将 C 字符串和 fortran 字符串混合在一个文件中
我有一个关于在一个文件中混合 C 字符串和 fortran 字符串的问题。
假设我正在使用固定长度 9 的名称字符串，我定义了一个长度宏，就像
#define NAME_LEN 9
在 .c 文件中一样。
有一个现有的 fortran 函数，让我们将其命名为 fortran_function(char* name)
现在我必须在 ac 函数中调用这个 fortran 函数，我们的名称是
c_function(char name[]) {
fortran_function(name)
}
现在的问题是，我应该如何声明 c_function签名？
c_function(char name[])
c_function(char name[NAME_LEN +1])
或者
c_function(char name[NAME_LEN])
在什么情况下，我应该使用 9 作为名称长度或 10？
我的理解是，只要将一个包含 9 个字符的空终止字符串传递给 c_function，所有声明都是正确的。是这样吗？
还有其他问题应该放在这里吗？有潜在的错误吗？
I have one question with mixing C-string and fortran-string in one file.
Supposed I am playing with the name string with fixed length 9, I define a length Macro like
#define NAME_LEN 9
in a .c file.
There is an existing fortran-function, let's name it fortran_function(char* name)
Now I have to call this fortran function in a c function, let's name is
c_function(char name[]) {
fortran_function(name)
}
Now the problem is, how should I declare the c_function signature?
c_function(char name[])
c_function(char name[NAME_LEN +1])
or
c_function(char name[NAME_LEN])
Under what situations, I should use 9 as name length or 10?
My understanding is that, as long as you passed a null-terminated string with 9 characters to the c_function, all the declaration are correct. Is that right?
Any other concern should be put here? Any potential bugs?
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如果我没记错的话，这里还有一个问题。 Fortran 不使用以 null 结尾的字符串；相反，它用 0x20（空格）填充缓冲区的右端。因此，如果您可以访问 Fortran 源代码，我将修改函数签名以将传入字符串的长度作为参数。否则，您可能会使代码的 Fortran 端崩溃。
There's one more gotcha here, if I remember correctly. Fortran does not use null-terminated strings; instead, it pads the right end of the buffer with 0x20 (space). So, if you have access to the Fortran source, I would modify the function signature to take the length of the passed-in string as an argument. Otherwise, you will probably crash the Fortran side of the code.
Dave 是正确的，字符串的标准 Fortran 概念是固定长度，在右侧用空格填充。 （Fortran 现在也有可变长度字符串，但这些还不常见，并且与 C 互操作会非常棘手。）如果您希望固定长度，则在 Fortran 代码中使用相同的参数 NAME_LEN ，并具有相同的值。戴夫关于额外长度论证的建议可能更好。
另一个改进是在 Fortran 端使用 ISO C 绑定工具（根据注释进行更正！）
等。“绑定”名称是 C 可以调用 Fortran 例程的名称 - 它可以与 Fortran 名称不同。作为 iso_c_binding 的一部分，还提供了符号 C_NULL_CHAR，您可以在 Fortran 代码中使用它来提供 C 期望的终止空字符等。
Dave is correct, the standard Fortran concept for strings is fixed-length, padded with blanks on the right. (Fortran now also have variable length strings, but these are not yet common and would be very tricky to inter-operate with C.) If you want the lengths fixed, then have the same parameter NAME_LEN in your Fortran code, with the same value. Dave's suggestion of an additional length argument is probably better.
An additional refinement is to use the ISO C Binding facility on the Fortran side (corrected per the comment!)
etc. The "bind" name is the name by which C can call the Fortran routine -- it can be different from the Fortran name. Also provided as part of the iso_c_binding is the symbol C_NULL_CHAR which you can use in the Fortran code to provide the terminating null character that C expects, etc.
这些电话没有区别。 C 编译器会将它们全部视为 char*。您只需确保在 c 中使用它之前将其 null 终止即可。如果您仅在 fortran 端使用该字符串并且 c 函数只是保留它，那么您不需要执行任何操作。
There's no difference to those calls. The c compiler will treat them all as char*. You just have to make sure you null terminate it before you use it in c. If you're only using the string in the fortran side and the c functions are just holding on to it, then you don't need to do anything.