Re: [avr-gcc-list] __builtin_avr_delay_cycles expects an integer constant.

[Georg-Johann Lay]

Victor Aprea schrieb:

> I'm (at long last) trying to switch from using Windows to using Ubuntu for
> my AVR development. I'm using AVR-GCC 4.5.3 on Ubuntu 12.04. I'm using the
> Eclipse IDE with the AVR-GCC plugin. I'm getting the following error trace
> from the compiler:
>
> In file included from ../soft_uart.c:16:0:
> /usr/lib/gcc/avr/4.5.3/../../../avr/include/util/delay.h: In function
> ‘soft_uart_init’:
> /usr/lib/gcc/avr/4.5.3/../../../avr/include/util/delay.h:153:28: error:
> __builtin_avr_delay_cycles expects an integer constant.
> /usr/lib/gcc/avr/4.5.3/../../../avr/include/util/delay.h: In function
> ‘delay_bit_time’:
> /usr/lib/gcc/avr/4.5.3/../../../avr/include/util/delay.h:230:28: error:
> __builtin_avr_delay_cycles expects an integer constant.
>
> line 16 of soft_uart.c is just the #include <util/delay.h> line.
>
> I use _delay_ms and _delay_us in exactly six lines of code. The first two
> are:
>
> _delay_ms(BIT_TIME_US * 2);
> _delay_us(BIT_TIME_US);
>
> which both depend on the following definitions:
>
> #define BAUD_RATE   2400
> #define BIT_TIME_US (1000000.0 / BAUD_RATE)
>
> and then also the following four lines:
>
> _delay_ms(100);
> _delay_ms(250);
> _delay_ms(500);
> _delay_ms(2000);
>
> I've read this 
> thread<http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=105891&start=0>on
> avr-freaks and also this
> bug-report<http://old.nabble.com/-bug--34278--Seemingly-overzealous-%22__builtin_avr_delay_cycles-expects-an-integer-constant%22-td32451670.html>,
> but nothing jumps out at me as being relevant. Obviously, my arguments are
> all well defined constants at compile-time. The same error message shows up
> as long as at least one of those six lines is not commented out.
>
> Every single avr-gcc call issued by Eclipse contains the argument
> -DF_CPU=3686400UL so F_CPU is also a well defined constant. What the heck
> is going on here?

Without more information it's not possible to tell.

Can you post a preprocessed code for a (minimal) example that still
triggers the error, together with the error message and compiler
output? You get both by adding -save-temps -v to compiler options.
The preprocessed code is a text file named *.i

As the error message requestst an /integer/ constant:
Does the error disappear if you avoid float constants?

Johann

> Regards,
>
> Vic