error: array type has incomplete element type xnn_timestamp (struct timespec branch)

[Nick-infinity]

          Hello @alankelly @wei-v-wang , How can we fix this issue if we are sticking to ubuntu 16 & gcc 5.4.0 ? I have tried #define _POSIX_C_SOURCE 199309L as suggested by @alankelly but it doesn't work.

Originally posted by @Nick-infinity in #2993 (comment)

[Nick-infinity]

Hello @alankelly @wei-v-wang , How can we fix this issue if we are sticking to ubuntu 16 & gcc 5.4.0 ? I have tried #define _POSIX_C_SOURCE 199309L as suggested by @alankelly but it doesn't work.

[gtkramer]

It looks like src/xnnpack/subgraph.{c,h} tries to use timespec from time.h, but this was something introduced in C11. Maybe if you replace CMAKE_C_STANDARD 99 with CMAKE_C_STANDARD 11 in the root CMakeLists.txt that will work? We do that when we compile PyTorch and it builds successfully in that case. This seems like a bug in the build system though that should be fixed and require C11, but I'd be interested in getting input from the project maintainers on this.

https://en.cppreference.com/w/c/chrono/timespec

[gtkramer]

Though with an old compiler like GCC 5.4, support for C11 may not be complete. But give it a try?