[Bug c/45784] New: gcc OpenMP - error: invalid controlling predicate

[Bug c/45784] New: gcc OpenMP - error: invalid controlling predicate

[geir at cray dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45784

           Summary: gcc OpenMP - error: invalid controlling predicate
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: geir@cray.com


The test is verifying that the parallel for loop construct may use
a variable of a pointer type in C.  

The OpenMP API Version 3.0 (May 2008) describes this usage on page
39 of the document.

Currently the GNU gcc compiler produces the following messages for
this test case:

ISU3417.c: In function 'vla_test':
ISU3417.c:23:25: error: invalid controlling predicate

The PGI, Intel, and Cray compilers compile this test case successfully.

$ cat ISU3417.c
//  derived from OpenMP test omp3c/c03_2_5_1_2c.c
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#define NT 4
#define INCREMENT 2
#define ARRAY_SIZE INCREMENT*NT

// VLAs are standard only in C99; might as well use a C99-specific data type
// (long long int) while we're testing C99-specific features
void vla_test(int num_threads) {
    long long int *ptr, vla[INCREMENT*num_threads];
    //long long int *ptr, vla[INCREMENT*40];
    int i;

    // variable-length array initialized to -1
    for (i = 0; i < sizeof(vla)/sizeof(vla[0]); i++) {
        vla[i] = -1;
    }

    #pragma omp parallel shared(vla)
    {
        #pragma omp for schedule(static, 1)
        for (ptr = vla; ptr < vla + sizeof(vla)/sizeof(vla[0]); 
             ptr = ptr + INCREMENT)
             *ptr = omp_get_thread_num();
    }

    for (i = 0; i < sizeof(vla)/sizeof(vla[0]); i++) {
        if (vla[i] != (i % INCREMENT == 0 ? (i/INCREMENT) % num_threads : -1))
{
            fprintf(stderr, "%s:%i: FAIL - vla[%i] == %lli != %i\n", 
                    __FILE__, __LINE__, i, vla[i], 
                   (i % INCREMENT == 0 ? (i/INCREMENT) % num_threads : -1));
            exit(1);
        }
    }
}

int main(void) {
    omp_set_dynamic(0);
    omp_set_num_threads(NT);

    vla_test(NT);

    return 0;
}
$ gcc -c -fopenmp -std=c99 ISU3417.c
ISU3417.c: In function 'vla_test':
ISU3417.c:24:25: error: invalid controlling predicate
$

Other compilers working:

$ pgcc -mp -c ISU3417.c
$ icc -c -openmp ISU3417.c
$ cc -c -omp -V ISU3417.c
/opt/cray/xt-asyncpe/4.4.9/bin/cc: INFO: Compiling for compute nodes running
CLE.
Cray C : Version 7.2.7 (u7267c72242i72182p72540a72002e60006z72540)
Cray C :               (x7205r72009w71001t7207)
Cray C : Fri Sep 24, 2010  14:34:26
$

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[Bug c/45784] gcc OpenMP - error: invalid controlling predicate

[geir at cray dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45784

--- Comment #2 from Geir Johansen <geir at cray dot com> ---
Fails in GCC 4.8.0:

$ gcc --version
gcc (GCC) 4.8.0 20130322 (Cray Inc.)
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc -c -fopenmp -std=c99 ISU3417.c
ISU3417.c: In function 'vla_test':
ISU3417.c:24:25: error: invalid controlling predicate
         for (ptr = vla; ptr < vla + sizeof(vla)/sizeof(vla[0]);
                         ^
$