[Bug libstdc++/65928] New: std::find_if compilation errors

[Bug libstdc++/65928] New: std::find_if compilation errors

[david.claessens at tomra dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

            Bug ID: 65928
           Summary: std::find_if compilation errors
           Product: gcc
           Version: 5.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.claessens at tomra dot com
  Target Milestone: ---

Created attachment 35421
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35421&action=edit
preprocessed file

COLLECT_GCC=g++-5
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
5.1.0-0ubuntu11~14.04.1' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-5 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=c++98 --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 5.1.0 (Ubuntu 5.1.0-0ubuntu11~14.04.1)


The code below compiles fine under 4.9.2 but gives errors under 5.1.0

compiler command: g++-5 -std=c++1y bug.cpp

adding -Wall -Wextra does not change the output for v5.1.0 but gives
unused-but-set-variable warnings on v4.9.2


#include <string>
#include <cctype>
#include <algorithm>

int main(int, char **)
{
    const std::string test_string("this is a test");

    auto first_space = std::find_if(
            std::begin(test_string),
            std::end(test_string),
            std::isblank);

    int (*myblank)(int) = &std::isblank;

    auto _space = std::find_if(
            std::begin(test_string),
            std::end(test_string),
            myblank);

    return 0;
}

The compiler output:
bug.cpp: In function ‘int main(int, char**)’:
bug.cpp:13:25: error: no matching function for call to
‘find_if(std::basic_string<char>::const_iterator,
std::basic_string<char>::const_iterator, <unresolved overloaded function
type>)’
             std::isblank);
                         ^
In file included from /usr/include/c++/5/algorithm:62:0,
                 from bug.cpp:4:
/usr/include/c++/5/bits/stl_algo.h:3806:5: note: candidate: template<class
_IIter, class _Predicate> _IIter std::find_if(_IIter, _IIter, _Predicate)
     find_if(_InputIterator __first, _InputIterator __last,
     ^
/usr/include/c++/5/bits/stl_algo.h:3806:5: note:   template argument
deduction/substitution failed:
bug.cpp:13:25: note:   couldn't deduce template parameter ‘_Predicate’
             std::isblank);
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From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ada/65476] Long_Float array does not byte-swap correctly with reverse Scalar_Storage_Order
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide476

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-04-29
            Summary|Long_Float array does not   |Long_Float array does not
                   |byte swap correctly when    |byte-swap correctly with
                   |set to Scalar_Storage_Order |reverse
                   |with High Order First       |Scalar_Storage_Order
     Ever confirmed|0                           |1

--- Comment #1 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Confirmed.

[Bug libstdc++/65928] std::find_if compilation errors

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
It seems normal to me. There are now several functions called isblank in
namespace std, and the compiler doesn't know which one to pick when you don't
give it a hint (like you do for myblank). A more explicit diagnostic would be
nice though.

[Bug libstdc++/65928] std::find_if compilation errors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

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

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

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Definitely not a libstdc++ bug, the code is simply not valid C++ because
std::isblank is an overloaded function.

[Bug libstdc++/65928] std::find_if compilation errors

[david.claessens at tomra dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

--- Comment #3 from david.claessens at tomra dot com ---
To be honest, I would have expected that since only <cctype> is included and
not <locale> where the other version of isblank is defined, there would be no
confusion.

[Bug libstdc++/65928] std::find_if compilation errors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's unspecified whether any of your headers includes <locale>, and in our
implementation <string> includes it.

[Bug libstdc++/65928] std::find_if compilation errors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
More precisely, <string> includes <bits/localefwd.h> which declares (but does
not define) the overload of std::isblank.

[Bug libstdc++/65928] std::find_if compilation errors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The code is invalid. No amount of fiddling about with headers will change that.
Even if you manage to find some combination that works today, it might not work
tomorrow or with a different compiler. Fix the code.