[Bug c++/49100] New: [OpenMP]: Compiler error when inline method defined within OpenMP loop

[Bug c++/49100] New: [OpenMP]: Compiler error when inline method defined within OpenMP loop

[bisqwit at iki dot fi]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

           Summary: [OpenMP]: Compiler error when inline method defined
                    within OpenMP loop
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bisqwit@iki.fi


This report is similar to PR49043, but unlike it, this does not involve C++0x.

This valid code fails to compile on GCC.
GCC spews an "invalid exit from OpenMP structured block" error message.

int main()
{
    #pragma omp parallel for
    for(int a=0; a<10; ++a)
    {
        struct x
        {
            void test() { return; };
        };
    }
}

If the explicit "return" statement is removed, it compiles.
It is also triggered by code such as this:

struct y
{
    static bool test(int c) { return c==5; }
};

if put inside the OpenMP loop construct, meaning it happens for static and
non-static methods as long as they include an explicit "return" statement.

The purpose of this error is to catch exits from an OpenMP construct (return,
break, goto). No such thing happens when a function is called or defined. The
error is not given when the struct is defined outside the loop (even if invoked
inside the loop). It is clearly a parser error.

It failed on all GCC versions that I tried that support OpenMP. These include
GCC 4.2.4, 4.3.5, 4.4.6, 4.5.3 and 4.6.1.

I have not tested whether the patch committed as a result of PR49043 also fixes
this bug.

[Bug c++/49100] [OpenMP]: Compiler error when inline method defined within OpenMP loop

[bisqwit at iki dot fi]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

--- Comment #1 from Joel Yliluoma <bisqwit at iki dot fi> 2011-05-21 11:31:46 UTC ---
It also does not happen with C's nested functions. This for instance compiles
and works just fine (to my surprise).

#include <stdio.h>
int main()
{
    int a;
    #pragma omp parallel for
    for(a=0; a<10; ++a)
    {
        int c() { return 65; }
        putchar( c() );
    }
    return 0;
}

I venture into another bug report here, but I wonder if this is a bug or
intentional behavior, that the code below outputs "YYYYYYYYYY", as though the
variable "a" within c() is bound to the a from the surrounding context rather
than the OpenMP loop's private copy of "a". If the OpenMP loop is removed, it
outputs "ABCDEFGHIJ" as expected.

#include <stdio.h>
int main()
{
    int a = 24;
    #pragma omp parallel for
    for(a=0; a<10; ++a)
    {
        int c() { return a+65; }
        putchar( c() );
    }
    return 0;
}

[Bug c++/49100] [OpenMP]: Compiler error when inline method defined within OpenMP loop

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-07-25 09:54:13 UTC ---
The first comment has been resolved by PR49043, at least I can't reproduce this
anymore with current trunk or 4.6.
The second is a user bug, OpenMP standard says that you shouldn't reference in
a parallel region the original copy of the variable and you do exactly that
through the nested function.

*** This bug has been marked as a duplicate of bug 49043 ***

[Bug c++/49100] [OpenMP]: Compiler error when inline method defined within OpenMP loop

[bisqwit at iki dot fi]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

--- Comment #3 from Joel Yliluoma <bisqwit at iki dot fi> 2011-07-25 10:01:08 UTC ---
While it's true that one should not reference the original variable within the
loop, question is, why does the inner function reference the original variable
rather than the inloop variable when there's no explicit reference to the
original variable. A reference is established, by name, within the loop, but
within the loop there should be no possible way to reference the outside-loop
variable because the inner-loop namespace shadows the outer one, and hence the
reference should bind into the inner-loop variable, thus conforming to OpenMP
specification.

[Bug c++/49100] [OpenMP]: Compiler error when inline method defined within OpenMP loop

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-07-25 10:10:04 UTC ---
You are outside of the scope of OpenMP standard and C99 language.  GNU nested
functions and OpenMP simply don't play nicely together if the containing
function has #pragma omp parallel or #pragma omp task.

[Bug c++/49100] [OpenMP]: Compiler error when inline method defined within OpenMP loop

[bisqwit at iki dot fi]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49100

--- Comment #5 from Joel Yliluoma <bisqwit at iki dot fi> 2011-07-25 10:24:20 UTC ---
Obviously :) All right, thanks.