[BUG] sys/socket.h should not declare SOCK_CLOEXEC and SOCK_NONBLOCK before __ANDROID_API__ >= 21

[guillaume-michel]

Description

NDK's sys/socket.h defines SOCK_CLOEXEC and SOCK_NONBLOCK unconditionally but it can only be used by accept4 syscall which is guarded by ANDROID_API >= 21.

Some application may check if SOCK_CLOEXEC and SOCK_NONBLOCK are defined to decide if they can use accept4 or if they should fallback to accept. If SOCK_CLOEXEC and SOCK_NONBLOCK are defined but not accept4, you get an error when compiling for API level < 21.

Possible solution:
Adding a guard ANDROID_API >= 21 for the defines SOCK_CLOEXEC and SOCK_NONBLOCK will prevents such error.

Environment Details

• NDK Version: 21.3.6528147
• Build system: any (not related to build system)
• Host OS: any (not related to host OS)
• ABI: Android 19
• NDK API level: 19
• Device API level: 19

[DanAlbert]

Having a low minSdkVersion but using new APIs via dlsym is common. If we hide the constants you can't do that.

Some application may check if SOCK_CLOEXEC and SOCK_NONBLOCK are defined to decide if they can use accept4

Those applications should check for accept4 if they want to know if accept4 is available.