执行以下代码时出现段错误:
program test
call sub ('dave')
end program test
subroutine sub (arr)
character (*) :: arr
character (20) :: upperc
arr = upperc (arr)
return
end subroutine sub
character (*) function upperc (str)
integer i, l
character (*) :: str
upperc = str
l = len (str)
do i = 1, l
icode = ichar (str (i:i))
if ((icode >= ichar ('a')).and.(icode <= ichar ('z'))) then
upperc (i:i) = char (ichar ('A') + icode - ichar('a'))
end if
enddo
return
end function upperc
seg 错误发生在以下行:
arr = upperc (arr)
这是编译和 GDB 运行时输出:
[dave@VM-15 ~]$ gfortran -g -Wall test.f90
[dave@VM-15 ~]$ gdb
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-80.el7
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
(gdb) file ./a.out
Reading symbols from /home/dave/a.out...done.
(gdb) run
Starting program: /home/dave/./a.out
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff70f1fa3 in __memmove_ssse3_back () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install glibc- 2.17-106.el7_2.8.x86_64 libgcc-4.8.5-4.el7.x86_64 libgfortran-4.8.5-4.el7.x86_64 libquadmath-4.8.5-4.el7.x86_64
(gdb) backtrace
#0 0x00007ffff70f1fa3 in __memmove_ssse3_back () from /lib64/libc.so.6
#1 0x000000000040078c in sub (arr='dave', _arr=4) at test.f90:13
#2 0x00000000004008e9 in test () at test.f90:3
#3 0x000000000040091f in main (argc=1, argv=0x7fffffffe7b3) at test.f90:5
#4 0x00007ffff6fc3b15 in __libc_start_main () from /lib64/libc.so.6
#5 0x0000000000400669 in _start ()
(gdb) q
A debugging session is active.
Inferior 1 [process 20941] will be killed.
[dave@VM-15 ~]$
我有一种有趣的感觉，这与我传递文字有关，但也许不是。
为了解决这个问题，我尝试了以下方法，效果很好:
program test2
character(20) text
text = 'dave'
call sub (text)
end program test2
subroutine sub (arr)
character (*) :: arr
character (20) :: upperc
arr = upperc (arr)
return
end subroutine sub
character (*) function upperc (str)
integer i, l
character (*) :: str
upperc = str
l = len (str)
do i = 1, l
icode = ichar (str (i:i))
if ((icode >= ichar ('a')).and.(icode <= ichar ('z'))) then
upperc (i:i) = char (ichar ('A') + icode - ichar('a'))
end if
enddo
return
end function upperc
谁能告诉我这是怎么回事？
最佳答案
问题是子例程sub从程序test2写入变量text。当您没有将变量作为 sub 的参数，而只是像第一个程序 test 中那样提供 'dave' 时，Fortran 会覆盖内存中未分配为变量的区域。这会导致段错误。
下面您可以看到您的工作示例。请注意两个更改:
字符
text的长度设置为6而不是20。这样做是为了证明它仍然可以组合在一起，因为子例程sub采用任意长度的参数。我们将变量
text的值写入控制台 2 倍，并通过call sub(text)更改它
program test3
character(6) text
text = 'dave'
write(*,*) text
call sub (text)
write(*,*) text
end program test3
subroutine sub (arr)
character (*) :: arr
character (20) :: upperc
arr = upperc (arr)
return
end subroutine sub
character (*) function upperc (str)
integer i, l
character (*) :: str
upperc = str
l = len (str)
do i = 1, l
icode = ichar (str (i:i))
if ((icode >= ichar ('a')).and.(icode <= ichar ('z'))) then
upperc (i:i) = char (ichar ('A') + icode - ichar('a'))
end if
enddo
return
end function upperc
关于segmentation-fault - 假定大小数组的段错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40473127/