关于声明和SAVE属性gotcha的Fortran赋值 [英] Fortran assignment on declaration and SAVE attribute gotcha
问题描述
integer :: var = 0
在fortran 95中，如果您在声明中指定了一个变量， code> 它相当于
integer，save :: var = 0
因此变量在例程执行后被保留在C语言中为 static ），并且在再次调用时不会重新初始化。这种（恕我直言）危险行为背后的理由/技术问题是什么？ 我不认为有一些理由在这样的行为背后。
但据我所知，斯蒂法诺，你使用了错误的术语。在您的代码中没有赋值语句仅使用初始化表达式（0）初始化变量（var）初始化。
integer :: var = 0！类型声明&初始化
integer :: var！类型声明
var = 0！分配
所以这似乎只是委员会的设计决定。如果我们有这样的表达式（在类型声明语句中使用等号），它是初始化而不是赋值。在程序（而不是程序）执行过程中，初始化只发生一次。
然而，这种决定可能有一些历史原因。看一下这个线程。
今天，这样的行为是危险的，因为许多其他广泛使用的语言遵循关于初始化/赋值的另一个约定。
In fortran 95, if you assign a variable at declaration
integer :: var = 0
it is equivalent to
integer, save :: var = 0
and the variable is therefore preserved after routine execution (is equivalent to static in C speak) and does not get reinitialized when called again. What is the rationale/technical issue behind such (IMHO dangerous) behavior ?
解决方案 I don't think that there is some rationale behind such behavior.
But as far as I know, Stefano, you used wrong terminology. In your code there is no assignment statement only variable (var) initialization using initialization expression (0).
integer :: var = 0 ! type declaration & initialization
integer :: var ! type declaration
var = 0 ! assignment
So it seems that it was just committee design decision. If we have such expression (with equality sign in type declaration statement) it is initialization not assignment. And initialization takes place only once during program (and not procedures) execution.
However there might be some historical reasons for such decision. Take a look at this thread.
Today such behavior is dangerous because many other widely used languages follows another conventions about initialization/assignment.
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