[Bug c++/49508] New: [4.7 Regression] Bogus "control reaches end of non-void function" warning

[Bug c++/49508] New: [4.7 Regression] Bogus "control reaches end of non-void function" warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

           Summary: [4.7 Regression] Bogus "control reaches end of
                    non-void function" warning
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: paolo.carlini@oracle.com


In mainline, I see this, apparently bogus, warning which is not emitted by 4.6
(or ICC for that matter). Testcase distilled from 20_util/forward/1_neg.cc in
the v3 testsuite, compile with -Wreturn-type:

template<class T>
  struct shared_ptr
  {
  };

template<class T, class A1, class A2>
  shared_ptr<T>
  factory(const A1&, const A2&)
  {
    return shared_ptr<T>(new T());
  }

struct A
{
  A(int&, int&);
};

void g()
{
  factory<A>(1, 2);
}

[Bug c++/49508] [4.7 Regression] Bogus "control reaches end of non-void function" warning

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

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> 2011-06-23 08:44:03 UTC ---
Started with http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=149750.
(and is definitely emitted by g++ 4.6 too).
I wonder if this warning shouldn't be disabled when any errors have been
emitted already.

[Bug c++/49508] Bogus "control reaches end of non-void function" warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.7 Regression] Bogus      |Bogus "control reaches end
                   |"control reaches end of     |of non-void function"
                   |non-void function" warning  |warning

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-06-23 09:01:47 UTC ---
Indeed, I did something wrong with the shell variables, sorry, I'm removing the
regression marker. Still rather annoying anyway.

[Bug c++/49508] Bogus "control reaches end of non-void function" warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

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

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

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 01:22:07 UTC ---
Same issue.

*** This bug has been marked as a duplicate of bug 48087 ***

[Bug c++/49508] Bogus "control reaches end of non-void function" warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2011-10-19
         Resolution|DUPLICATE                   |
     Ever Confirmed|0                           |1

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-19 17:28:22 UTC ---
Not a duplicate, probably.

[Bug c++/49508] Bogus "control reaches end of non-void function" warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-20 01:16:23 UTC ---
.. and I mus say, this specific issue is quite pervasive, I'm seeing it more
and more while triaging recent issues with warnings enabled, hmpf!

[Bug c++/49508] Bogus "control reaches end of non-void function" warning

[redi at gcc dot gnu.org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

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

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

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm seeing this frequently too, I was about to create a new PR as follows:

struct Y { };
struct X {
  X(short*);
};
X f() { int i; return &i; }


w.cc: In function ‘X f()’:
w.cc:5:24: error: could not convert ‘& i’ from ‘int*’ to ‘X’
 X f() { int i; return &i; }
                        ^
w.cc:5:27: warning: control reaches end of non-void function [-Wreturn-type]
 X f() { int i; return &i; }
                           ^

The warning is useless, because as soon as the error is fixed the warning will
go away, so it adds nothing but noise to the output.

And it's also confusing because there's a return statement *right* *there*! I
can see it and GCC even printed it out! :-) It only reaches the end because GCC
decides to ignore the return statement that fails in order to continue
compiling the rest of the function.

This doesn't happen in all cases where the return statement has an error, e.g.
if the example above does return i; instead of return &i; there's no warning.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64717

Gert-jan Los <gerrit.los at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gerrit.los at gmail dot com

--- Comment #1 from Gert-jan Los <gerrit.los at gmail dot com> ---
Created attachment 34615
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34615&action=edit
test case with virtual destructor

version: gcc version 5.0.0 20150128 (experimental) (GCC)
options: -O -fsanitize=vptr -Werror=uninitialized

PostScript_Back_End.C.i: In function ‘void fn1()’:
PostScript_Back_End.C.i:8:34: error: ‘<anonymous>’ is used uninitialized in
this function [-Werror=uninitialized]
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Subject: [Bug sanitizer/64717] -fsanitize=vptr leads to warning:=?UTF-8?Q? ‘?=<anonymous>=?UTF-8?Q?’ may be used uninitialized in this function ?=[-Wmaybe-uninitialized]
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64717

--- Comment #2 from Gert-jan Los <gerrit.los at gmail dot com> ---
Created attachment 34616
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34616&action=edit
test case with virtual base class

version: gcc version 5.0.0 20150128 (experimental) (GCC)
options: -O -fsanitize=vptr -Werror=uninitialized

gap_widths.C.i: In function ‘void fn1()’:
gap_widths.C.i:13:41: error: ‘<anonymous>’ is used uninitialized in this
function [-Werror=uninitialized]
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Subject: [Bug lto/64860] New: multiple definition of typeinfo in 5.0 (4.9.2 works)
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd860

            Bug ID: 64860
           Summary: multiple definition of typeinfo in 5.0 (4.9.2 works)
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sirl at gcc dot gnu.org

Created attachment 34617
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id4617&actioníit
Simple testcase. Use "make" to reproduce.

While trying to construct a testcase for a 4.8 to 4.9 change of LTO linking
behaviour, I stumbled over this (just re-tested with r220248):

g++-5 -flto -fuse-linker-plugin -O2 -Wall -Wextra -c file1.cpp
g++-5 -flto -fuse-linker-plugin -O2 -Wall -Wextra -c file2.cpp
gcc-5  -flto -fuse-linker-plugin -Wl,-r -nostdlib -o lib1.lib file1.o
gcc-5  -flto -fuse-linker-plugin -Wl,-r -nostdlib -o lib2.lib file2.o
g++-5 -flto -fuse-linker-plugin -O2 -o testexe lib1.lib lib2.lib
lib2.lib:(.rodata+0x0): multiple definition of `typeinfo name for CDialogBase'
lib1.lib:(.rodata+0x0): first defined here
collect2: error: ld returned 1 exit status

# g++-5 -v
Using built-in specs.
COLLECT_GCC=g++-5
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/5/lto-wrapper
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,fortran --with-gxx-include-dir=/usr/include/c++/5
--enable-ssp --disable-libssp --disable-libvtv --disable-plugin
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--disable-libgcj --with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--with-default-libstdcxx-abi=c++98 --enable-version-specific-runtime-libs
--enable-linker-build-id --enable-linux-futex --program-suffix=-5
--without-system-libunwind --enable-multilib --with-arch-32=i586
--with-tune=generic --build=x86_64-suse-linux --host=x86_64-suse-linux
Thread model: posix
gcc version 5.0.0 20150129 (experimental) (SUSE Linux)

gcc-4.8.3 and 4.9.2 compile and link the same code just fine.

[Bug c++/49508] [4.8/4.9/5 regression] Bogus "control reaches end of non-void function" warning

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |ASSIGNED
                 CC|                            |jason at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
            Summary|Bogus "control reaches end  |[4.8/4.9/5 regression]
                   |of non-void function"       |Bogus "control reaches end
                   |warning                     |of non-void function"
                   |                            |warning

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
4.4 didn't warn, so it seems reasonable to call it a regression.

[Bug c++/49508] [4.8/4.9/5 regression] Bogus "control reaches end of non-void function" warning

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Jan 29 16:10:08 2015
New Revision: 220252

URL: https://gcc.gnu.org/viewcvs?rev=220252&root=gcc&view=rev
Log:
    PR c++/49508
    * semantics.c (finish_return_stmt): Suppress -Wreturn-type on
    erroneous return statement.

Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/semantics.c
    trunk/gcc/testsuite/g++.old-deja/g++.jason/report.C

[Bug c++/49508] [4.8/4.9/5 regression] Bogus "control reaches end of non-void function" warning

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49508

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.0

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for GCC 5.