调试时打印变量 - gdb 无法打印在另一个子例程中计算的变量

Question

我目前正在调试用 fortran 编写并用 gfortran 编译的代码。

我在使用 gdb 打印一些变量时遇到了问题。

例如，当我在子例程内部并且我想打印一个来自“外部”并且其大小取决于另一个子例程中计算的参数的变量时，看起来 gdb 无法识别矩阵的大小并且无法打印。

我在下面给出了一个简化的示例，以便清楚地显示：

subroutine stiff(id)  
implicit real*8 (a-h,o-z)  
common /a/nnp  
dimension id(5,nnp)  

这是 gdb 给出的一些结果

(gdb) print id  
$6 = ()  
(gdb) whatis id  
type = integer(kind=4) (5,0)  
(gdb) print nnp  
$7 = 15  

有没有办法解决这个问题，或者它是编程方式所固有的？这段代码是别人开发的，代码量很大，所以我可以改变所有声明变量的方式。
预先感谢您的任何帮助。

编辑：

请参阅下面的一个简单程序（我能想到的最简单的程序）。它与我正在处理的代码具有全局相同的结构，并且与我之前描述的 gdb 具有相同的行为。当进入输入子例程时，我无法打印“id”变量。

implicit real*8 (a-h,o-z)
dimension a(1000)
call markaz(a)
stop
end

subroutine markaz(a)

implicit real*8 (a-h,o-z)
dimension a(1000)    
common /a/nnn

call dim1(l1,l2)

call input(a(l1))

return
end

subroutine dim1(l1,l2)
implicit real*8 (a-h,o-z)
common /a/nnn     

print*, 'enter nnn:  ';read(*,*) nnn

l1=1
l2=l1+(nnn*5+1)/2

return
end

subroutine input(id)
implicit real*8 (a-h,o-z)
common /a/nnn     
dimension id(5,nnn)

do i=1,5
do j=1,nnn 
id(i,j)=1.0
enddo
enddo

return
end

这是我使用 gfortran 4.4.5 和 gdb 7.0.1 得到的结果

$ gfortran -g -fbacktrace test.for  
$ gdb ./a.out  
GNU gdb (GDB) 7.0.1-debian  
Copyright (C) 2009 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-linux-gnu".  
For bug reporting instructions, please see:  
<http://www.gnu.org/software/gdb/bugs/>...  
Reading symbols from /test_print/a.out...done.  
(gdb) break test.for :36  
Breakpoint 1 at 0x400a7d: file test.for, line 36.  
(gdb) run  
Starting program: /test_print/a.out   
 enter nnn:    
2  

Breakpoint 1, input (id=...) at test.for:37  
37        do i=1,5  
Current language:  auto  
The current source language is "auto; currently fortran".  
(gdb) whatis id  
type = integer(kind=4) (5,0)  
(gdb) print id  
$1 = ()  
(gdb) print nnn  
$2 = 2  
(gdb)   

Answer 1

对我来说，你的代码与 gdb 配合得很好。使用 gfortran 4.5.5 和 gdb 7.2 进行测试。它不应该是这种编程风格的任何固有限制。

[testy]$ gfortran -g -fbacktrace common2.f90

[testy]$ gdb ./a.out
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-48.el6)
Copyright (C) 2010 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/>...
Reading symbols from /home/x/f/testy/a.out...done.
(gdb) break common2.f90:73
Breakpoint 1 at 0x400a2d: file common2.f90, line 73.
(gdb) run
Starting program: /home/x/f/testy/a.out 
 enter nnn:  
4

Breakpoint 1, input (id=...) at common2.f90:73
73      do i=1,5
(gdb) whatis id
type = integer(kind=4) (5,4)
(gdb) print id
$1 = (( 0, 0, 0, 0, 0) ( 0, 0, 0, 0, 0) ( 0, 0, 0, 0, 0) ( 0, 0, 0, 0, 0) )
(gdb) print nnn
$2 = 4
(gdb)