Nested Functions on Android NDK

Question

Is there a way to use nested functions on the the Android NDK? It should be possible, since the NDK uses gcc right?

Well I tried defining a function inside main, and the compiler simply doesn't recognize it. Here's the error

error: a function-definition is not allowed here before '{' token error: expected '}' at end of input

Answer 1

I don't know exactly. But as far as NDK uses arm gcc compiler and that nested functions may be broken on ARM architecture - my best guess is that nested functions may be disabled in NDK toolset. In any way - nested functions is GCC extension, so if you want your code to be portable you better don't use gcc extensions at all and use C89/C90 compatible code instead.

Answer 2

The nested functions example from here, where a foo() contains a square(), compiles and runs fine (on a Tegra 3). I use the NDK r8 android toolchain (with android-cmake, if that makes any difference, which shouldn't be the case). Maybe you should try with r8 in case you use an older version?

Answer 3

Yes, it should be possible. You may need to add the -fnested-functions flag to gcc calls.

Answer 4

Nested functions require an executable stack, which is disabled by default in Android.

It took me an unbelievable amount of time to figure it out - but you need to add the following to your CFLAGS:

-z execstack -Wa,--execstack

All the best!