Rust-bindgen: Both _WIN32 and _WIN64 are defined when targeting 32-bit windows from 64-bit windows

[liranringel]

I tried to investigate https://github.com/rust-lang-nursery/rust-bindgen/issues/541 and found out that both _WIN32 and _WIN64 are defined. I could see how it makes many troubles, and perhaps related to that issue .
It won't happen if the command has the --target=i686-pc-windows-msvc flag, but it does happen if it has the --target=x86_64-pc-windows-msvc flag.
It also happens when I use bindgen through build.rs script (this way it happens on both cargo run --target=i686-pc-windows-msvc and cargo run --target=x86_64-pc-windows-msvc).

Input C/C++ Header

// example.h
#ifdef _WIN32
typedef int type1;
#endif
#ifdef _WIN64
typedef long long type2;
#endif

Bindgen Invocation

bindgen.exe example.h

Actual Results

pub type type1 = ::std::os::raw::c_int;
pub type type2 = ::std::os::raw::c_longlong;

Expected Results

// when --target=i686-pc-windows-msvc

pub type type1 = ::std::os::raw::c_int;

// when --target=x86_64-pc-windows-msvc

pub type type2 = ::std::os::raw::c_longlong;

[fitzgen]

Thanks for the bug report!

I'm not really familiar with windows development, but to be clear, only one of either _WIN32 or _WIN64 should ever be defined at once, right?

[petrochenkov]

_WIN32 is always defined these days (on both 32 and 64 bit targets), see https://msdn.microsoft.com/en-us/library/b0084kay.aspx

_WIN32 Defined as 1 when the compilation target is 32-bit ARM, 64-bit ARM, x86, or x64. Otherwise, undefined.
_WIN64 Defined as 1 when the compilation target is 64-bit ARM or x64. Otherwise, undefined.

32 here is supposed to be the opposite to 16, not 64.

[fitzgen]

_WIN32 is always defined these days (on both 32 and 64 bit targets), see https://msdn.microsoft.com/en-us/library/b0084kay.aspx

Does that mean that this issue can be closed as exhibiting expected behavior?

[liranringel]

Ah good to know.
Yet there is a problem, because through build.rs script _WIN64 is defined for 32bit.

[fitzgen]

To make sure I understand: the remaining issue is that when invoking bindgen as a library via build.rs on 32 bit host platforms, _WIN64 is still defined? But not when targeting 32-bit from 64 bit?

[liranringel]

No.
It happens on my 64 bit machine when targeting to 32 bit.
I don't know what happens on 32 bit hosts.

[fitzgen]

Thanks for the clarification!

[liranringel]

If I had to guess, I'd say it's related to https://github.com/rust-lang/rust/issues/42587
In other words, I guess that the bindgen library uses conditional compilation that misleads it because it's executed on a process that is 64 bit (like the build host).

[liranringel]

Update:
It happens on version 0.30, but it's working as expected on master.

[liranringel]

Ok I used git bisect to find the commit that solved it and it's https://github.com/rust-lang-nursery/rust-bindgen/commit/26da3447a73d0364849f0325f222c4a8c9337550
Makes sense that it solved it because it implements find_effective_target.

Only need to publish a new version.

[fitzgen]

We'll publish a new version after merging https://github.com/rust-lang-nursery/rust-bindgen/pull/1042