Compilation fails when including complex.h

[wkjung]

Hi.

With nvcc V11.0.194 (g++ -v outputs (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0), I tried to compile the code below:
a.cu

#include <complex.h>
#include <thrust/copy.h>

But I got these errors:

~/thrust/thrust/iterator/constant_iterator.h(220): error #40: expected an identifier
~/thrust/thrust/iterator/constant_iterator.h(222): error #79: expected a type specifier
~/thrust/thrust/iterator/constant_iterator.h(222): error #79: expected a type specifier

Is it a bug or intended behavior? Thanks.

[alliepiper]

That's troubling.

It does seem to compile if the headers are reversed as a work around:

$ cat a.cu
#include <thrust/copy.h>
#include <complex.h>

$ nvcc -c tt.cu; echo $?
0

[dkolsen-pgi]

<complex.h> defines a macro named I, which represents the unit imaginary number. That clashes with any uses of the identifier I in any code after the include of <complex.h>. It would be good if Thrust were changed to not use the identifier I anywhere. There are not a lot, and the change should be simple, but there are several files in addition to <thrust/iterator/constant_iterator.h>.

[alliepiper]

Thanks for the explanation, @dkolsen-pgi, I'm surprised I've never encountered that before.

We should fix this at some point.