[Bug build/31141] New: gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[Bug build/31141] New: gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[jremus at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

            Bug ID: 31141
           Summary: gdbsupport fails to compile with clang due to missing
                    C++ prototype for operator delete
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: jremus at linux dot ibm.com
  Target Milestone: ---

gdbsupport fails to compile with clang on s390x and x86 since commit
553b78748fd ("Rely on C++17 <new> in new-op.cc") as follows:

$ make
make  all-recursive
make[1]: Entering directory
'/home/jremus/my-dev-stuff/binutils-build/gdbsupport'
make[2]: Entering directory
'/home/jremus/my-dev-stuff/binutils-build/gdbsupport'
  CXX      new-op.o
../../binutils-gdb/gdbsupport/new-op.cc:114:1: error: no previous prototype for
function 'operator delete' [-Werror,-Wmissing-prototypes]
operator delete (void *p, std::size_t) noexcept
^
../../binutils-gdb/gdbsupport/new-op.cc:113:1: note: declare 'static' if the
function is not intended to be used outside of this translation unit
void
^
static
../../binutils-gdb/gdbsupport/new-op.cc:132:1: error: no previous prototype for
function 'operator delete[]' [-Werror,-Wmissing-prototypes]
operator delete[] (void *p, std::size_t) noexcept
^
../../binutils-gdb/gdbsupport/new-op.cc:131:1: note: declare 'static' if the
function is not intended to be used outside of this translation unit
void
^
static
2 errors generated.
make[2]: *** [Makefile:554: new-op.o] Error 1
make[2]: Leaving directory
'/home/jremus/my-dev-stuff/binutils-build/gdbsupport'
make[1]: *** [Makefile:574: all-recursive] Error 1
make[1]: Leaving directory
'/home/jremus/my-dev-stuff/binutils-build/gdbsupport'
make: *** [Makefile:446: all] Error 2


It works again when reverting commit 553b78748fd ("Rely on C++17 <new> in
new-op.cc").


My approach to build with clang are as follows:

cd $HOME
git clone git://sourceware.org/git/binutils-gdb.git
mkdir binutils-build
cd binutils-build
CC=clang CXX=clang++ ../binutils-gdb/configure
make


My above test build on x86 was on Fedora 38 with clang 16.0.6 and gcc C++
system header files from package libstdc++-devel 13.2.1.

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[jremus at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Jens Remus <jremus at linux dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-12-11
     Ever confirmed|0                           |1

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
Seems like a clang bug but we can revert the patch.

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
https://sourceware.org/pipermail/gdb-patches/2023-December/205021.html

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[jremus at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

--- Comment #3 from Jens Remus <jremus at linux dot ibm.com> ---
Thanks, Tom! Peeking at /usr/include/c++/13/new it looks like both subject
operator delete instances are guarded by __cpp_sized_deallocation:

#if __cpp_sized_deallocation
void operator delete(void*, std::size_t) _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
void operator delete[](void*, std::size_t) _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
#endif

Maybe that helps identify what would need to be changed in the build to make it
work with clang?

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[jremus at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Jens Remus <jremus at linux dot ibm.com> changed:

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

--- Comment #4 from Jens Remus <jremus at linux dot ibm.com> ---
Hello Tom, I can confirm that your referenced patch resolves the gdb build
issue with clang on both s390 and x86. Thanks!

Googling for "clang __cpp_sized_deallocation" I found that clang requires the
command-line option -fsized-deallocation to support C++ sized deallocation:
https://bcain-llvm.readthedocs.io/projects/clang/en/release_37/ReleaseNotes/#new-compiler-flags
https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fsized-deallocation

Further details:
https://reviews.llvm.org/D8467

Ongoing effort to enable C++ sized deallocation by default:
https://reviews.llvm.org/D112921

Besides reverting your changes there could possibly be two alternative
approaches:

1. Add -fsized-deallocation to the C++ flags (see
https://github.com/tomhughes/valgrind/blob/75a6b5764a264f2f2897adef40ecb4827b0bfa97/configure.ac#L2697)

2. Guard the two subject functions with __cpp_sized_deallocation in
gdbsupport/new-op.cc, provided they are currently unused.

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Tom Tromey <tromey at sourceware dot org> changed:

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

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
Reopening until the patch lands.

-fsized-deallocation sounds like more of a pain than just
reverting the patch, IMO.

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

--- Comment #6 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=9b9e5c09b1879766af959d276e99780982f4350b

commit 9b9e5c09b1879766af959d276e99780982f4350b
Author: Tom Tromey <tromey@adacore.com>
Date:   Mon Dec 11 10:04:23 2023 -0700

    Fix build with clang 16

    clang 16 reports a missing declaration in new-op.cc.  We believed
    these operators to be declared starting with C++14, but apparently
    that is not the case.

    This patch reverts the earlier change and then updates the comment to
    reflect the current state.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31141

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[Bug build/31141] gdbsupport fails to compile with clang due to missing C++ prototype for operator delete

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31141

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|REOPENED                    |RESOLVED
   Target Milestone|---                         |15.1

--- Comment #7 from Tom Tromey <tromey at sourceware dot org> ---
Fixed now.

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