <anders.granlund.0 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> Oh wait ... if you use -w then you are suppressing diagnostics, so you can't
> really complain that there are no diagnostics!
> 
> So this seems invalid to me.

Note that I'm having -pedantic-errors also.

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

--- Comment #4 from Anders Granlund <anders.granlund.0 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> Oh wait ... if you use -w then you are suppressing diagnostics, so you can't
> really complain that there are no diagnostics!
> 
> So this seems invalid to me.

In this case -w suppressed an error when combined with -pedantic-errors.
Shouldn't -w only suppress warnings?

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

Anders Granlund <anders.granlund.0 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |---

--- Comment #5 from Anders Granlund <anders.granlund.0 at gmail dot com> ---
I'm reopening this because of my latest comment.

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[manu at gcc dot gnu.org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 3707 bytes --]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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

--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Anders Granlund from comment #4)
> In this case -w suppressed an error when combined with -pedantic-errors.
> Shouldn't -w only suppress warnings?

This is not how it works. -pedantic-errors (and -Werror) converts warnings into
errors, but -w suppresses all warnings, even before they are converted into
errors.

One could argue that conversion to error should happen before warnings are
suppressed (in order to make combinations such as -w -Werror=X do something
useful), but this has been the behavior since forever, I doubt it can be
changed now (unless you do an amazing job at proving that almost no one is
relying on the current behavior and you take care of implementing the change).
>From gcc-bugs-return-493024-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Wed Jul 22 14:22:41 2015
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/66969] New: Internal compiler error, segmentation fault
Date: Wed, 22 Jul 2015 14:22:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf969

            Bug ID: 66969
           Summary: Internal compiler error, segmentation fault
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lgmsantos+gccbug at gmail dot com
  Target Milestone: ---

Created attachment 36034
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id6034&actioníit
Source code and system info

The program itself has a bug, in function f the expression "size(A(1,:))" at x
variable definition, line 11, should to be "size(B(1,:))" instead. But that
causes a segmentation fault on compiling.

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[anders.granlund.0 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

Anders Granlund <anders.granlund.0 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #7 from Anders Granlund <anders.granlund.0 at gmail dot com> ---
OK. Seems to work differently in Clang but I guess they don't have the same
problem with legacy.

[Bug c++/66966] Missing diagnostic message for ill-formed program with anonymous enum

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66966

--- Comment #8 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Anders Granlund from comment #7)
> OK. Seems to work differently in Clang but I guess they don't have the same
> problem with legacy.

Changing defaults in GCC to match Clang is possible (we added caret, colors,
changed the behavior of https://gcc.gnu.org/wiki/FAQ#wnowarning), but someone
who thinks this is important enough needs to make the effort of implementing
the change, arguing convincingly for it and handling any issues that may arise.

The change is likely to be just splitting diagnostic_report_warnings_p so that
the check for inhibit_warnings in diagnostic.c:diagnostic_report_diagnostic()
can be moved after diagnostic->kind is reclassified while keeping the check for
system-headers as early as possible, so that warnings from system-headers
converted into errors are still suppressed.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf731

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-07-22
                 CC|                            |ramana at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #3 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
Confirmed.