[Openmp-dev] warnings in omp.h from Clang

[Stephen Siegel via Openmp-dev]

Thanks, Andrey.   Your answer clued me in to a solution…

basie:tmp siegel$ clang-mp-9.0 -fopenmp -isystem /opt/local/include/libomp -pedantic exp.c
basie:tmp siegel$

System files included from an -isystem path don’t have warnings reported (in gcc or clang).
I guess gcc -fopenmp adds the -isystem for you, but clang doesn’t.   Probably would be a good idea to make that change to clang.

-Steve


> On Jun 25, 2020, at 2:32 PM, Churbanov, Andrey <Andrey.Churbanov at intel.com> wrote:
> 
> Hi Steve,
> 
> You observed expected problem, and I am not sure if it can be solved.  Probably clang could suppress the warnings somehow, though I am not a compiler expert.
> 
> The omp_sched_monotonic is the part of OpenMP standard, which does not correspond well with the ISO C here.
> 
> The omp_*_handle_t  were intentionally made enumerators with the intention to store pointers there. That's why UINTPRT_MAX used to emphasize the size of the enumerator.
> The argument was that the advantage of enumeration versus integer for compilation (allows stricter type checking) overweighs the disadvantage of its non-conformance with the ISO C. Especially given that "all" known compilers support an extension that allows enumerator to be as big as any integer type.
> 
> Interestingly gcc does not complain on omp_sched_monotonic by default, but starts complaining if you point to its own include file via -I option (tried gcc version 9.3).
> 
> Regards,
> Andrey
> 
> -----Original Message-----
> From: Openmp-dev <openmp-dev-bounces at lists.llvm.org> On Behalf Of Stephen Siegel via Openmp-dev
> Sent: Thursday, June 25, 2020 6:37 PM
> To: openmp-dev at lists.llvm.org
> Subject: [Openmp-dev] warnings in omp.h from Clang
> 
> Hello,
> I’ve installed Clang 9.0 on my Mac using MacPorts.  When I compile a C/OpenMP program with the flag -pedantic, I get 4 warnings, all of the same kind, in omp.h, e.g. "ISO C restricts enumerator values to range of 'int'  (2147483648 is too large)”.   An example is below.   Do other people get this, or am I doing something wrong?
> Thanks,
> Steve
> 
> 
> basie:diffusion1d siegel$ cat exp.c
> #include <omp.h>
> int main() {
> }
> 
> basie:diffusion1d siegel$ clang-mp-9.0 -fopenmp -pedantic exp.c In file included from exp.c:1:
> /opt/local/include/libomp/omp.h:53:9: warning: ISO C restricts enumerator values to range of 'int'
>      (2147483648 is too large) [-Wpedantic]
>        omp_sched_monotonic = 0x80000000
>        ^                     ~~~~~~~~~~
> /opt/local/include/libomp/omp.h:302:7: warning: ISO C restricts enumerator values to range of 'int'
>      (18446744073709551615 is too large) [-Wpedantic]
>      KMP_ALLOCATOR_MAX_HANDLE = UINTPTR_MAX
>      ^                          ~~~~~~~~~~~
> /opt/local/include/libomp/omp.h:315:7: warning: ISO C restricts enumerator values to range of 'int'
>      (18446744073709551615 is too large) [-Wpedantic]
>      KMP_MEMSPACE_MAX_HANDLE = UINTPTR_MAX
>      ^                         ~~~~~~~~~~~
> /opt/local/include/libomp/omp.h:343:39: warning: ISO C restricts enumerator values to range of 'int'
>      (18446744073709551615 is too large) [-Wpedantic]
>    typedef enum omp_event_handle_t { KMP_EVENT_MAX_HANDLE = UINTPTR_MAX } omp_event_handle_t;
>                                      ^                      ~~~~~~~~~~~
> 4 warnings generated.
> basie:diffusion1d siegel$ more /opt/local/include/libomp/omp.h
> /*
> * include/omp.h.var
> */
> 
> 
> //===----------------------------------------------------------------------===//
> //
> // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
> // See https://llvm.org/LICENSE.txt for license information.
> // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===//
> 
> 
> #ifndef __OMP_H
> #   define __OMP_H
> 
> #   include <stdlib.h>
> #   include <stdint.h>
> 
> #   define KMP_VERSION_MAJOR    5
> #   define KMP_VERSION_MINOR    0
> #   define KMP_VERSION_BUILD    20140926
> #   define KMP_BUILD_DATE       "No_Timestamp"
> 
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