bugAVR C Runtime Library - Bugs: bug #27201, _WORDREGISTER in xmega headers...


bug #27201: _WORDREGISTER in xmega headers does not work in C99 mode

Submitted by:  Soeren Schneider <schneiso>
Submitted on:  Fri 07 Aug 2009 10:41:28 AM UTC  
Category:  Header Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Header files
Status:  Fixed Assigned to:  Eric Weddington <arcanum>
Percent Complete:  100% Open/Closed:  Closed
Release:  1.6.5 Fixed Release:  1.6.3

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Mon 31 Aug 2009 11:49:09 PM UTC, comment #2: 

Ok, finally committed.

Eric Weddington <arcanum>
Project AdministratorIn charge of this item.
Fri 07 Aug 2009 10:52:35 AM UTC, comment #1: 

The problem is that accessing the union (and also struct,
for byte-wide access) elements without naming the union
itself is a GCC extension, so it is turned off when compiling
with -std=c99.

It appears to me that prepending the entire union declaration
with _extension_ does fix it by telling GCC "It's OK to use
the following GCC extension here, regardless of the --std
option in effect".

Joerg Wunsch <joerg_wunsch>
Project Administrator
Fri 07 Aug 2009 10:41:28 AM UTC, original submission:  

When using -std=c99 in conjunction with ATxmega128A1 the following example code from the website for Xmega (Application node AVR1300: Using the XMEGA ADC) does not compile for avr-gcc (Win-AVR20090313).

ADC_CH_t *acd_ch;
int16_t answer;
answer = adc_ch->RES;

This creates the following error message:
"error: 'ADC_CH_t' has no member named 'RES'

When looking at the corresponding header file iox128a1.h the type ADC_CH_t is defined as such:

typedef struct ADC_CH_struct
    register8_t CTRL;  /* Control Register */
    register8_t MUXCTRL;  /* MUX Control */
    register8_t INTCTRL;  /* Channel Interrupt Control */
    register8_t INTFLAGS;  /* Interrupt Flags */
    _WORDREGISTER(RES);  /* Channel Result */
    register8_t reserved_0x6;
    register8_t reserved_0x7;
} ADC_CH_t;

The issue is caused be the definition of "_WORDREGISTER" in line 94:

#define _WORDREGISTER(regname)   \
    union \
    { \
        register16_t regname; \
        struct \
        { \
            register8_t regname ## L; \
            register8_t regname ## H; \
        }; \

This does not work for C99, which (unfortunately) I need for my project.

The code works with IAR Workbench 5.30.02.

Soeren Schneider <schneiso>


(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

Attached Files
file #18587:  ChangeLog added by aboyapati (37KiB - text/plain - _WORDREGISTER defined for xmega headers)
file #18586:  NEWS added by aboyapati (37KiB - text/plain - _WORDREGISTER defined for xmega headers)
file #18585:  bug27201.patch added by aboyapati (12KiB - application/octet-stream - _WORDREGISTER defined for xmega headers)


Depends on the following items: None found

Items that depend on this one: None found


Carbon-Copy List
  • -email is unavailable- added by arcanum (Updated the item)
  • -email is unavailable- added by aboyapati (Updated the item)
  • -email is unavailable- added by joerg_wunsch (Posted a comment)
  • -email is unavailable- added by schneiso (Submitted the item)



    Follow 14 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2009-08-31 arcanum Open/ClosedOpen => Closed
        StatusNone => Fixed
        Percent Complete90% => 100%
    2009-08-30 arcanum Open/ClosedClosed => Open
        StatusFixed => None
        Percent Complete100% => 90%
    2009-08-26 arcanum StatusNone => Fixed
        Percent Complete0% => 100%
        Assigned toNone => arcanum
        Open/ClosedOpen => Closed
        Fixed ReleaseNone => 1.6.3
    2009-08-17 aboyapati Attached File- => Added ChangeLog, #18587
        Attached File- => Added bug27201.patch, #18585
        Attached File- => Added NEWS, #18586

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