cray指针和数组的分段错误:我做错了什么？

Question

我的代码很复杂，但下面的MWE Fortran程序显示了该问题，并导致了英特尔Fortran 18.0.5中的分段错误。

     forrtl: severe (174): SIGSEGV, segmentation fault occurred

回溯显示在NN= malloc(nsize)上调用malloc()时出现问题

对于gfortran，它还会导致以下错误

    ./a.out: free(): invalid next size (fast): 0x0000000000603b40 ***

源码是：

      program test
  c         this program tests memory allocation

      read(*,*)k
      call  test_cray(k)
      end

      subroutine test_cray(k)
  #ifdef BIT64
      integer*8 NN, nsize
  #endif
      real x(*)
      real*8 prob(k,k, 128, 128)
      real*8 prob1(k,k, 128, 128)
      real*8 prob2(k,k, 128, 128)
      pointer(NN , x)
      nsize =   k*4*128*128
      nsize =20
      NN= malloc(nsize)
      do i =1, 20
      x(i)=0.1*(i-1)
      end do
      NN =loc(x)
      write(*,*) NN
      !write(*,*) "shape of x=", shape(x)
      call shape_cray(NN)
      write(*,*)"shape_cray returned"
      end
      subroutine shape_cray(NN )
      real y
        pointer(nx , y)

     do i =1, 20
        nx = NN + (i-1)*4
         write(*,*)nx,  y
     end do

      write(*,*) NN
      write(*,*) "shape of y=", shape(y)
      write(*,*) "y=", y
      end

请注意，程序中的空格必须针对降价进行调整。在没有分段错误的情况下，正确的方法是什么？

下面是输出：

    prompt> ifort -g -O0 -traceback -DBIT64 -mcmodel=large cray_test1.F
    prompt> ./a.out
      128
      forrtl: severe (174): SIGSEGV, segmentation fault occurred
      Image              PC                Routine            Line   Source 
      libifcoremt.so.5   00007F70F617F49C  for__signal_handl Unknown  Unknown
      libpthread-2.12.s  00000034A2C0F790      Unknown      Unknown  Unknown
      a.out              0000000000400C3B  test_cray_                 19  cray_test1.F
    a.out              000000000040097D  MAIN__          5  cray_test1.F
    a.out              00000000004008CE  Unknown               Unknown  Unknown
    libc-2.12.so       00000034A241ED5D  __libc_start_main     Unknown  Unknown
    a.out              00000000004007D9  Unknown               Unknown  Unknown

我使用了k=120。

Answer 1

正确的答案是“不要使用Cray指针，使用可分配的实体”。但考虑到有人可能正在使用和更新遗留代码。这修复了您的示例并使代码现代化。注意，我没有使用contains子程序，也没有提供接口语句。所以，你仍然有隐式的接口。

  program test
     implicit none
     integer k
     read(*,*) k
     if (k > 0) call test_cray(k)
  end

  subroutine test_cray(k)

     use iso_c_binding, only : c_intptr_t

     implicit none

     integer, intent(in) :: k

     integer(c_intptr_t) nn
     integer i, nsize
     real x(*)
     pointer(nn, x)

     nsize = k
     nn = malloc(nsize)
     x(1:nsize) = 0.1 * [(i - 1, i = 1, nsize)]
     nn = loc(x)
     write(*,*) nn

     call shape_cray(nn, nsize)

  end subroutine test_cray

  subroutine shape_cray(nn, nsize)

     use iso_c_binding, only : c_intptr_t

     implicit none

     integer(c_intptr_t), intent(in) :: nn
     integer, intent(in) :: nsize

     real y
     integer i
     pointer(nx, y)

     do i = 1, nsize
        nx = nn + (i - 1) * 4  ! Assumes REAL is 4 bytes.
        write(*,*) nx, y
     end do

     write(*,*) nn
     write(*,*) "shape of y = ", shape(y)
     write(*,*) "y = ", y
  end subroutine shape_cray

对于gfortran，这给出了

gfcx -o z -fcray-pointer a.f
./z
2
671645728
671645728   0.00000000    
671645732  0.100000001    
671645728
shape of y = 
y =   0.100000001