[Bug libgomp/80881] New: [7.1 Regression] null pointer access in libgomp.h

["daniel.f.starke at freenet dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80881

            Bug ID: 80881
           Summary: [7.1 Regression] null pointer access in libgomp.h
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgomp
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daniel.f.starke at freenet dot de
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

GCC 7.1.0 compiled OpenMP applications fail with invalid memory access to
address 0.

Used configuration:
    ../../src/gcc-7.1.0/configure --host=x86_64-w64-mingw32
--enable-languages=c,c++ --enable-seh-exceptions --enable-threads=posix
--enable-tls --disable-nls --disable-shared --enable-static
--enable-fully-dynamic-string --enable-lto --enable-plugins --enable-libgomp
--with-dwarf2 --disable-win32-registry --enable-version-specific-runtime-libs
--prefix=/mingw64-64 --with-sysroot=/mingw64-64 --target=x86_64-w64-mingw32
--enable-targets=all --enable-checking=release
--with-gmp=/usr/new-gcc/lib/gmp-5.0.5 --with-mpfr=/usr/new-gcc/lib/mpfr-2.4.2
--with-mpc=/usr/new-gcc/lib/mpc-0.9 --with-isl=/usr/new-gcc/lib/isl-0.18
--with-cloog=/usr/new-gcc/lib/cloog-0.18.4 --with-host-libstdcxx='-lstdc++
-lsupc++' --disable-cloog-version-check --enable-cloog-backend=isl
    Thread model: posix
    gcc version 7.1.0 (GCC)

Sample application:
    #include <stdlib.h>
    #include <stdio.h>

    #define N 1024

    int main() {
        int i;
        float var[N];
        volatile float PI = 3.1415927;

    #   pragma omp parallel for private(i)
        for (i = 0; i < N; i++) {
                var[i] = (1024.0f / PI) + 0.5f;
        }

        return EXIT_SUCCESS;
    }

Error message from Dr.Memory (32-bit variant):
    Error #1: UNADDRESSABLE ACCESS: reading 0x00000000-0x00000004 4 byte(s)
    # 0 GOMP_parallel              
[../../../../../src/gcc-7.1.0/libgomp/libgomp.h:677]
    # 1 main                        [h:\Temp\cpp017/test.c:11]
    Note: @0:00:00.642 in thread 6700
    Note: instruction: mov    %gs:0x00 -> %esi

Error message from Dr.Memory (64-bit variant):
    Error #1: UNADDRESSABLE ACCESS: reading
0x0000000000000000-0x0000000000000008 8 byte(s)
    # 0 GOMP_parallel              
[../../../../src/gcc-7.1.0/libgomp/libgomp.h:677]
    # 1 main                        [h:\Temp\cpp017/test.c:11]
    Note: @0:00:00.170 in thread 1320
    Note: instruction: mov    %fs:0x00 -> %rdi