Project targeting AVR and Due

Hardware Arduino Due
6

I can't this to work. My sketch is:

#include "sub/mydriver.c"

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly: 
  myfunc(2);
}

sub/mydriver.c :

int  myfunc (int a)
{
	return a*a;
}

The compiler output is :

C:\Programs\arduino-1.5.2\hardware\tools\avr\bin\avr-g++ -c -g -Os -w -fno-exceptions -ffunction-sections -fdata-sections -MMD -mmcu=atmega1280 -DF_CPU=16000000L -DARDUINO=152 -IC:\Programs\arduino-1.5.2\hardware\arduino\avr\cores\arduino -IC:\Programs\arduino-1.5.2\hardware\arduino\avr\variants\mega C:\Users\bob\AppData\Local\Temp\build2805575431420087737.tmp\sketch_feb16b.cpp -o C:\Users\bob\AppData\Local\Temp\build2805575431420087737.tmp\sketch_feb16b.cpp.o 
sketch_feb16b.ino:2:26: error: sub/mydriver.c: No such file or directory
sketch_feb16b.ino: In function 'void loop()':
sketch_feb16b:11: error: 'myfunc' was not declared in this scope

Using Arduino 1.5.2. I am doing something dumb?

ETA: I though that using chevron quotes #include <sub/mydriver.c> was finding the file but not compiling it, but in fact the include is ignored completely, and doesn't complain about missing files.

ETA2: Yes, I realize the above is from the AVR compiler, but the same applies for the ARM compiler. See below :wink: