Re: [FFmpeg-devel] [PATCH v2 1/2] avutil/wchar_filename, file_open: Support long file names on Windows

[nil-admirari@mailo.com]

>> Not possible for stat precisely because of function and struct sharing a
>> name.

> That's exactly what is said above and before :-)

My previous question was not answered, so I had to look up the answer myself.

> I'm actually wondering how does it even compile. All stat structs in code
> become struct win32_stat, and all calls to stat become calls to win32_stat,
> which in turn wraps _wstati64. But _wstati64 does not accept struct win32_stat*,
> it accepts struct _stati64*. Content of these structs is probably identical, but
> it should not matter: C is typed nominally, not structurally.

Turns out C actually has a concept of compatible types:
https://en.cppreference.com/w/c/language/type.

The problems is:
> they are both structure/union/enumeration types, and
> - (c99) if one is declared with a tag, the other must also be declared with the same tag.
> ...
> If two declarations refer to the same object or function and do not use compatible types,
> the behavior of the program is undefined.

Your structure does not have the same tag as the CRT's one.
Are you sure you want to rely on undefined behaviour?

I haven't compiled your code, but the following simple example:

struct A { int a, b, c; };
struct B { int a, b, c; };
void printA(struct A *a);

struct B b = { 1, 2, 3 };
printA(&b);

generates a

warning: passing argument 1 of ‘printA’ from incompatible pointer type [-Wincompatible-pointer-types]
    |     printA(&b);
    |            ^~
    |            |
    |            struct B *
note: expected ‘struct A *’ but argument is of type ‘struct B *’
    | void printA(struct A *a)

Are you sure you wanna add a couple of similar warnings to the project?

Needless to repeat, _USE_32BIT_TIME_T is not supported.



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