Bug 34734

after upgrading to WinAVR-20071221 my C++ projects trigger the same warning message.

for completeness, my sources look like:


// usb_user_device_descriptor
PROGMEM S_usb_device_descriptor usb_dev_desc =
  {
    sizeof( usb_dev_desc ), DEVICE_DESCRIPTOR,
    U_WORD( USB_SPECIFICATION ), DEVICE_CLASS,
    DEVICE_SUB_CLASS, DEVICE_PROTOCOL, EP_CONTROL_LENGTH,
    U_WORD( VENDOR_ID ),
    U_WORD( PRODUCT_ID ),
    U_WORD( RELEASE_NUMBER ), STRING_INDEX_MAN, STRING_INDEX_PROD,
    STRING_INDEX_SN, NB_CONFIGURATION
  };

Liviu

version 4.2.1 seems to be affected as well:

--------------------------------------------
holger@x:~/scratch$ cat foo.cpp
#include <avr/pgmspace.h>

const int foobar1 = 42;
int foobar2 = 42;
const int PROGMEM foobar3 = 42;
int PROGMEM foobar4 = 42;

holger@x:~/scratch$ avr-g++ -Wall -mmcu=atmega1281 -c foo.cpp
foo.cpp:5: warning: only initialized variables can be placed into program memory area
foo.cpp:6: warning: only initialized variables can be placed into program memory area
holger@x:~/scratch$ avr-g++ --version
avr-g++ (GCC) 4.2.1 (SUSE Linux)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

*** Bug 40112 has been marked as a duplicate of this bug. ***

I found a way to place data in program memory for C++ without producing the annoying warnings. The trick is omiting __attribute__((__progmem__)) and instead always use __attribute__((section(".progmem.something"))) for placing your data into a special section beginning with ".progmem.". I tested this with different avr-g++ compiler versions (3.4.4, 4.1.1, 4.2.1, 4.3.3, 4.4.0, and 4.4.3), and it always results in the desired behavior.

Example:
[mschulze@teeth tst]$ cat progmem.cpp 
static char __attribute((section(".progmem.something"))) str[]="program memory data";

const char* test() {
    return str;
}
[mschulze@teeth tst]$ /usr/bin/avr-g++ -Wall -mmcu=atmega1281 -c progmem.cpp 
[mschulze@teeth tst]$ /usr/bin/avr-g++ --version
avr-g++ (GCC) 4.3.3
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[mschulze@teeth tst]$ 

Regards,
Michael

same problem in 4.5.2.
Maybe importance of this bug should be increased? Imho it's a little bit embarrassing to keep this bug so long... (since 2008, over 3 yrs!)

regards

Author: gjl
Date: Wed Jun 29 07:57:25 2011
New Revision: 175621

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175621
Log:
	PR target/34734
	* config/avr/avr.c (avr_handle_progmem_attribute): Move warning 
	about uninitialized data attributed 'progmem' from here...
	(avr_encode_section_info): ...to this new function.
	(TARGET_ENCODE_SECTION_INFO): New define.
	(avr_section_type_flags): For data in ".progmem.data", remove
	section flag SECTION_WRITE.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/avr/avr.c

Author: gjl
Date: Thu Jun 30 13:28:43 2011
New Revision: 175705

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175705
Log:
	
	PR target/34734
	Backport from mainline
	* config/avr/avr.c (avr_handle_progmem_attribute): Move warning 
	about uninitialized data attributed 'progmem' from here...
	(avr_encode_section_info): ...to this new function.
	(TARGET_ENCODE_SECTION_INFO): New define.
	(avr_section_type_flags): For data in ".progmem.data", remove
	section flag SECTION_WRITE.


Modified:
    branches/gcc-4_6-branch/gcc/ChangeLog
    branches/gcc-4_6-branch/gcc/config/avr/avr.c

Closed as resolved+fixed.

(In reply to comment #5)
> same problem in 4.5.2.
> Maybe importance of this bug should be increased? Imho it's a little bit
> embarrassing to keep this bug so long... (since 2008, over 3 yrs!)
> regards

Increasing importance won't help.  The only thing that would help is increasing number of people that are inclined to improve avr-gcc.

regards

Note that progmem on types is not documented an not supposed to work at all.

Author: gjl
Date: Thu Jun 30 13:45:04 2011
New Revision: 175706

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175706
Log:
	PR target/34734
	Backport from mainline
	(avr_section_type_flags): For data in ".progmem.data", remove
	section flag SECTION_WRITE.

Modified:
    branches/gcc-4_6-branch/gcc/ChangeLog
    branches/gcc-4_6-branch/gcc/config/avr/avr.c

Author: gjl
Date: Mon Jul  4 12:48:04 2011
New Revision: 175811

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175811
Log:
	PR target/34734
	PR target/44643
	* gcc.target/avr/avr.exp: Run over cpp files, too.
	* gcc.target/avr/torture/avr-torture.exp: Ditto.
	* gcc.target/avr/progmem.h: New file.
	* gcc.target/avr/exit-abort.h: New file.
	* gcc.target/avr/progmem-error-1.c: New file.
	* gcc.target/avr/progmem-error-1.cpp: New file.
	* gcc.target/avr/progmem-warning-1.c: New file.
	* gcc.target/avr/torture/progmem-1.c: New file.
	* gcc.target/avr/torture/progmem-1.cpp: New file.


Added:
    trunk/gcc/testsuite/gcc.target/avr/exit-abort.h
    trunk/gcc/testsuite/gcc.target/avr/progmem-error-1.c
    trunk/gcc/testsuite/gcc.target/avr/progmem-error-1.cpp
    trunk/gcc/testsuite/gcc.target/avr/progmem-warning-1.c
    trunk/gcc/testsuite/gcc.target/avr/progmem.h
    trunk/gcc/testsuite/gcc.target/avr/torture/progmem-1.c
    trunk/gcc/testsuite/gcc.target/avr/torture/progmem-1.cpp
Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.target/avr/avr.exp
    trunk/gcc/testsuite/gcc.target/avr/torture/avr-torture.exp