浮点异常是在新的gfortran版本中发出信号 [英] Floating-point exceptions are signalling in new gfortran version

问题描述

我目前正在努力调试我老板在90年代写过的一些软件的子程序。似乎有一个浮点异常出现在特定子例程的do循环中：

I am currently working to debug a subroutine of some software that my boss has written back in the 90s. There seems to be a floating-point exception that occurs in a do loop of a particular subroutine:

16  irad=1,incmax
    rr1=rr2
    rr2=rr2+rdiv
      if(rr1.gt.rlimit) goto 16
      if(pts(irad).gt.0.0) then
         discrm=(rmsden(mt,irad)/pts(irad))
     1          -((average(mt,irad)**2)/(pts(irad)**2))
      else
         discrm=0.0
      endif
      if(discrm.ge.0.0) then
         rmsden(mt,irad)=sqrt(discrm)
      else
         rmsden(mt,irad)=0.0
      endif

      average(mt,irad)=average(mt,irad)/pts(irad)
      average(mt,irad)=(average(mt,irad)*100.0)/bigmost(mt)
      rmsden(mt,irad)=(rmsden(mt,irad)*100.0)/bigmost(mt)
      denbot(mt,irad)=(denbot(mt,irad)*100.0)/bigmost(mt)
      dentop(mt,irad)=(dentop(mt,irad)*100.0)/bigmost(mt)
      iradmax(mt)=irad


 17   if(iverbose0.ge.1) then
         ipts=pts(irad)
         iptszero=ptszero(irad)
         if(ipts.eq.0) then
            average(mt,irad)=0.0
            rmsden(mt,irad)=0.0
            denbot(mt,irad)=0.0
            dentop(mt,irad)=0.0
         endif
         write(6,99) rr1,rr2,ipts,iptszero,average(mt,irad),
     1               rmsden(mt,irad),denbot(mt,irad),dentop(mt,irad)
 99      format(1x,2f9.2,2i8,2f8.1,2f8.1)
      endif
 16   continue
      stop 'PIPPA'

If I put the stop 'PIPPA' statement before "16  continue", the there are no errors. However, if the stop statement goes after the "16  continue", I get: 
Note: The following floating-point exceptions are signalling: IEEE_INVALID_FLAG
STOP PIPPA

在升级GCC编译器/库之前，这并没有发生。我承认我通过谷歌搜索发现了很多资源，但我仍然无法调试。我也在编译时尝试了 - fpe-trap 标志，但是它们不输出任何东西。

This didn't happen before upgrading the GCC compilers/libraries. I admit that I have found a lot of resources through Googling, but I am still unable to debug this. I have also tried the --fpe-trap flags upon compilation, however they do not output anything.

为什么gfortran现在是否抱怨？

Why does gfortran now complain?

推荐答案

这里似乎有两个问题。让我们试着回答每一个。

There seems to be two questions here. Lets try to answer each one.

1。为什么新的GFortran版本打印这样的信息

由于Fortran 2008标准要求执行STOP和ERROR STOP语句输出当前信号的列表FP例外（如果系统支持这种情况），GFortran自GFortran 4.9版开始遵循此规定。请参阅 https://gcc.gnu.org/ml/fortran/2013- 06 / msg00072.html 。

Since the Fortran 2008 standard requires that execution of the STOP and ERROR STOP statements outputs a list of currently signaling FP exceptions (if such a thing is supported by the system), GFortran follows this as of GFortran version 4.9. See https://gcc.gnu.org/ml/fortran/2013-06/msg00072.html .

2。为什么我的代码触发这个异常，为什么它只发生在新的GFortran版本中

很可能，之前的例外信号也是如此，但因为它没有在STOP语句中打印，所以您不知道它。由于你所展示的例子不是独立的（我不能编译和测试它），我只能推荐你尝试通常的调试命令行选项，比如-fcheck = all，-ffpe-trap = invalid，零，溢出-g -Wall -Wextra -Werror -pedantic，检查运行你的程序在valgrind等。

Very likely, the exception was signalling before as well, but since it wasn't printed at the STOP statement you weren't aware of it. Since the example you have showed isn't self-contained (I can't compile and test it), I can only recommend you try the usual debugging command line options such as "-fcheck=all, -ffpe-trap=invalid,zero,overflow -g -Wall -Wextra -Werror -pedantic", check running your program under valgrind etc.

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